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Individually Addressable LEDs

Example code using the onboard DSP, FreeRTOS, and DMA to control individually addressable LEDs (SK6812). This project has both non-audio patterns and audio syncing patterns.

Non-audio syncing patterns: https://youtu.be/5Bn3eNN9Ki0

Setup + Audio syncing patterns: https://youtu.be/zrTWR6r1QTw

Architecture

The idea is to use 2 different tasks to manage the LEDs. The tasks are listed below by priority (higher numbers will preempt lower numbers). I realize they could probably all be combined into one task, but more tasks means more learning.

  1. Idle Task
    • Does nothing
  2. Pattern Task
    • Decides what pattern to show
    • