Digilent 410-297P User Manual

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ChipKIT MX3 Board Reference Manual

Revised November 7, 2013 This manual applies to the ChipKIT MX3 REV ?

Table of Contents

Table of Contents .................................................................................................................. 1

Overview ............................................................................................................................... 3

Specifications .......................................................................................................................... 3

1 Programming Tools ........................................................................................................ 3

1.1 Using the ChipKIT MX3 with the MPIDE ........................................................................... 4

1.2 Using the ChipKIT MX3 with Microchip Development Tools ........................................... 5

1.3 Additional Reference Documentation ............................................................................. 6

2 Power Supply ................................................................................................................. 6

2.1 RESET Pmod™ ................................................................................................................... 7

3 Pmod™ Connectors ........................................................................................................ 7

4 Digital Inputs and Outputs ............................................................................................. 9

4.1 User LEDs ........................................................................................................................ 10

4.2 5V Signal Compatibility .................................................................................................. 10

5 CPU Clock Source ......................................................................................................... 10

6 UART Interface ............................................................................................................. 11

7 Serial Peripheral Interface (SPI) .................................................................................... 12

8 I2C™ Interface .............................................................................................................. 13

DOC#: 502-297

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ChipKIT MX3 Board Reference Manual

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9 Analog Inputs ............................................................................................................... 14

10 A/D Converter Reference ............................................................................................. 15

11 Timers ......................................................................................................................... 15

12 Output Compare .......................................................................................................... 16

13 Input Capture ............................................................................................................... 16

14 External Interrupts ....................................................................................................... 17

15 RTCC ............................................................................................................................ 17

Appendix A: Connector Description and Jumper Settings ..................................................... 18

Appendix B: Example of Configuration Values ...................................................................... 19

Appendix C: Connector Pinout Tables .................................................................................. 20

Arranged by Microcontroller Pin Number ................................................................................ 20

Arranged by Connector Pin Number and Digital Pin Number .................................................. 22

Arranged by Microcontroller I/O Port Name and Bit Number ................................................. 24

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ChipKIT MX3 Board Reference Manual

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Overview

ChipKIT MX3 is the new name for Cerebot MX3. This board retains all functionality of the Cerebot MX3.

The ChipKIT MX3 is a microcontroller development board based on the Microchip PIC32MX320F128H, a member of the 32-bit PIC32 microcontroller family. It is compatible with Digilent’s line of Pmod™ peripheral modules, and is suitable for use with the Microchip MPLAB® IDE tools. The ChipKIT MX3 is also compatible for use with the chipKIT™ MPIDE development environment. ChipKIT MPIDE is a PIC32 based system compatible with many existing Arduino™ code examples, reference materials, and other resources.

Specifications

• Microcontroller: PIC32MX320F128H

• Flash Memory: 128K

• RAM Memory: 16K

• Operating Voltage: 3.3V

• Max Operating Frequency: 80Mhz

• Typical operating current: 75mA

• Input Voltage (recommended): 7V to 15V

• Input Voltage (maximum): 20V

• I/O Pins: 42 total

• Analog Inputs: 12

• Analog input voltage range: 0V to 3.3V

• DC Current per pin: +/-18mA

The ChipKIT MX3

The ChipKIT MX3 is designed to be easy to use and suitable for use by anyone from beginners to advanced users for experimenting with electronics and embedded control systems. It is intended to be used with either the MultiPlatform IDE, (modified Arduino IDE), MPIDE, or the Microchip MPLAB IDE. The kit contains everything needed to start developing embedded applications using the MPIDE. In order to use the MPLAB IDE, an additional programming/debugging device, such as a Microchip PICkit3 is required.

The ChipKIT MX3 provides 42 I/O pins that support a number of peripheral functions, such as UART, SPI, and I2C™ ports, as well as five pulse width modulated outputs and five external interrupt inputs. Eleven of the I/O pins can be used as analog inputs in addition to their use as digital inputs and outputs.

The ChipKIT MX3 can be powered via USB, an external power supply that may be either an AC-DC power adapter, or batteries.

1 Programming Tools

The ChipKIT MX3 is designed to be used with either the Multi-Platform IDE (MPIDE), the development software environment used with the chipKIT™ system, or as a more traditional microcontroller development platform using the Microchip MPLAB® IDE and development tools. The ChipKIT MX3 if fully compatible with Microchip development tools that support the PIC32 family of microcontrollers.

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ChipKIT MX3 Board Reference Manual

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The ChipKIT MX3 is immediately useable with the MPIDE. Additional hardware is required to use the Microchip MPLAB tools.

