Microchip Technology MCP401X, MCP402X User’s Guide

MCP401X/2X

Digital Potentiometer

Evaluation Board

User’s Guide

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®

8-bit MCUs, KEEL

®

OQ

code hopping

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Tabl e of Conten ts

Preface ........................................................................................................................... 1

Chapter 1. Product Overview

1.1 Introduction ..................................................................................................... 5

1.2 What is the MCP402X Digital Potentiometer Evaluation Board? ................... 5

1.3 What the MCP402X Digital Potentiometer Evaluation Board Kit Includes ..... 6

Chapter 2. Installation and Operation

2.1 Introduction ..................................................................................................... 7

2.2 PCB Description ............................................................................................. 7

2.3 Test and Operating Instructions ................................................................... 10

2.4 Firmware Description ................................................................................... 17

Appendix A. Schematic and Layouts

A.1 Introduction .................................................................................................. 19

A.2 Schematic .................................................................................................. 20

A.3 MCP402X Board Layout – Top Layer + Silk-screen ................................. 21

A.4 MCP402X Board Layout – Bottom Layer ................................................. 21

A.5 MCP402X Board Layout – Top Silkscreen ............................................... 22

A.6 MCP402X Board Layout – Bottom Layer + Silk-screen ........................... 22

Appendix B. Bill Of Materials (BOM) Appendix C. Using the BFMP Programmer to Power the Board

C.1 Powering the Board Using the BFMP Programmer ..................................... 25

Appendix D. Potential Programming Issue of the MCP402XEV

D.1 Introduction .................................................................................................. 27

Appendix E. 00066_MCP402XEV.ASM Source Code

E.1 Introduction .................................................................................................. 29

Worldwide Sales and Service .................................................................................... 42

MCP401X/2X Evaluation Board User’s Guide

NOTES:

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Preface

NOTICE TO CUSTOMERS

All documentation becomes dated, and this manual is no exception. Microchip tools and documentation are constantly evolving to meet customer needs, so some actual dialogs and/or tool descriptions may differ from those in this document. Please refer to our web site (www.microchip.com) to obtain the latest documentation available.

Documents are identified with a “DS” number. This number is located on the bottom of each page, in front of the page number. The numbering convention for the DS number is “DSXXXXXA”, where “XXXXX” is the document number and “A” is the revision level of the document.

INTRODUCTION

This chapter contains general information that will be useful to know before using the MCP402X Digital Potentiometer Evaluation Board. Items discussed in this chapter include:

• Document Layout

• Conventions Used in this Guide

• Recommended Reading

• The Microchip Web Site

• Customer Support

• Document Revision History

DOCUMENT LAYOUT

This document describes how to use the MCP402X Digital Potentiometer Evaluation Board. The manual layout is as follows:

• Chapter 1. “Product Overview” – Important information about the MCP402X

Digital Potentiometer Evaluation Board.

• Chapter 2. “Installation and Operation” – Includes instructions on how to get

started with this evaluation board.

• Appendix A. “Schematic and Layouts” – Shows the schematic and layout

diagrams for the MCP402X Digital Potentiometer Evaluation Board.

• Appendix B. “Bill Of Materials (BOM)” – Lists the parts used to build the

MCP402X Digital Potentiometer Evaluation Board.

• Appendix C. “Using the BFMP Programmer to Power the Board” – Shows

how to interface the BFMP board with the MCP402X Digital Potentiometer Evaluation Board.

• Appendix D. “Potential Programming Issue of the MCP402XEV” – Discusses

possible programming issues with Rev 1 and Rev 2 of the MCP402X Digital Potentiometer Evaluation Board.

• Appendix E. “00066_MCP402XEV.ASM Source Code” – Provides information

about the application firmware, as well as the location of the source code.

MCP401X/2X Evaluation Board User’s Guide

CONVENTIONS USED IN THIS GUIDE

This manual uses the following documentation conventions:

DOCUMENTATION CONVENTIONS

Description Represents Examples

Arial font:

Italic characters Referenced books

Emphasized text ...is the

Initial caps A window the Output window

A dialog the Settings dialog A menu selection select Enable Programmer

Quotes A field name in a window or

dialog

Underlined, italic text with right angle bracket

Bold characters A dialog button Click OK

‘b

nnnn

Text in angle brackets < > A key on the keyboard Press <Enter>, <F1>

Courier New font:

Plain Courier New Sample source code #define START

Italic Courier New A variable argument file.o, where file can be

0xnnnn A hexadecimal number where

Square brackets [ ] Optional arguments mcc18 [options] file

Curly brackets and pipe character: { | }

Ellipses... Replaces repeated text var_name [,

A menu path

A tab Click the Power tab A binary number where n is a

digit

Filenames autoexec.bat File paths c:\mcc18\h Keywords _asm, _endasm, static Command-line options -Opa+, -Opa- Bit values 0, 1

n is a hexadecimal digit

Choice of mutually exclusive arguments; an OR selection

Represents code supplied by user

MPLAB® IDE User’s Guide

“Save project before build”

File>Save

‘b00100, ‘b10

any valid filename

0xFFFF, 0x007A

[options] errorlevel {0|1}

var_name...] void main (void)

{ ... }

only

compiler...

THE MICROCHIP WEB SITE

Microchip provides online support via our web site at www.microchip.com. This web site is used as a means to make files and information easily available to customers. Accessible by using your favorite Internet browser, the web site contains the following information:

• Product Support – Data sheets and errata, application notes and sample

programs, design resources, user’s guides and hardware support documents, latest software releases and archived software

• General Technical Support – Frequently Asked Questions (FAQs), technical

support requests, online discussion groups, Microchip consultant program member listing

• Business of Microchip – Product selector and ordering guides, latest Microchip

press releases, listing of seminars and events, listings of Microchip sales offices, distributors and factory representatives

CUSTOMER SUPPORT

Users of Microchip products can receive assistance through several channels:

• Distributor or Representative

• Local Sales Office

• Field Application Engineer (FAE)

• Technical Support

• Development Systems Information Line Customers should contact their distributor, representative or field application engineer

(FAE) for support. Local sales offices are also available to help customers. A listing of sales offices and locations is included in the back of this document.

Technical support is available through the web site at: http://support.microchip.com

Preface

DOCUMENT REVISION HISTORY

Revision B (December 2005)

• Updated to include MCP401X devices

• Enhancement of Operation Description

• Added Appendix C. “Using the BFMP Programmer to Power the Board” -

Programming the MCP402X Digital Potentiometer Evaluation Board

• Added Appendix D. “Potential Programming Issue of the MCP402XEV”- A

description of potential programming issues (and their solutions) with the MCP402X Digital Potentiometer Evaluation Board

Revision A (April 2005)

• Initial Release of this Document

MCP401X/2X Evaluation Board User’s Guide

NOTES:

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Chapter 1. Product Overview

1.1 INTRODUCTION

This chapter provides an overview of the MCP402X Digital Potentiometer Evaluation Board and covers the following topics:

• What is the MCP402X Digital Potentiometer Evaluation Board?

• What the MCP402X Digital Potentiometer Evaluation Board includes

1.2 WHAT IS THE MCP402X DIGITAL POTENTIOMETER EVALUATION BOARD?

The MCP402X Digital Potentiometer Evaluation Board (MCP402XEV) allows the system designer to quickly evaluate the operation of Microchip Technology’s MCP401X/2X Digital Potentiometer products.

