CE219490 – PSoC 6 MCU Ramping LED
using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 1
Objective
This example demonstrates the flexibility of Smart I/O in PSoC® 6 MCU, by implementing an LED ramping effect exclusively in
hardware with no CPU usage beyond initialization.
Requirements
Tool: ModusToolbox™ IDE 1.1
Programming Language: C
Associated Parts: All PSoC 6 MCU parts
Related Hardware: PSoC 6 BLE Pioneer Kit, PSoC 6 WiFi-BT Pioneer Kit, PSoC6 WiFi-Prototyping Kit
Overview
This example uses a PWM resource and Smart I/O in PSoC 6 MCU to implement a ramping LED, where an LED gradually
cycles through increasing and decreasing brightness levels. There is no CPU usage except for the initialization of PWM and
Smart I/O.
Hardware Setup
This example uses the kit’s default configuration. See the kit guide to ensure the kit is configured correctly.
Note: The PSoC 6 BLE Pioneer kit and the PSoC 6 WiFi-BT Pioneer kit ship with KitProg2. ModusToolbox only works with
KitProg3. Before using this code example, make sure that the kit is upgraded to KitProg3. See ModusToolbox Help >
ModusToolbox IDE Documentation > User Guide; section PSoC 6 MCU KitProg Firmware Loader. If you do not upgrade, you
will see an error like “unable to find CMSIS-DAP device” or “KitProg firmware is out of date”.
Software Setup
None.
Operation
Follow the instructions that came with your kit to make sure that your kit is connected to your PC
1. Connect the kit to your PC using the provided USB cable.
2. Import the application into a new workspace. See KBA225201.
3. Build the application. Choose Project > Build All.
4. Program the PSoC 6 MCU device. In the project explorer, select the mainapp project. In the Quick Panel, scroll to the
Launches section and click the Program (KitProg3) configuration. Program configurations also build the code.
5. Using a jumper wire, connect P9[4] to P13[7].
You can observe the ramping effect on the LED connected to P13[7] on the kit.
Debugging
You can debug the example to step through the code. Use the Debug (KitProg3) configuration. If you are unfamiliar with how
to start a debug session with ModusToolbox IDE, see KBA224621.
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 2
Design and Implementation
This design consists of a PWM resource and a Smart I/O resource, both creating square waves of slightly different frequencies.
These square waves are routed through an exclusive-OR (XOR) gate within the Smart I/O resource, yielding a signal with a
gradually changing duty cycle. The rate of change is proportional to the difference between the output square wave frequencies.
The signal is then output to I/O4 of the Smart I/O port 9. Driving LED with this signal results in a “ramping” effect, where the LED
gradually get brighter and dimmer alternately.
The PWM is driven by a 10-kHz clock with a period of 399 counts and a compare value of 200 counts. This gives a 50 percent
duty cycle square wave with a 40-ms period. The Smart I/O is clocked at 99 Hz using a divided clock sourced from CLK_PERI.
This input clock is divided by 4 using the lookup tables (LUTs) of the Smart I/O resource to produce a square wave with a
40.4-ms period.
To generate a square wave signal with a time period close to 40 ms, a 99-Hz clock is divided by 4 using a synchronous sequential
circuit, which is realized using the LUTs of the Smart I/O resource.
To implement a divide-by-4 sequential circuit, consider the state transition values shown in Table 1:
Table 1. State Transition Table for a Divide-by-4 Sequential Circuit
CLK
Present State
Next State
D0
D1
Q0
Q1
Q0
Q1
0 0 1 1 1
1
1 1 0 1 0
1
0 1 1 0 1
0
1 0 0 0 0
0
From this state transition table, you can observe that Q0 is half the frequency of Clk_SmartIO and Q1 is 1/4th frequency of
Clk_SmartIO. This sequential logic can be implemented using the LUTs of the Smart I/O resource.
Figure 1 shows the implementation of this logic using LUT 2 and LUT 3. In addition, the divided clock is XORed with the PWM
output using LUT 4 to generate a signal with the duty cycle gradually increasing and decreasing over time. The output of LUT 4
is driven to I/O 4 output.
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 3
Figure 1. LUT Configuration and Timing Diagram
Q
Q
SET
CLR
D
99 Hz
LUT2
Q
Q
SET
CLR
D
LUT3 LUT4
chip 4 (TCPWM line)
I/O 4 (LED)
99 Hz
LUT2
output
LUT3
Output
(99/4 Hz)
LUT4
output
chip 4
PWM
output
D0
D1
Q0
Q1
Resources and Settings
Table 2 lists the ModusToolbox resources used in this example, and how they are used in the design. For pin usage and
configuration, open the Pins tab of the design.modus file.
