Lesson 3 – PSoC 6 Introduction: FreeRTOS and a Debugging UART

PSoC 6 Introduction

# Title Comment
0 A Two Hour PSoC 6 Class An introduction to the PSoC 6 class with links to all of the documents
1 Resources Links to all of the Cypress PSoC 6 information including videos, application notes etc.
2 Your First Project Learn how to build a PSoC 6 project and program your CY8CKIT-062-BLE development kit
3 FreeRTOS and a Debugging UART Build a project using FreeRTOS including a debug console with the UART
4 CapSense Build a project using the Mutual Cap Buttons and Self Cap Slider
5 Bluetooth Low Energy Build a CapSense project using BLE and CySmart

All of the projects are available at git@github.com:iotexpert/psoc-6-introduction.git or www.github.com/iotexpert/psoc-6-introduction

Project Description

This project will show you how to build a PSoC 6 project that is running FreeRTOS and printing information to the debugging UART

How does it work?

The PSoC 6 is a very capable, fast dual Coretex-M MCU.  In order to manage your design complexity that can be attacked with this chip, we gave you the ability to use a Real Time Operating System – FreeRTOS.  With a few simple clicks it will startup for you.

The CY8CKIT-062-BLE has a KitProg-2 Debugger/Programmer on board.  In addition to Program/Debug it can also serve as a USB <–> UART bridge which will allow you to open a terminal program on your PC to do Input/Output with a UART in the PSoC 6.

How am I going to do it?

  1. Copy “MyFirstDesign” to Start a New Project
  2. Modify the Build Settings to add Debug Printing and FreeRTOS
  3. Add the UART to the Schematic and Assign the Pins
  4. Create the UART Test Firmware
  5. Program and Test the Debug UART
  6. Modify firmware for FreeRTOS
  7. Program and Test
  8. A Tour of PDL for the TCPWM

Copy “MyFirstDesign” to Start a New Project

Right click on “MyFirstDesign” and select “Copy”

PSoC Creator Copy Project

Then right click on the workspace and select “Paste”

PSoC Creator Copy/Paste

Then right click on “MyFirstDesign_Copy_01” and select rename.  Then type in a reasonable name like “FreeRTOS-UART”

PSoC Creator Copy / Paste

PSoC Creator will ask you about some files.  Just click “Rename”

PSoC Creator Rename

Now you will have three projects in your workspace.  I typically click “Program” which will build the copied project and program the development kit… just to make sure that stuff still works.

PSoC Creator Workspace

Modify the build settings to add debug printing and FreeRTOS

You can build massively complex systems with PSoC 6.  In order to help manage that complexity I like to turn on debug printing so that “printf” works.  I also like to use a Real Time Operating System (FreeRTOS).  PSoC Creator has both of these things built in.  We called the printf functionality “Retarget I/O” because you need to “target” the Input / Output of the printf … aka STDIN and STDOUT to a peripheral in the PSoC.  The best peripheral to use for printf is the UART that is attached to your computer via kitprog2.

To add printf and FreeRTOS to your project you need to: Right click on the project and select “Build Settings…”

PSoC Creator Modify Build Settings

Click on the Peripheral Driver Library and then select “FreeRTOS” and “Memory Management heap_4”.  Then select “Retarget I/O”.  When you build your project this will cause PSoC Creator to add both of these to your project.

PSoC Creator Build Settings FreeRTOS

Select Build->Generate Application and notice that PSoC Creator added a number of files to your project including the FreeRTOS, stdio_user.c/.h and retarget_io

PSoC Creator retarget_io.c

Add the UART to the Schematic and Assign the Pins

In order to printf, getchar and putchar  you need to attach c standard library stdin and stdout to “something”.  The best “something” is the UART that is attached to the KitProg2 which is attached to your computer.  Then you can open a terminal program (like Putty) and read and write to the PSoC.

So, to do this you need to add a UART to your design schematic from the component catalog.  In the picture below I just typed “uart” in the search box.