The MCP402X Digital Potentiometer Evaluation Board PCB was designed to support:

• 8-pin, 150 mil SOIC MCP4021-XXX/SN devices

• SOT-23-6 MCP4022-XXX/OT devices

• SOT-23-6 MCP4023-XXX/OT devices

• SOT-23-5 MCP4024-XXX/OT devices

• 8-pin, 150 mil SOIC MCP4011-XXX/SN devices

• SOT-23-6 MCP4012-XXX/OT devices

• SOT-23-6 MCP4013-XXX/OT devices

• SOT-23-5 MCP4014-XXX/OT devices In addition to supporting the MCP401X/2X, the MCP402XEV also utilizes the SOT-23-6

PIC10F20X microcontroller. The PIC10F20X is supplied with example firmware that debounces the INCR and

DECR push buttons and generates the simple U/D MCP401X/2X to increment and decrement the potentiometer’s wiper. It also generates the simple U/D potentiometer’s wiper.

protocol required by the MCP402X to lock and unlock the

protocol required by the

MCP401X/2X Evaluation Board User’s Guide

1.3 WHAT THE MCP402X DIGITAL POTENTIOMETER EVALUATION BOARD KIT

INCLUDES

This MCP402X Digital Potentiometer Evaluation Board Kit includes:

• One populated Printed Circuit Board (PCB)

- MCP4021-103/OT

- PIC10F206-I/OT with 00066_MCP402XEV.HEX programmed into memory

- Two push button switches: one for Increment commands (INCR), one for Decrement commands (DECR)

- Decoupling capacitors

- 5 resistors to isolate the switches and create a voltage divider with the MCP4021-103/OT

• One blank PCB to allow rapid prototyping of a specific digital potentiometer configuration

• 2 samples each of the MCP4021-202/OT, MCP4021-502/OT, MCP4021-103/OT and MCP4021-503/OT

• 1 PIC10F20X-I/OT sample

• MCP401X/2X Digital Potentiometer Evaluation Board User’s Guide (electronic version on CD) (DS51546)

Chapter 2. Installation and Operation

2.1 INTRODUCTION

The MCP402X Digital Potentiometer Evaluation Board provides a tested, out-of-the-box example of a MCP401X/2X application. The circuit description is described in Section 2.2 “PCB Description”, while the test and operating instructions are described in Section 2.3 “Test and Operating Instructions”. A supplied blank PCB allows rapid prototyping of the designer’s specific MCP401X/2X device, along with other desired passive components (resistor and capacitors) and connection posts.

2.2 PCB DESCRIPTION

The MCP402X Digital Potentiometer Evaluation Board has the following features:

• 150 mil, 8-pin SOIC pinout (U1) supports the MCP4021 and MCP4011 devices

• SOT-23-6 pinout (U2) supports the MCP4022/23/24 and MCP4012/13/14 devices

• SOT-23-6 pinout (U3) supports the PIC10F20X devices

• Connection terminals can be left unpopulated for easy connection using small alligator clip leads (clamped across the edge of the board) or populated with either through-hole or surface-mount terminals

• Footprints for optional passive components for:

- Power supply filtering

- Device bypass capacitor

- Terminal “A” pull-up resistor

- Terminal “B” pull-down resistor

• Footprints for two switches:

- INCR button operation can be detected by the PIC10F20X to generate

Increment commands (move wiper toward terminal A)

- DECR button operation can be detected by the PIC10F20X to generate

Decrement commands (move wiper toward terminal B)

• Button sequence instructions are printed on the back of the PCB

Appendix A.2 “Schematic” illustrates the schematic for the MCP402XEV.

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Note: The PIC10F20X firmware (00066_MCP402XEV.HEX) must be

programmed into the microcontroller before the MCP402XEV is functional.

MCP401X/2X Evaluation Board User’s Guide

2.2.1 Evaluating the MCP4021 and MCP4011

The MCP4021/11-XXXI/SN is an 8-pin digital potentiometer device with terminals A, B and W available on the device pins. Footprint U1 supports the 150 mil SOIC package. Resistors R2 and R3 are 2.5 k MCP4021-103I/SN digital potentiometer. This creates a “windowed” voltage divider with a transfer function illustrated in Equation 2-1.

EQUATION 2-1: WINDOWED POTENTIOMETER – VOLTAGE DIVIDER

CALCULATION

V

wiper

Note 1: DO NOT populate U2 if using U1.

2: The MCP4011 has high-voltage tolerant pins and, therefore, accepts

high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

Ω on the populated PCB, along with the 10 kΩ

V

DDRwb

------------------------------------------R2 R3 R

++

R3+()⋅

5.0V d 10k

---------------------------------------------------------------------

==

nom

⋅

()63⁄2.5k+()

⋅

2.5k 2.5k 10k++

Where:

d = the wiper setting (0 to 63)

2.2.2 Evaluating the MCP4022 and MCP4012

The MCP4022/12-XXXI/OT is a 6-pin, stand-alone digital rheostat with terminals A and W available on the device pins. Footprint U2 supports the SOT-23-6 package. An “INCR” command moves the wiper toward terminal A, thus causing the resistance across the rheostat to decrease. A “DECR” command moves the wiper toward terminal B, thus causing the resistance across the rheostat to increase.

Note 1: DO NOT populate U1 if using U2.

2: The included MCP4021 digital potentiometer samples could be used to

evaluate the MCP4022 simply by not populating R3 and letting terminal B float.

3: The MCP4012 has high-voltage tolerant pins and, therefore, accepts

high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

Installation and Operation

2.2.3 Evaluating the MCP4023 and MCP4013

The MCP4023/13-XXXI/OT is a 6-pin, grounded digital potentiometer with terminals A and W available on the device pins. Footprint U2 supports the SOT-23-6 package. Populating R2 will create a voltage divider with a transfer function illustrated in Equation 2-2.

EQUATION 2-2: GROUNDED POTENTIOMETER – VOLTAGE DIVIDER

CALCULATION

V

wiper

VDDRwb⋅

-------------------------R2 R

+

5.0V d 10k

-----------------------------------------------

==

nom

Where:

d = the wiper setting (0 to 63)

Note 1: DO NOT populate U1 if using U2.

2: The included MCP4021 digital potentiometer samples could be used to

evaluate the MCP4023 simply by shorting terminal B to GND.

3: The MCP4013 has high-voltage tolerant pins and, therefore, accepts

high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

⋅63⁄

()

⋅

2.5k 10k+

2.2.4 Evaluating the MCP4024 and MCP4014

The MCP4024/14-xxxI/OT is a 5-pin, grounded digital rheostat with the W terminals available on the device pins. Footprint U2 supports the SOT-23-5 package. An “INCR” command moves the wiper toward terminal A, thus causing the resistance across the rheostat to increase. A “DECR” command moves the wiper toward terminal B, thus causing the resistance across the rheostat to decrease.

Note 1: DO NOT populate U1 if using U2.

2: The included MCP4021 digital potentiometer samples could be used to

evaluate the MCP4024 simply by not populating R float and by shorting terminal B to GND.