Table 2. ModusToolbox Resources
Resource
Alias
Purpose
Timer Counter PWM (TCPWM)
PWM
Generates 25 Hz, 50% duty cycle square wave
Smart I/O
SmartIO
Implements divide-by-4 sequential circuit
Digital Output Pin
Pin_LED
Provides visual feedback using the LED
Figure 2 highlights the non-default settings for the TCPWM.
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 4
Figure 2. TCPWM Configuration
Figure 3 through Figure 5 illustrate the steps for configuring Smart I/O.
Figure 3. Enabling Smart I/O
Click to Launch the
SmartIO Configurator
Enable the Smart I/O Port 9
Enable Pin P9[4]
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 5
Figure 4. Smart I/O Routing Configuration
Figure 5. LUT Configuration
LUT Output Mapping
Figure 5 depicts the LUT2 configuration settings. Similarly, configure LUT3 and LUT 4 with the settings shown in Table 3.
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 6
Table 3. Smart I/O LUT Configuration
LUT#
Mode
LUT inputs
LUT
Output
Mapping
Description
TR2
TR1
TR0
LUT2
Sequential (gated) output
LUT2
LUT2
LUT2
0x01
Implements a logic NOT operation
LUT3
Sequential (gated) output
LUT3
LUT3
LUT2
0x81
Implements a logic XNOR operation
LUT4
Combinatorial output
LUT3
LUT3
Chip 4
0x42
Implements a logic XOR operation
Figure 6 and Figure 7 show the Peripheral-Clock configuration for Smart I/O and TCPWM resources respectively.
Figure 6. Peripheral-Clock Configuration for Smart I/O
Figure 7. Peripheral-Clock Configuration for TCPWM
Reusing This Example
This example is designed for the supported kits. To port the design to a different PSoC 6 MCU device, right-click an application
project and choose Change Device. If changing to a different kit, you may need to reassign pins.
Table 4. Device and Pin Mapping Table across PSoC 6 MCU Kits
Kit Name
Device Used
LED
CY8CKIT-062-BLE
CY8C6347BZI-BLD53
P13[7]
CY8CKIT-062-WiFi-BT
CY8C6247BZI-D54
P13[7]
CY8CPROTO-062-4343W
CY8C624ABZI-D44
P13[7]
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 7
In some cases, a resource used by a code example (for example, an IP block) is not supported on another device. In that case,
the example will not work. If you build the code targeted at such a device, you will get errors. See the device datasheet for
information on what a particular device supports.
Related Documents
For a comprehensive list of PSoC 6 MCU resources, see KBA223067 in the Cypress community.
Application Notes
AN210781 – Getting Started with PSoC 6 MCU
with Bluetooth Low Energy (BLE) Connectivity
Describes PSoC 6 MCU with BLE Connectivity devices.
AN215656 – PSoC 6 MCU: Dual-CPU System
Design
Describes the dual-CPU architecture in PSoC 6 MCU, and shows how to build a simple
dual-CPU design
Code Examples
Visit the Cypress GitHub site for a comprehensive collection of code examples using ModusToolbox IDE
Device Documentation
PSoC 6 MCU: PSoC 63 with BLE Datasheet
PSoC 6 MCU: PSoC 63 with BLE Architecture Technical Reference Manual
Development Kits
CY8CKIT-062-BLE PSoC 6 BLE Pioneer Kit
CY8CKIT-062-WiFi-BT PSoC 6 WiFi-BT Pioneer Kit
CY8CPROTO-062-4343W PSoC 6 Wi-Fi BT Prototyping Kit
Tool Documentation
ModusToolbox IDE
The Cypress IDE for IoT designers
Cypress Resources
Cypress provides a wealth of data at www.cypress.com to help you to select the right device, and quickly and effectively integrate
the device into your design.
For the PSoC 6 MCU devices, see KBA223067 in the Cypress community for a comprehensive list of PSoC 6 MCU resources
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 8
Document History
Document Title: CE219490 – PSoC 6 MCU Ramping LED using Smart I/O
Document Number: 002-25568
Revision
ECN
Orig. of
Change
Submission
Date
Description of Change
**
6373851
VKVK
11/02/2018
New code example
*A
6482040
VKVK
02/11/2019
Updated the project with ModusToolbox 1.1
PSoC 6 MCU Ramping LED using Smart I/O
www.cypress.com Document No. 002-25568 Rev.*A 9
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