FreeRTOS SMP Template for Raspberry Pi Pico Board

Introduction

Raspberry Pi Pico is a low-cost, high-performance microcontroller board with flexible digital interfaces.

Key features include:

• RP2040 microcontroller chip designed by Raspberry Pi in the United Kingdom

• Dual-core Arm Cortex M0+ processor, flexible clock running up to 133 MHz

• 264KB of SRAM, and 2MB of on-board Flash memory

• Castellated module allows soldering direct to carrier boards

• USB 1.1 with device and host support

• Low-power sleep and dormant modes

• Drag-and-drop programming using mass storage over USB

• 26 × multi-function GPIO pins

• 2 × SPI, 2 × I2C, 2 × UART, 3 × 12-bit ADC, 16 × controllable PWM channels

• Accurate clock and timer on-chip

• Temperature sensor

• Accelerated floating-point libraries on-chip

• 8 × Programmable I/O (PIO) state machines for custom peripheral support

• Introduction to Symmetric Multiprocessing (SMP) with FreeRTOS
• Port from FreeRTOS non-SMP version to FreeRTOS SMP version

Building and Running the RTOS Template Applications

Building

• Setup the Raspberry Pi Pico SDK build environment by following the instructions for Getting Started With Pico.
• To compile this project firstly initialize and update the submodules:

 git submodule update --init

• Ensure that PICO_SDK_PATH is set in your environment, or pass it via -DPICO_SDK_PATH=xxx on the CMake command line.
• Run the following commands:

$ mkdir build
$ cd build
$ cmake ..
$ make

This will generate .uf2 files for each Template application: build/pico-freertos.uf2

Running

1. Connect the Raspberry Pi Pico to your computer while holding the BOOTSEL button. This will force the board into USB Mass Storage Mode.
2. Drag-and-drop the .uf2 file for the template you want to run onto the Mass Storage Device.

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RTOS Configuration and Usage Details

• Configuration items specific to the template are contained in include/FreeRTOSConfig.h.
• The constants defined in these files can be edited to suit your application.
• The following configuration options are specific to the SMP support in the FreeRTOS Kernel:
  • configNUM_CORES - Set the number of cores.
  • configRUN_MULTIPLE_PRIORITIES - Enable/Disable simultaneously running tasks with multiple priorities.
  • configUSE_CORE_AFFINITY - Enable/Disable setting a task's affinity to certain cores.
  • Source/Portable/MemMang/heap_4.c is included in the project to provide the memory allocation required by the RTOS kernel. Please refer to the Memory Management section of the API documentation for complete information.
• vPortEndScheduler() has not been implemented.