3: The MCP4014 has high-voltage tolerant pins and, therefore, accepts

high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

, letting terminal A

2

MCP401X/2X Evaluation Board User’s Guide

2.3 TEST AND OPERATING INSTRUCTIONS

The populated PCB is configured to create a voltage divider from VDD to VSS using a

2.5 kΩ pull-up resistor (R2), the MCP4021-103I/SN (10 kΩ) and a 2.5 kΩ pull-down resistor (R3). To quickly evaluate the digital potentiometer’s performance, the following test equipment is required:

• 2.7V to 5.5V power supply

• Voltmeter or Digital Multimeter (DMM) Figure 2-1 shows the Digital Potentiometer Evaluation Board PCB, components and

the connection points that will be used in the step-by-step demonstration.

Increment (INCR) Switch

Resistor R2 (A to VDD)

Baseline Flash MCU Programmer (BFMP) Interface

Resistor R3 (B to GND)

Decrement (DECR) Switch

FIGURE 2-1: Digital Potentiometer Evaluation Board Overview.

Digital Potentiometer Node A Pad

Digital Potentiometer Node B Pad

Digital Potentiometer Wiper W Pad

Installation and Operation

2.3.1 Test Setup

1. Connect the power supply “+” to VDD and the “–” to GND.

2. Connect the voltmeter to the W terminal and GND. The voltmeter should reflect the wiper setting with respect to Equation 2-3.

EQUATION 2-3: POPULATED PCB – VOLTAGE DIVIDER CALCULATION

V

DDRwb

V

wiper

------------------------------------------R2 R 3 R

++

Where:

d = the wiper setting (0 to 63)

Using R2 and R3 = 2.5 kΩ:

• If a 2 kΩ MCP4021 is utilized, the output range will be approximately 1.79V to

3.21V.

• If a 5 kΩ MCP4021 is utilized, the output range will be approximately 1.25V to

3.75V.

• If a 10 kΩ MCP4021 is utilized, the output range will be approximately 0.83V to

4.17V.

• If a 50 kΩ MCP4021 is utilized, the output range will be approximately 0.23V to

4.77V.

R3+()⋅

5.0V d 10k

---------------------------------------------------------------------

==

AB

⋅

()63⁄2.5k+()

⋅

2.5k 2.5k 10k++

MCP401X/2X Evaluation Board User’s Guide

2.3.2 MCP402X Digital Potentiometer Evaluation Board Firmware Operation

The 00066_MCP402XEV.HEX firmware programmed into the PIC10F20X provides a very simple interface to operate the MCP402X digital potentiometer. There are ten basic commands supported for the user to exercise the MCP402X digital potentiometer.

Table 2-1 shows the firmware commands of the Digital Potentiometer Evaluation Board.

MCP401X/2X Evaluation Board User’s Guide

#4

(Release)

#3

(Release)

(5)

#2

(Depress)

(5)

#1

(Depress)

INCR/DECR

MCP401x will

Wiper is “locked”

Works when

“unlocked”

INCR DECR

(for < 2 sec)

DECR INCR

(for < 2 sec)

INCR DECR

(for > 2 sec)

voltage for the CS pin.

IHH MIN

After

Command

Wiper is

“locked”

CS

and U/D pins?

High Voltage on

) greater than 5.0V to allow the simple charge pump to generate the V

DD

Value in EEPROM

Saves Wiper

Yes No — — No Yes INCR (for > 2 sec) — — —

Yes No — — No Yes INCR (for < 2 sec)— ——

Yes Ye s — Yes Yes Ye s INCR (for < 2 sec) DECREMENT

Command Button Sequence

# of

Steps

(1)

Yes Yes Yes — Yes Yes INCR (for < 2 sec) DECREMENT

(1)

1

(6)

(2)

(6)

Yes Yes — Yes Yes Yes INCR (for < 2 sec) DECREMENT

Yes No — — No Yes DECR (for < 2 sec) — — —

(3)

64

(3)

(6)

Increment/Decrement -

(Low Voltage/High Voltage)

#

1 INCR - (Low Voltage) 1

3 INCR - (High Voltage)

2 INCR - (High Voltage)

4 INCR - (Low Voltage) 64

5 INCR - (High Voltage)

6 DECR - (Low Voltage) 1

TABLE 2-1: DIGITAL POTENTIOMETER EVALUATION BOARD FIRMWARE INCREMENT/DECREMENT COMMANDS

Yes No — — No Ye s DEC R (for > 2 sec)— — —

Yes Ye s Yes — Yes Ye s DECR (for < 2 sec) INCR (for < 2 sec) INCR DECR

(4)

1

9 DECR - (Low Voltage) 64

8 DECR - (High Voltage)

Yes Ye s — Yes Yes Ye s DECR (for < 2 sec) INCR (for > 2 sec) DECR INCR

(4)

64

(6)

10 DECR - (High Voltage)

Note 1: Move wiper W towards node A (Increment wiper 1 step).

Yes Yes — Yes Yes Yes DECR (for < 2 sec) INCR (for < 2 sec) DECR INCR

(3)

1

(6)

7 DECR - (High Voltage)

2: Move wiper W to node A (Increment wiper 64 steps). Forces the wiper setting to “full-scale” (wiper W = node A).

requires the INCR button to be depressed. Then, before 2 seconds elapses, the DECR button must be depressed. Next, before 2 seconds elapses, the INCR

button must be released. The DECR button can then be released.

3: Move wiper W towards node B (Decrement wiper 1 step).

4: Move wiper W to node B (Decrement wiper 64 steps). Forces the wiper setting to “zero scale” (wiper W = node B).

5: If there is more than one sequence, the button sequence #1 must continue to be held down while progressing to sequence #2. Example: Command # 2.

6: High-voltage commands require a system voltage (V

MCP401X/2X Evaluation Board User’s Guide

2.3.3 Running the Ratiometric Voltage Demo

Table 2-2 provides step-by-step instructions to perform a demonstration of the MCP402X Digital Potentiometer Evaluation Board. Measuring Ratiometric Voltage

TABLE 2-2: MEASURING RATIOMETRIC VOLTAGE

Step Action Result

1 Power up the populated Digital Potentiometer

Evaluation Board. Voltage calculations use a system voltage of 5V.

Board can be powered via a valid voltage (such as 5V) on the VDD and GND PCB Pads, or by connecting a BFMP programmer that is connected to an active PC’s USB port (powered via the USB connection).

2 Set DMM to measure the required voltage range

(0V to 5.5V). Connect the DMM ground connection to the evaluation board GND terminal and the DMM V/Ω connection to terminal W of the evaluation board.

3 Turn on DMM. On DMM:

4 On the Digital Potentiometer Evaluation Board:

Implement Command #5 (see Table 2-1).

5 On the Digital Potentiometer Evaluation Board:

Implement Command #4 (see Table 2-1).

6 On the Digital Potentiometer Evaluation Board:

Implement Command #6 (see Table 2-1).

7 On the Digital Potentiometer Evaluation Board:

Implement Command #6 (see Table 2-1) 15 more times.

8 On the Digital Potentiometer Evaluation Board:

Turn off/disconnect power supply.

9 On the Digital Potentiometer Evaluation Board:

Reapply power to Digital Potentiometer Evaluation Board.