1.1 Using the ChipKIT MX3 with the MPIDE

ChipKIT and the MPIDE is a PIC32 based hardware and software system compatible with many existing Arduino™ code examples, reference materials, and other resources. The MPIDE development platform was produced by modifying the Arduino™ IDE and is fully backward compatible with the Arduino IDE. The ChipKIT MX3 board is designed to be fully compatible with the MPIDE system, version 20111209 or later.

The MPIDE uses a serial communications port to communicate with a boot loader running in the target board. The serial port on the MX3 board is implemented using an FTDI FT232R USB serial converter. Before attempting to use the MPIDE to communicate with the MX3, the appropriate USB device driver must be installed.

The ChipKIT MX3 board uses a standard mini-USB connector for connection to a USB port on the PC. Use a standard USB-A to mini-B cable (not provided) to connect the board to an available USB port on the PC.

In the MPIDE, use the “Tools.Board” command to select the ChipKIT MX3 from the list of available boards. Use the “Tools.Serial Port” command to choose the appropriate serial port from the list of available serial ports on the PC.

When the MPIDE needs to communicate with the MX3 board, the board is reset and starts running the boot loader. The MPIDE then establishes communications with the boot loader and downloads the program to the board.

When the MPIDE opens the serial communications connection on the PC, the DTR pin on the FT232R chip is driven low. This pin is coupled through a capacitor to the MCLR pin on the PIC32 microcontroller. Driving the MCLR line low resets the microcontroller, restarting execution with the boot loader.

Once the MPIDE has established communication with the boot loader, it transfers the user’s program to the boot loader, which programs it into the flash memory in the Microcontroller.

The automatic reset action when the serial communications connection is opened can be disabled. To disable this operation, remove the shorting block from jumper JP1. It is also possible that it will interfere with the operation of the MPLAB IDE and a Microchip hardware programmer/debugger. In this case, the shorting block should also be removed from JP1. The shorting block is reinstalled on JP1 to restore operation with the MPIDE.

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ChipKIT MX3 Board Reference Manual

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Two red LEDs (LD1 and LD2) will blink when data is being sent or received between the ChipKIT MX3 and the PC over the serial connection.

The header connector J3 provides access to the other serial handshaking signals provided by the FT232R. Connector J3 is not loaded at the factory but can be installed by the user to access these signals.

1.2 Using the ChipKIT MX3 with Microchip Development Tools

In addition to being used with the MPIDE, the ChipKIT MX3 can be used as a more traditional microcontroller development board using Microchip Development Tools.

The Microchip MPLAB® IDE or the MPLAB® X IDE can be used to program and debug code running on the ChipKIT MX3 board. These programs can be downloaded from the Microchip web site. These software suites include a free evaluation copy of the Microchip C32 compiler for use with the PIC32 microcontroller family.

When creating a new project, use the “Configure.Select Device…” menu to specify the PIC32 device being used. Ensure that the device is set to PIC32MX320F128H.

Programming and debugging a program on the ChipKIT MX3 using the MPLAB IDE requires the use of external programming hardware. Typically, this will be a Microchip PICkit™3, but can be any other tool that supports the same connection interface as the PICkit3 and supports the PIC32MX3XX processor family.

Connector JP3 on the left side of the board is used to connect to the Microchip hardware development tool. This connector is not loaded at the factory, but can be installed by the user if desired. The holes for JP3 are staggered so that a standard, 100mil spaced, 6-pin header can be press fit to the board without the need to solder it in place. The connector at JP3 can be soldered in place if desired for a more reliable permanent connection.

Typically, a right angle male connector will be used in JP3 so that a PICkit3 can be attached coplanar with the ChipKIT MX3 board. If the connector is loaded from the top, the PICkit3 will be upright (button and LEDs visible). Alternatively, the connector can be loaded from the bottom. In this case, the PICkit3 will be upside down.

If JP3 is loaded from the top, the PICkit3 will interfere with the USB connector and the external power connector. A short six-wire cable can be used between the PICkit3 and the ChipKIT MX3. If JP3 is loaded from the bottom, the PICkit3 will not interfere with the USB and external power connectors.

Digilent has a kit available (PICkit3 Programming Cable Kit) that includes all necessary connectors and the cable for connecting a PICkit3 to the ChipKIT MX3.

The MCLR pin on the PIC32 microcontroller is used by the hardware programming/debugging interface to reset the processor. This same pin is used by the USB serial converter to reset the processor when using the MPIDE. It is possible that the reset function from the USB serial interface can interfere with correct operation of the Microchip programming and debugging tools. If this happens, jumper JP1 can be used to disconnect the USB serial converter reset circuit. Remove the shorting block from JP1 to disable the reset circuit. If the shorting block has been removed, it is necessary to reinstall it on JP1 in order to use the ChipKIT MX3 board with the MPIDE again.