PSoC Creator Debug UART

What pins on the PSoC 6 BLE is the UART attached to?  Well… if you turn over your CY8CKIT-062-BLE you will find a little map that show that the PSoC 6 BLE UART is attached to the PSoC 5LP UART.  The PSoC 5LP is programmed with the KitProg2 firmware.


To attach those pins in your firmware you just double click on the “Pins” tab in the DWR.  Then you can select “Port” for the UART RX and TX.  Look at the picture below.

PSoC 6 PSoC Creator Pin Settings

Now that I have all of that done, I run “Build->Generate Application” to get all of the new settings into my project.

Create the UART Test Firmware

The next step in making the printf work is to “retarget” it to the UART we just put in the schematic.  Open “stdio_user.h” and add “include <project.h>” (line 130) and change IO_STDOUT_UART and IO_STDIN_UART to be UART_1_HW.  The name “UART_1” on lines 136-137

Now edit your main_cm4.c to:

  • Turn on the UART with UART_1_Start() on line
  • Then a couple of printfs lines 24-25

Note that “\033[2J\033[H” is just a VT100 escape sequence for clear screen and go home.

Program and Test the Debug UART

You need to figure out which com port that the KitProg2 is attached to.  To do this run the device manager by pressing the “windows” button then typing “device manger”

Device Manager

Click on ports.  Then you can see that the programmer is “KitProg2” and that the UART is attached to COM9 (everyone will have a different number)

Device Manager

Run Putty (or  your favorite terminal program)


Press the program button on PSoC Creator and you should see your test print

Putty PSoC 6 UART

Modify firmware for FreeRTOS

When I look out the output window from the previous step you can see that there is a warning message from FreeRTOS.  Lets fix that warning (by deleting line 83).  While we are at it, lets change the heap size to 48K (48*1024)

Now lets turn on FreeRTOS. Double click on main_cm4.c to open it in the code editor.

Modify FreeRTOS Firmware

Add the following firmware to your project.

The uartTask is function that FreeRTOS uses to create a Task.  This task will control the uart. (which is amazingly enough why I named it uartTask)

  • The function call “setvbuff” turns of buffering on stdin… which means every character will immediately come through to your program
  • getchar just gets a character from the terminal
  • the ‘s’ and ‘S’ will start and stop the PWM (more to follow)

In main I

  • Create a task for the uartTask (line 56)
  • Start FreeRTOS (line 57)

How did I figure out how to start/stop the PWM?  To find the documentation for “PDL” aka the Peripheral Driver Library, you can right click on the component in the schematic and select “Open PDL Documentation”


Or you can open “Help –> Documentation –> Peripheral Driver Library”

PSoC Creator Help

In the documentation I can see all kind of functions, including “Cy_TCPWM_PWM_Disable”


Program and Test

PSoC 6 FreeRTOS Test

A Tour of PDL for the TCPWM

How did I figure out that the TCPWM_Type *base should be “UART_1_HW”?  ….. well …. You might ask yourself, “What does PWM_1_Start()” do?  It just calls PDL start function.  OK… so what does that do?  To find out you can right click on the “PWM_1_Start” function and select “Go To Definition” which will take you to the source code.

PSoC 6 Tour of PDL

You will end up in a file called “PWM_1.c”.  This file was created for you automatically by PSoC Creator.   This function is really simple.

  • If it has never been initialized then it calls init (lines 15-19)
  • Then it enables the TCPWM (line 22)
  • Then if there not an external pin on the PWM, then it causes a software trigger (line 25)

So, you might ask yourself what is “PWM_1_HW”?  Well this is just the base address of the registers for the PWM_1.  Lets follow that.  Right click on it and go to definition.


This will take you to PWM_1.h and you will see PWM_1_HW is setup as PWM_1_TCPWM_HW.  What is that?  Well do the right click thing again and find out.


This will take you to “cyfitter.h” which is the output of the place and route.  It tell you that PWM_1_TCP is really TCPWM0