10 On the Digital Potentiometer Evaluation Board:

Implement Command #3 (see Table 2-1).

—

DMM will display the voltage determined by the current non-volatile setting of the wiper.

On the Digital Potentiometer Evaluation Board: WiperLock™ Technology is disabled and the wiper is incremented from power-on position.

On DMM: Voltage increments approximately 0.05V.

On the Digital Potentiometer Evaluation Board: Wiper is forced to the full-scale position (Wiper W = node A).

On DMM: Voltage equals approximately 4.17V.

On the Digital Potentiometer Evaluation Board: Wiper is decremented one position from the full-scale position.

On DMM: Voltage equals approximately 4.12V.

On the Digital Potentiometer Evaluation Board: Wiper is decremented to the 25% position from node A (full-scale) to node B (zero-scale).

On DMM: Voltage equals approximately 3.33V.

On DMM: Voltage equals approximately 0V.

On DMM: Voltage equals approximately 3.33V. This shows that the MCP4021 retained the last selected wiper setting.

On the Digital Potentiometer Evaluation Board: Wiper is incremented one position and the wiper is locked (WiperLock Technology is enabled).

On DMM: Voltage equals approximately 3.38V.

Installation and Operation

TABLE 2-2: MEASURING RATIOMETRIC VOLTAGE (CONTINUED)

Step Action Result

11 On the Digital Potentiometer Evaluation Board:

Implement Command #1 (see Table 2-1).

12 On the Digital Potentiometer Evaluation Board:

Turn off/disconnect power supply.

13 On the Digital Potentiometer Evaluation Board:

Re-apply power to Digital Potentiometer Evaluation Board.

On the Digital Potentiometer Evaluation Board: Wiper is NOT moved due to the wiper being locked (WiperLock™ Technology is enabled).

On DMM: Voltage equals approximately 3.38V.

On DMM: Voltage equals approximately 0V.

On DMM: Voltage equals approximately 3.38V. This shows that the MCP4021 retained the last saved wiper setting.

MCP401X/2X Evaluation Board User’s Guide

2.3.4 Wiper Voltages

Table 2-3 shows the relation between the wiper position and the voltage on the wiper when 5.0 volts is applied to the MCP402X Digital Potentiometer Evaluation Board where the resistors R2 and R3 are 2500Ω and the MCP4011 resistor value (R 10 kΩ. Equation 2-4 shows the formula for these calculations.

EQUATION 2-4: CALCULATING THE VOLTAGE ON THE MCP402X DIGITAL

POTENTIOMETER EVALUATION BOARD

R3 Wiper Position RAB()63⁄•()+()

Voltage at Wiper System V

Where:

-----------------------------------------------------------------------------------------

•=

DD

R3 R

AB

R2++

AB

) is

R

DD

R2 R3

AB

=

= = =

5.0V

2.5 kΩ

2.5 kΩ 10 kΩ

System V

The typical step resistance for the 10 kΩ MCP4021 is approximately 158.73Ω. With a 5V supply and a 15 kΩ total resistance (2.5 kΩ + 2.5 kΩ + 10 kΩ), the delta voltage per step is approximately 0.053V.

TABLE 2-3: WIPER POSITION AND CORRESPONDING VOLTAGE

Wiper Wiper Wiper Wiper

Position

(1)

00 01 0.866 17 1.733 33 2.579 49 3.426 02 0.939 18 1.786 34 2.632 50 3.479 03 0.992 19 1.839 35 2.685 51 3.532 04 1.045 20 1.892 36 2.738 52 3.585 05 1.098 21 1.944 37 2.791 53 3.638 06 1.151 22 1.997 38 2.844 54 3.690 07 1.204 23 2.050 39 2.897 55 3.743 08 1.257 24 2.103 40 2.950 56 3.796 09 1.310 25 2.156 41 3.003 57 3.849 10 1.362 26 2.209 42 3.056 58 3.902 11 1.415 27 2.262 43 3.108 59 3.955 12 1.468 28 2.315 44 3.161 60 4.008 13 1.521 29 2.368 45 3.214 61 4.061 14 1.574 30 2.421 46 3.267 62 4.114 15 1.627 31 2.474 47 3.320 63

Note 1: This is zero-scale, wiper is connected to terminal B.

Volta ge

(V)

0.833 16 1.680 32 2.526 48 3.373

2: This is full-scale, wiper is connected to terminal A.

Position

Voltage

(V)

Position

Voltage

(V)

Position

(2)

4.167

Voltage

(V)

2.4 FIRMWARE DESCRIPTION

The 000066_MCP402XEV.ASM source code was written using assembly language for the PIC10F206 microcontroller. Refer to Appendix E. “00066_MCP402XEV.ASM Source Code”. The firmware initializes its I/O so that it can poll the INCR and DECR buttons every millisecond. If the button has been depressed for 40 out of 50 ms, it is considered to be debounced and asserted. The button state is used to determine if a new “Action State” is desired. This simple state machine then decodes the desired action. Once the desired command has been determined, a subroutine that performs the desired command is executed. The low-voltage commands are driven directly from the PIC10F206 I/O, but the high-voltage commands require some additional hardware to generate the required 8V signal.

When a high-voltage command is required, the PIC10F206’s unique OSCOUT feature is utilized. The OSCOUT function allows the instruction clock to be driven on GP2/OSCOUT under software control. A simple charge pump consisting of 2 – 0.01 µF capacitors and a BAV99 dual diode is constructed as seen in Appendix A.2 “Schematic”. When the OSCOUT is enabled, a 1 MHz clock drives the charge pump that produces an 8.4V signal on the MCP401X/2X’s CS V

= 5.0V). Utilizing such a charge pump requires special attention to the timing of the

DD

CS

& U/D signals.

Refer to the comments in the 00066_MCP402XEV.ASM source code for more details on the firmware’s operation. Refer to Appendix E. “00066_MCP402XEV.ASM Source

Code”.

Installation and Operation

pin (assuming

MCP401X/2X Evaluation Board User’s Guide

NOTES:

Appendix A. Schematic and Layouts

A.1 INTRODUCTION

This appendix contains the following schematics and layout diagrams for the MCP402X Digital Potentiometer Evaluation Board.

• Schematic – Shows the schematic of the MCP402X Digital Potentiometer Evaluation Board. The populated PCB was built using this schematic.