Using the Microchip development tools to program the ChipKIT MX3 will erase the boot loader. To use the board with the MPIDE again, it is necessary to program the boot loader back onto the board. The programming file for the boot loader programmed into the board by Digilent at the factory is available for download from the product page for the ChipKIT MX3 on the Digilent web site. Additionally, the boot loader source code is available in the chipKIT project repository at www.github.com/chipKIT32/pic32-Arduino-Bootloader.

To reprogram the boot loader using MPLAB, perform the following steps:

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ChipKIT MX3 Board Reference Manual

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• Use the “Configure.Select Device …” menu to select the PIC32MX320F128H

• Use the “Programmer.Select Programmer” menu to select the “PICkit3” or other hardware programming tool

being used.

• Use the “File Import…” dialog box to navigate to and select the boot loader programming downloaded from the Digilent web site. The file name will be something like: chipKIT_Bootloader_MX3.hex

• Use the “Programmer.Program” command to program all memories on the device.

1.3 Additional Reference Documentation

For additional information about the ChipKIT MX3 board and the use and operation of the PIC32MX320F128H microcontroller, refer to the following documents in addition to this reference manual.

The ChipKIT MX3 Schematic, available on the ChipKIT MX3 product page on the Digilent web site:

www.digilentinc.com

The PIC32MX3XX/4XX Family Data Sheet and the PIC32MX Family Reference Manual available from the Microchip web site: www.microchip.com

Additional reference material for the MPIDE system is included in the MPIDE software download, and on-line in the chipKIT wiki. Help with questions and problems using the board with the MPIDE software can also be obtained in the chipKIT forums:

www.chipKIT.net/install (software download) www.chipKIT.net www.chipKIT.org/forum

2 Power Supply

The ChipKIT MX3 is designed to be powered either from USB or from an external power supply. There is an automatic switchover circuit that causes the external supply to be used if both supplies are present.

The power supply section uses two voltage regulators. The first regulates the external voltage to 5V to power the VCC5V0 bus. The second regulates the VCC5V0 bus to 3.3V to provide power to the VCC3V3 bus that powers the PIC32 microcontroller.

The 5V voltage regulator, IC2, is normally an NCP1117. The board is designed to be able to also use an LM1117, but the NCP1117 is the part normally used. The NCP1117 is rated for an output current of 1A (the LM1117 is rated for 800mA). The dropout voltage of the NCP1117 is a maximum of 1.2V at the rated output current (1.3V for the LM1117). There is a reverse polarity protection diode in the external power supply circuit. Considering the diode drop plus the forward drop across the regulator, the minimum input voltage to the regulator should be 7V to produce a reliable 5V output. The absolute maximum input voltage of both the NCP1117 and the LM1117 is 20V. The recommended maximum operating voltage is 15V. For input voltages above 9V, the regulator will get extremely hot when drawing high currents. Both the NCP1117 and the LM1117 have output short circuit protection and internal thermal protection and will shut down automatically to prevent damage.

The 3.3V regulator, IC3, is a Microchip MCP1725. This regulator is rated for a maximum output current of 500mA. The absolute maximum input voltage for the MCP1725 is 6V. This regulator has internal short circuit protection and thermal protection. It will get noticeably warm when the current consumed by the VCC3V3 bus is close to the 500mA maximum.

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ChipKIT MX3 Board Reference Manual

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The 5V power bus, VCC5V0 can be powered from one of three sources: 1) The USB5V0 bus when the board is operating under USB power; 2) The output of the on-board 5V regulator when operating from an external 7V–15V supply; or 3) Directly from the external supply when operating from a regulated 5V external supply and jumper JP2 is in the BYP position.

Switchover from USB power to external power is done automatically and the external supply will be used if both are present.

Jumper JP2 is used to route the external power supply voltage through the on-board 5V regulator or directly to the VCC5V0 bus, bypassing the on-board 5V regulator. Normally, JP2 should be in the REG position. This routes the external supply through the 5V regulator. Operation from an externally regulated 5V supply is accomplished by placing the jumper in the BYP position.

The forward drop across the MCP1725 is typically 210mV (350mV max) at 500mA output. With JP2 in the BYP position, this will allow correct operation of the 3.3V power supply from an input voltage down to 3.5V. This allows powering the board from batteries and other lower voltage power sources. In this case, the VCC5V0 power bus will not be powered at 5V.

NOTE: It is extremely important to observe the MCP1725 maximum input voltage rating of 6V when JP2 is in the BYP position. Applying more than 6V to the external power input with the jumper in the BYP position can damage the 3.3V regulator and possibly the PIC32 microcontroller as well.