• Board Layout – Top Layer + Silk-screen

• Board Layout – Top Silk-Screen

• Board Layout – Bottom Layer + Silk-screen

• Board Layout – Bottom Layer

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

MCP401X/2X Evaluation Board User’s Guide

A.2 SCHEMATIC

M

Schematic and Layouts

A.3 MCP402X BOARD LAYOUT – TOP LAYER + SILK-SCREEN

A.4 MCP402X BOARD LAYOUT – BOTTOM LAYER

MCP401X/2X Evaluation Board User’s Guide

A.5 MCP402X BOARD LAYOUT – TOP SILK-SCREEN

A.6 MCP402X BOARD LAYOUT – BOTTOM LAYER + SILK-SCREEN

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Appendix B. Bill Of Materials (BOM)

TABLE B-1: BILL OF MATERIALS

Qty Reference Description Manufacturer Part Number

2 C1,C2,C3 Cap 0.01 µF 50V CERAMIC

X7R 0805

1 C4 Cap .1 µF 25V CERAMIC

X7R 0805

1 D1 Dual Diode, SOT-23-3,

May substitute with Fairchild

2 INCR, DECR Switch LT Touch 6X3.5

100 GF SMD

1 J1 Conn Header 6pos .100 VERT TIN

(Optional)

1R1 Res 7.5kΩ 1/10W 1%

0805 SMD

2 R2,R3 Res 2.5 kΩ 1/10W 1%

0805 SMD

2 R4,R5 Res 2.5 kΩ 1/10W 1%

0805 SMD

1 U1 MCP4021-103/SN 10 kΩ

Digital Potentiometer

1 U3 PIC10F206, 6-Pin,

8-Bit Flash Microcontrollers

1 U2 MCP4022/23/24 5/6 Pin Digital

Potentiometer (Optional)

7 A,B,W,VDD,GND,

U/D

,CS

Test Point PC Compact SMT (Optional)

®

BAV99

®

Kemet

Panasonic ECG

ON Semiconductor

Panasonic Corporation – ECG

Molex Electronics Corp

Panasonic Corporation – ECG

Microchip Technology Inc. MCP4021-103/SN

Microchip Technology Inc. PIC10F206-I/OT

Microchip Technology Inc. MCP4024-502/OT

Keystone

®

Corporation –

®

/Waldom®

®

Electronics 5016

C0805C103K5RACTU

ECJ-2VB1E104K

BAV99LT1

EVQ-PJS04K

22-28-4061

ERJ-6ENF5111V

MCP401X/2X Evaluation Board User’s Guide

NOTES:

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Appendix C. Using the BFMP Programmer to Power the Board

C.1 POWERING THE BOARD USING THE BFMP PROGRAMMER

The BFMP programmer (PG164101) uses a 6-pin interface for programming. The PICkit™ 2 Flash Starter Kit (PG164120 or DV164120) uses the same interface.

The MCP402X Digital Potentiometer Evaluation Board (MCP402XEV) plugs into the BFMP (or PICkit™ 2 Flash Starter Kit) in the orientation shown in Figure C-1.

USB Cable to PC

BFMP Board

(Top-side)

Pin #1 Pin #1

FIGURE C-1: BFMP Hardware and MCP402X Digital Potentiometer Evaluation Board.

BFMP Header connector

MCP402XEV Board (Bottom-side)

MCP401X/2X Evaluation Board User’s Guide

These programmers use the PICkit™ 1 Baseline Flash Programmer software. This GUI should be configured as shown in Figure C-2. Selecting Device Power causes the BFMP to power the attached board all the time (not just during programming). This allows the MCP402X Digital Potentiometer Evaluation Board to be easily demonstrated without needing to carry a power supply (although a DMM is still required).

Select PIC10F206

FIGURE C-2: PICkit™ 1 Baseline Flash Programmer - Configuration #2.

Note: When programming the MCP402X Digital Potentiometer Evaluation Board,

under

“Board Controls”

the PIC10F206 is only powered during the programming cycle.

Ensure Device Power IS checked and

2.5 kHz Osc is NOT checked.

, DO NOT check Device Power. This ensures that

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Appendix D. Potential Programming Issue of the MCP402XEV

D.1 INTRODUCTION

When programming the MCP402XEV with a Microchip programmer (such as the BPMF or MPLAB ICSPDAT pin. This issue relates to PCBs marked 104-00066 and 104-00066R2.

Due to the current path to ground that is present with the D1 and R1 components through capacitor C2, the programming voltage on the ICSPDAT signal may not meet the voltage requirements of the PIC10F206 GP1 pin.

To address this when programming the board, lift up one of the terminals of capacitor C2 (see Figure D-1). This will stop the ICSPDAT signal voltage from being loaded down while capacitor C2 is charging. The schematic is shown in Figure D-2.

After programming, capacitor C2 must be reconnected to the circuit. This is because this circuit generates the high voltage for the high voltage commands.

®

ICD 2), the PIC10F206 may not program correctly due to the load on the

This capacitor connection needs to be opened for programming.

After programming has been completed, this capacitor needs to be reconnected in the circuit.

lift this end

FIGURE D-1: MCP402XEV R2 PCB Layout – ECN #1.

MCP401X/2X Evaluation Board User’s Guide

M

This is the node that needs to be open when programming.

FIGURE D-2: MCP402XEV R2 Schematic PCB R2, ECN #1.

JP1

C2

MCP401X/2X EVALUATION

BOARD USER’S GUIDE

Appendix E. 00066_MCP402XEV.ASM Source Code

E.1 INTRODUCTION

This appendix documents the example PIC10F20X source code used on the populated PCB. The source code is described in detail by the comments within the.ASM file. The 00066_MCP402XEV.ASM, PIC10F206.INC and MCP402XEV.HEX files can be found on the Microchip web site (www.microchip.com) and on the included CD.

Software License Agreement

The software supplied herewith by Microchip Technology Incorporated (the “Company”) is intended and supplied to you, the Company’s customer, for use solely and exclusively with products manufactured by the Company.

The software is owned by the Company and/or its supplier, and is protected under applicable copyright laws. All rights are reserved. Any use in violation of the foregoing restrictions may subject the user to criminal sanctions under applicable laws, as well as to civil liability for the breach of the terms and conditions of this license.

THIS SOFTWARE IS PROVIDED IN AN “AS IS” CONDITION. NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE

TITLE “MCP402XEV Firmware” ;******************************************************************************************** ; Author: Jim Simons ; Tools: MPLAB(r) 7.10 using MPLINK(tm) ; Editor: ComicSans 8pt w/8 character Tabs ; Files: 00066_MCP402XEV.asm ; p10f206.inc ; ; Description: Exercise the MCP402x devices using the MCP402x EV board. ; Simply use the INCR & DECR buttons to execute the INCR & DECR serial commands. ; ; Serial Commands Action State ; _______________ ______ _____ ; LV Increment w/EE Depress UP, Release UP LVwEE = 1 3 ; LV Decrement w/EE Depress DOWN, Release DOWN LVwEE = 1 4 ; LV Increment w/o EE Depress UP, Release UP LVwEE = x 3 ; LV Decrement w/o EE Depress DOWN, Release DOWN LVwEE = x 4 ; LV 64 Increments Depress UP, Hold for 2s, Release UP 1 ; LV 64 Decrements Depress DOWN, Hold for 2s, Release DOWN 2 ; HV Incr w/o WL Depress UP, Depress DOWN, Release UP, Release DOWN 11 ; HV Decr w/o WL Depress DOWN, Depress UP, Release DOWN, Release UP 12 ; HV 64 Incr w/o WL Depress UP, Depress DOWN, Hold for 2s, Release UP, Release DOWN 5 ; HV 64 Decr w/o WL Depress DOWN, Depress UP, Hold for 2s, Release DOWN, Release UP 6 ; HV Incr w/WL Depress UP, Depress DOWN, Release DOWN, Release UP 13 ; HV Decr w/WL Depress DOWN, Depress UP, Release UP, Release DOWN 14 ;

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

;********************************************************************************************** ; Connections/Schematic ;********************************************************************************************** ; ; MCP pin MCP4021 MCP4022 MCP4023 MCP4024 ; _______ _______ _______ _______ _______ ; 1 Vdd Vdd Vdd Vdd ; 2 Vss Vss Vss Vss ; 3 A U/D U/D U/D ; 4 W CS CS CS ; 5 CS W W W ; 6 B A A ; 7 - - - ; 8 U/D - - ; ; MCP402x PIC10F206 Ext Components ; _______ _________ ______________ ; Vdd Vdd 0.1uF - Vss ; Vss Vss ; A - 2.5k - Vdd ; W - ; B - 2.5k - Vss ; CS GP0/ICSPDAT (int pu) 2.5k - DECR - Vss, 7.5k - CS & BAV99 ; U/D GP1/ICSPCLK (int pu) 2.5k - INCR - Vss ; - GP2/OSCOUT 0.01uF - BAV99 - 0.01uF - Vss ; - GP3/Vpp (int pu) optional SW or Jumper put on BFMP header pins 4 & 6 ; ;********************************************************************************************** ; Assemble Time Variables SaveWiper equ 1 ; comment this line prevent LV commands from Saving the Wiper ; ;********************************************************************************************** ; Configure the PIC ;**********************************************************************************************

list p=10F206 ; list directive to define processor #include <p10F206.inc> ; processor specific variable definitions

__CONFIG _MCLRE_OFF & _CP_OFF & _WDT_ON

ERRORLEVEL -302

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

;********************************************************************************************** ; General Pupose Register Definitions ;********************************************************************************************** GPRS UDATA State res 1 ; variable to track the “state” value ; this code functions as a state machine ; bits 3:0 stores the state 0-15 indicator ; bits 7:6 stores the debounced button states OldState res 1 ; allows program to see if State changed Exit res 1 ; variable to count the number ms to test for a button press DebounceUP res 1 ; variable to count the number of ms UP was pressed DebounceDOWN res 1 ; variable to count the number of ms DOWN was pressed DLYCNT1 res 1 ; variable for the delay subroutines DLYCNT2 res 1 ; variable for the delay subroutines

#define UD GPIO,1 ; GP1 tied to UD & has “INCR” switch connected via 2.2k resistor #define CS GPIO,0 ; GP0 tied to CS & has “DECR” switch connected via 2.2k resistor #define UP GPIO,1 ; Momentary switch UP #define DOWN GPIO,0 ; Momentary switch DOWN #define CP GPIO,2 ; OSCOUT pin for Charge Pump #define PowerDown GPIO,3 ; Vpp for programming & PowerDown input to put uC to SLEEP

#define HV_CS OSCCAL,FOSC4 ; Drives CS to HVDD (drive CS high first)

#define UP_State State,7 ; Debounced UP State - using bits 5:4 are critical #define DOWN_State State,6 ; Debounced DOWN State - using bits 5:4 are critical

;*********************************************************************************************** ; Reset Code ;*********************************************************************************************** RESET CODE ; processor reset vector + 1 ;ResetVector ; Device resets to 0x1FF to get the factory calibration goto Start ; Lower half of memory reserved for subroutines

;*********************************************************************************************** ; Main Code ;*********************************************************************************************** MAIN CODE Start Init_Oscillator ; Internal RC calibration value is placed at location 0xFF by Microchip ; as a movlw k, where the k is a literal value. movwf OSCCAL ; update register with factory cal value ; bcf OSCCAL,FOSC4 ; make sure the FOSC4 is disabled to shut charge pump off

StateMachineReset movlw b’11110011’ ; Disable the Comparator & make inputs digital movwf CMCON0 ; bcf CMCON0, CMPON ; needs to be on to get GP2 as a General Purpose Output movlw b’10011010’ ; disable Wake-Up on Pin Change, ; enable weak pullups for button inputs ; T0CS must be 0 for GP2 TRIS to be active ; set up for 72ms WDT option Init clrf State clrf OldState call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

ButtonCheck ; Debounce Buttons btfss PowerDown ; If pulled low, put uC to SLEEP goto LowPowerMode bsf UP_State bsf DOWN_State ; initialize Button_State to indicate no button pressed movlw .50 ; debounce the buttosns for 50mS to see if pressed movwf Exit movlw .40 ; if pushed for 40 of 50 tests, then valid UP movwf DebounceUP movwf DebounceDOWN DebounceLoop call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .99 call VAR5TcyDELAY ; 5 + (99*5) = 500us btfss UP decfsz DebounceUP,f goto CheckDOWN bcf UP_State ; UP Button Pressed CheckDOWN call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .99 call VAR5TcyDELAY ; 5 + (99*5) = 500us btfss DOWN decfsz DebounceDOWN,f goto DebounceLoopTest bcf DOWN_State ; DOWN Button Pressed DebounceLoopTest decfsz Exit,f goto DebounceLoop

call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movf State,w call DetermineState ; subroutine to determine the next state movwf State xorwf OldState,w btfss STATUS,Z call PerformState ;State changed, now do something movlw .5 call VAR1000TcyDELAY ; Make sure EE Write Cycle has finished movf State,w movwf OldState goto ButtonCheck ; Loop for button presses

;*********************************************************************************************** ; State Machine Code ;*********************************************************************************************** State0 goto StateMachineReset ; State 0, no action, shouldn’t get here

State1 ; UP button pressed movlw .200 ; 200x10mS = 2s movwf Exit

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

Loop1_2sec call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfss DOWN ; if DOWN gets pressed, exit retlw .1 call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfsc UP ; if UP gets released, exit retlw .1 decfsz Exit,f goto Loop1_2sec call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .64 call LV_Increment ; movlw .4 ; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) LV_IncrExit clrwdt btfss UP ; if UP gets released, exit goto LV_IncrExit clrf State retlw .1 State2 ; DOWN button pressed movlw .200 ; 200x10mS = 2s movwf Exit Loop2_2sec call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfss UP ; if UP gets pressed, exit retlw .2 call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfsc DOWN ; if DOWN gets released, exit retlw .2 decfsz Exit,f goto Loop2_2sec call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands undesired U/D commands movlw .64 call LV_Decrement ; movlw .4 ; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) LV_DecrExit clrwdt btfss DOWN ; if DOWN gets released, exit goto LV_DecrExit clrf State retlw .2 State3 ; LV Increment call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .1 call LV_Increment clrf State retlw .3

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

State4 ; LV Decrement call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .1 call LV_Decrement clrf State retlw .4 State5 ; Both buttons pressed movlw .200 ; 200x10mS = 2s movwf Exit Loop5_2sec call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfsc UP ; if UP gets released, exit retlw .5 call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfsc DOWN ; if DOWN gets released, exit retlw .5 decfsz Exit,f goto Loop5_2sec call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .64 call HV_Increment_WL_Disable ; movlw .4 ; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle HV_IncrExit clrwdt call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .10 call VAR1000TcyDELAY ; add a 10mS delay for settling time btfss DOWN ; if DOWN gets released, exit goto HV_IncrExit call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .10 call VAR1000TcyDELAY ; add a 10mS delay for settling time btfss UP ; if UP gets released, exit goto HV_IncrExit clrf State retlw .5 State6 movlw .200 ; 200x10mS = 2s movwf Exit Loop6_2sec call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfsc UP ; if UP gets released, exit retlw .6 call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .5 ; 5ms delay call VAR1000TcyDELAY btfsc DOWN ; if DOWN gets released, exit retlw .6 decfsz Exit,f goto Loop6_2sec call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .64 call HV_Decrement_WL_Disable ; movlw .4 ; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