The PIC32 microcontroller is rated to use a maximum of 75mA of current when operating at 80 MHz. This allows up to 425mA from the VCC3V3 bus and up to 925mA from the VCC5V0 bus to power external devices. The combined power used by the VCC5V0 bus and the VCC3V3 bus should not exceed 925mA.

The ChipKIT MX3 can provide power to any peripheral modules attached to the Pmod connectors, JA-JE, and to I2C devices connected to the I2C daisy chain connector,

J2. Each Pmod connector provides power pins that can be powered from either the switched main power bus, VCC5V0, or the regulated voltage, VCC3V3, by setting the voltage jumper block to the desired position.

The I2C power connector only provides 3.3V from the VCC3V3 bus.

It is also possible to power the ChipKIT MX3 from any one of the Pmod connectors or the I2C connector. When powering the board from a Pmod connector with the power select jumper in the 5V0 position, a voltage applied at the Pmod connector will power the VCC5V0 bus and be regulated to 3.3V for the VCC3V3 bus. When powering the board from the I2C connector or a Pmod connector with the power select jumper in the 3V3 position, only the VCC3V3 bus will be powered and the VCC5V0 bus will not be powered.

2.1 RESET

A reset button is at the upper left corner of the board. Pressing this button will reset the PIC32 microcontroller.

3 Pmod™ Connectors

The ChipKIT MX3 has five connectors for connecting Digilent Pmod peripheral modules. The Pmod connectors, labeled JA–JF, are 2x8 right-angle, female pin header connectors. Each connector has an associated power select jumper block labeled JPA–JPF.

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ChipKIT MX3 Board Reference Manual

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Digilent Pmods are a line of small peripheral modules that provide various kinds of I/O interfaces. The Pmod product line includes such things as button, switch and LED modules, connector modules, LCD displays, high current output drivers, and many others.

There are two styles of Pmod connector: six-pin and twelve-pin. Both connectors use standard pin headers with 100mil spaced pins. The six-pin connectors have the pins in a 1x6 configuration, while the twelve-pin connectors use a 2x6 configuration. All of the Pmod connectors on the ChipKIT MX3 are twelve pin connectors.

The six-pin connectors provide four I/O signals, ground and a switchable power connection. The twelve-pin connectors provide eight I/O signals, two power and two ground pins. The twelve-pin connectors have the signals arranged so that one twelve-pin connector is equivalent to two of the six-pin connectors. Pins 1–4 and 7–10 are the signal pins, pins 5 and 11 are the ground pins and pins 6 & 12 are the power supply pins.

The pin numbering that Digilent uses on the twelve-pin Pmod connectors is non-standard. The upper row of pins are numbered 1–6, left to right (when viewed from the top of the board), and the lower row of pins are numbered 7–12, left to right. This is in keeping with the convention that the upper and lower rows of pins can be considered to be two six-pin connectors stacked. When viewed from the end of the connector, pin 1 is the upper right pin and pin 7 is immediately below it (closer to the PCB).

Each Pmod connector has an associated power select jumper. These are used to select the power supply voltage supplied to the power supply pin on the Pmod connector. They are switchable between either the regulated 5V power supply or the 3.3V main board supply. Place the shorting block in the 3V3 position for regulated 3.3V and in the 5V0 position for regulated 5V. Note that the 5V0 position will supply the unregulated input supply if the regulator bypass jumper JP2 is in the BYP position.

Each signal pin on the Pmod connectors is connected to an input/output pin on the PIC32 microcontroller. Each pin has a 200 ohm series resistor and an ESD protection diode. The series resistor provides short circuit protection to prevent damaging the I/O block in the microcontroller if the pin is inadvertently shorted to VDD or GND, or two outputs are shorted together. The ESD protection diode protects the I/O block from damage due to electro-static discharge.

Although ESD protection is provided between the connector pins and the microcontroller pins, ESD safe handling procedures should be followed when handling the circuit board. The pins on the microcontroller and other circuits on the board are exposed and can be damaged through ESD when handling the board.

Digilent Pmod peripheral modules can either be plugged directly into the connectors on the ChipKIT MX3 or attached via cables. Digilent has a variety of Pmod interconnect cables available.

See the Pinout Tables in Appendices B–D below for more information about connecting peripheral modules and other devices to the ChipKIT MX3. These tables indicate the mapping between pins on the PIC32MX320 microcontroller and the pins on the various connectors.

The PIC32 microcontroller can source or sink a maximum of 18mA on all digital I/O pins. However, to keep the output voltage within the specified input/output voltage range (VOL 0.4V, VOH 2.4V) the pin current must be restricted to +7/-12mA. The maximum current that can be sourced or sunk across all I/O pins simultaneously is +/200mA. The maximum voltage that can be applied to any digital I/O pin is 5.5V. For more detailed specifications, refer to the PIC32MX3XX/4XX Data Sheet.

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