HV_DecrExit clrwdt call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled) movlw .10 call VAR1000TcyDELAY ; add a 10mS delay for settling time btfss UP ; if UP gets released, exit goto HV_DecrExit call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled) movlw .10 call VAR1000TcyDELAY ; add a 10mS delay for settling time btfss DOWN ; if DOWN gets released, exit goto HV_DecrExit clrf State retlw .6 State7 State8 State9 State10 State11 ; HV Increment w/o WL call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .1 call HV_Increment_WL_Disable clrf State retlw .11 State12 ; HV Increment w/o WL call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands movlw .1 call HV_Decrement_WL_Disable clrf State retlw .12 State13 ; HV Decrement w/WL call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands call HV_Increment_WL_Enable clrf State retlw .13 State14 ; HV Decrement w/WL call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands call HV_Decrement_WL_Enable clrf State retlw .14 State15 goto StateMachineReset

;*********************************************************************************************** ; Low Power Mode ;*********************************************************************************************** LowPowerMode movlw b’11111000’ ; make all I/O pins an output tris GPIO movlw b’11111111’ movwf GPIO ; output high movlw b’10011111’ ; disable Wake-Up on Pin Change, ; enable weak pullups for button inputs ; T0CS must be 0 for GP2 TRIS to be active ; set up for 2.3ms WDT option sleep ; put into lowest power setting goto Start ; shouldn’t get here

SUBS CODE

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

;*********************************************************************************************** ; State Machine Subroutines ;*********************************************************************************************** DetermineState swapf State,f rrf State,f rrf State,w andlw b’00111111’ ; mask invalid states addwf PCL,f S0_00 retlw .0 ; both buttons pressed at same time, shouldn’t be here S0_01 retlw .1 ; UP button pressed, change state S0_10 retlw .2 ; DOWN button pressed, change state S0_11 retlw .0 ; no change S1_00 retlw .5 ; both buttons pressed, change state S1_01 retlw .1 ; no change S1_10 retlw .0 ; shouldn’t be here, reset state S1_11 retlw .3 ; UP button released, change state S2_00 retlw .6 ; both buttons pressed, change state S2_01 retlw .0 ; shouldn’t be here, reset state S2_10 retlw .2 ; no change S2_11 retlw .4 ; DOWN button released, change state S3_00 retlw .0 ; shouldn’t be here, reset state S3_01 retlw .0 ; shouldn’t be here, reset state S3_10 retlw .0 ; shouldn’t be here, reset state S3_11 retlw .0 ; shouldn’t be here, reset state S4_00 retlw .0 ; shouldn’t be here, reset state S4_01 retlw .0 ; shouldn’t be here, reset state S4_10 retlw .0 ; shouldn’t be here, reset state S4_11 retlw .0 ; shouldn’t be here, reset state S5_00 retlw .5 ; no change S5_01 retlw .7 ; DOWN button released, change state S5_10 retlw .9 ; UP button released, change state S5_11 retlw .0 ; shouldn’t be here, reset state S6_00 retlw .6 ; no change S6_01 retlw .10 ; DOWN button released S6_10 retlw .8 ; UP button released S6_11 retlw .0 ; shouldn’t be here, reset state S7_00 retlw .5 ; both buttons pressed again, change state S7_01 retlw .7 ; no change S7_10 retlw .0 ; shouldn’t be here, reset state S7_11 retlw .13 ; UP button released, change state S8_00 retlw .6 ; both buttons pressed again, change state S8_01 retlw .0 ; shouldn’t be here, reset state S8_10 retlw .8 ; no change S8_11 retlw .14 ; DOWN button released, change state S9_00 retlw .5 ; both buttons pressed again, change state S9_01 retlw .0 ; shouldn’t be here, reset state S9_10 retlw .9 ; no change S9_11 retlw .11 ; DOWN button released, change state S10_00 retlw .6 ; both buttons pressed again, change state S10_01 retlw .10 ; no change S10_10 retlw .0 ; shouldn’t be here, reset state S10_11 retlw .12 ; DOWN button released, change state S11_00 retlw .0 ; shouldn’t be here, reset state S11_01 retlw .0 ; shouldn’t be here, reset state S11_10 retlw .0 ; shouldn’t be here, reset state S11_11 retlw .0 ; shouldn’t be here, reset state S12_00 retlw .0 ; shouldn’t be here, reset state S12_01 retlw .0 ; shouldn’t be here, reset state S12_10 retlw .0 ; shouldn’t be here, reset state S12_11 retlw .0 ; shouldn’t be here, reset state S13_00 retlw .0 ; shouldn’t be here, reset state S13_01 retlw .0 ; shouldn’t be here, reset state

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

S13_10 retlw .0 ; shouldn’t be here, reset state S13_11 retlw .0 ; shouldn’t be here, reset state S14_00 retlw .0 ; shouldn’t be here, reset state S14_01 retlw .0 ; shouldn’t be here, reset state S14_10 retlw .0 ; shouldn’t be here, reset state S14_11 retlw .0 ; shouldn’t be here, reset state S15_00 retlw .0 ; shouldn’t be here, reset state S15_01 retlw .0 ; shouldn’t be here, reset state S15_10 retlw .0 ; shouldn’t be here, reset state S15_11 retlw .0 ; shouldn’t be here, reset state

PerformState movf State,w andlw b’00001111’ ; mask all states >15 addwf PCL,f ; jump to desired State retlw .0 ; State 0, no action goto State1 ; (2s for repeating LV increment) goto State2 ; (2s for repeating LV decrement) goto State3 goto State4 goto State5 ; (2s for repeating HV increment) goto State6 ; (2s for repeating HV decrement) retlw .7 ; State 7, no action retlw .8 ; State 8, no action retlw .9 ; State 9, no action retlw .10 ; State 10, no action goto State11 goto State12 goto State13 goto State14 goto StateMachineReset ; State 15... shouldn’t be here

;*********************************************************************************************** InitGPIO movlw b’00001011’ ; initialize UP and DOWN switches to be high & CP to be low. movwf GPIO movlw b’11111100’ ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands tris GPIO retlw b’11000000’ GPIO_TestUP movlw b’00001011’ ; initialize UP and DOWN switches to be high & CP to be low. movwf GPIO movlw b’11111100’ ; make both GP0/DECR/CS & GP1/INCR/UD outputs, prevent undesired U/D commands tris GPIO movlw b’11111110’ ; make GP1/INCR/UD an input (w/pu enabled) tris GPIO retlw b’10000000’ GPIO_TestDOWN movlw b’00001011’ ; initialize UP and DOWN switches to be high & CP to be low. movwf GPIO movlw b’11111100’ ; make both GP0/DECR/CS & GP1/INCR/UD outputs, prevent undesired U/D commands tris GPIO movlw b’11111101’ ; make GP0/DECR/CS an input (w/pu enabled) tris GPIO retlw b’01000000’

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

;*********************************************************************************************** ; Button Isolation Subroutines ;*********************************************************************************************** ; Low Voltage Increment & Decrement Subroutines ;*********************************************************************************************** LV_Increment movwf Exit ; load the loop counter bsf UD goto $+1 ; creates a 3us total delay bcf CS movlw .100 ; 5*100 = 500us delay to pull down CS movwf DLYCNT1 DLOOP_LVI clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_LVI LV_IncrLoop bcf UD goto $+1 bsf UD goto $+1 ; creates a 3us total delay decfsz Exit,f ; Have we incremented the wiper enough? goto LV_IncrLoop IFDEF SaveWiper bcf UD goto $+1 ; creates a 3us total delay ENDIF bsf CS retlw 0x00 ; Follow w/long delay to ramp CS & EEPROM Write Cycle

LV_Decrement movwf Exit ; load the loop counter bcf UD goto $+1 ; creates a 3us total delay bcf CS movlw .100 ; 5*100 = 500us delay to pull down CS movwf DLYCNT1 DLOOP_LVD clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_LVD IFDEF SaveWiper goto LV_DecrLoop+4 ; skip first Decrement since final edge is rising ENDIF LV_DecrLoop bsf UD goto $+1 ; creates a 3us total delay bcf UD goto $+1 ; creates a 3us total delay decfsz Exit,f ; Have we decremented the wiper enough? goto LV_DecrLoop IFDEF SaveWiper bsf UD goto $+1 ; creates a 3us total delay ENDIF bsf CS ; Follow w/long delay to ramp CS & EEPROM Write Cycle retlw 0x01

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

;*********************************************************************************************** ; High Voltage Increment & Decrement Subroutines ;*********************************************************************************************** HV_Increment_WL_Disable movwf Exit ; load the loop counter bsf UD goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time movwf DLYCNT1 DLOOP_HVI clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_HVI HV_IncrLoop bcf UD goto $+1 ; creates a 3us total delay bsf UD goto $+1 ; creates a 3us total delay decfsz Exit,f ; Have we incremented the wiper enough? goto HV_IncrLoop bcf HV_CS ; shut off 1Mhz Charge Pump bcf CS ; helps pull the signal down from HV goto $+1 bsf CS retlw 0x02 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

HV_Decrement_WL_Disable movwf Exit ; load the loop counter bcf UD goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time movwf DLYCNT1 DLOOP_HVD clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_HVD HV_DecrLoop bsf UD goto $+1 ; creates a 3us total delay bcf UD goto $+1 ; creates a 3us total delay decfsz Exit,f ; Have we decremented the wiper enough? goto HV_DecrLoop bcf HV_CS ; shut off 1Mhz Charge Pump bcf CS ; helps pull the signal down from HV goto $+1 bsf CS retlw 0x03 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

HV_Increment_WL_Enable bsf UD goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time movwf DLYCNT1

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

DLOOP_HVIWL clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_HVIWL bcf UD goto $+1 ; creates a 3us total delay bsf UD goto $+1 ; creates a 3us total delay bcf UD goto $+1 ; creates a 3us total delay bcf HV_CS ; shut off 1Mhz Charge Pump bcf CS ; helps pull the signal down from HV goto $+1 bsf CS retlw 0x04 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

HV_Decrement_WL_Enable bcf UD bsf CS goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time movwf DLYCNT1 DLOOP_HVDWL clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_HVDWL bsf UD goto $+1 ; creates a 3us total delay bcf HV_CS ; shut off 1Mhz Charge Pump bcf CS ; helps pull the signal down from HV goto $+1 bsf CS retlw 0x05 ; Follow w/long delay to discharge pump & EEPROM Write Cycle ;*********************************************************************************************** ; VARIABLE DELAY SUBROUTINES ;*********************************************************************************************** ; DLYCNT1 = F9h = 249d DLYCNT2 = W ; DELAY = T((4 DLYCNT1 + 4) DLYCNT2 + 4) ; ; ex. To create a 300ms delay when using a 4Mhz osc, 300-250 = 50 ; movlw .50 ;load .50 into WREG ; call VAR1000TcyDELAY ;call VAR1000TcyDELAY = 50ms delay w/4MHz Osc ; call VAR1000TcyDELAY ;call VAR1000TcyDELAY = 250ms delay w/4MHz Osc ; ;total = 300ms delay ;************ ; The value in W at the time of the CALL = x. Delay = 1000Tcy*x VAR1000TcyDELAY movwf DLYCNT2 ; LOADS CONTROLLING DLY # INTO PRIMARY COUNTER DLOOP2 movlw .249 ; MAXIMIZES THE SECONDARY DLY COUNTER movwf DLYCNT1 DLOOP1 clrwdt ;or NOP decfsz DLYCNT1,f ; DECREMENT AND TEST SECONDARY LOOP FOR ZERO goto DLOOP1 ; CONTINUE SECONDARY LOOP decfsz DLYCNT2,f ; DECREMENT AND TEST PRIMARY DLY COUNTER goto DLOOP2 ; CONTINUE PRIMARY LOOP retlw .250 ; preload W for the next CALL VAR1000TcyDELAY

00066_MCP402XEV.ASM Source Code

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)

;************ ; VARIABLE 5 Tcy DELAY UP TO 256*5Tcy+5Tcy ; DLYCNT1 = W ; DELAY = T(1 + 5 DLYCNT1 - 1) + CALL + RETLW ; ; ex. To create a 250us delay, (250/5)-1 = 49 ; movlw .49 ;load .49 into WREG ; call VAR5TcyDELAY ;call VAR5TcyDELAY ;************ ; The value in W at the time of the CALL = x. Delay = 5*Tcy + 5Tcy VAR5TcyDELAY movwf DLYCNT1 ; LOADS CONTROLLING DLY # INTO PRIMARY COUNTER DLOOP3 clrwdt ;or NOP nop decfsz DLYCNT1,f ; DECREMENT AND TEST ZERO goto DLOOP3 ; CONTINUE LOOP retlw .250 ; preload W for the next CALL VAR5TcyDELAY ;***********************************************************************************************

end

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10/31/05

Microchip Technology MCP401X, MCP402X User’s Guide

Specifications and Main Features

Frequently Asked Questions

User Manual

INTRODUCTION

DOCUMENT LAYOUT

CONVENTIONS USED IN THIS GUIDE

RECOMMENDED READING

THE MICROCHIP WEB SITE

CUSTOMER SUPPORT

DOCUMENT REVISION HISTORY

1.1 INTRODUCTION

1.2 WHAT IS THE MCP402X DIGITAL POTENTIOMETER EVALUATION BOARD?

2.1 INTRODUCTION

2.2 PCB DESCRIPTION

2.3 TEST AND OPERATING INSTRUCTIONS

2.4 FIRMWARE DESCRIPTION

Appendix A. Schematic and Layouts

A.1 INTRODUCTION

Appendix B. Bill Of Materials (BOM)

Appendix C. Using the BFMP Programmer to Power the Board

C.1 POWERING THE BOARD USING THE BFMP PROGRAMMER

Appendix D. Potential Programming Issue of the MCP402XEV

D.1 INTRODUCTION

Appendix E. 00066_MCP402XEV.ASM Source Code

E.1 INTRODUCTION

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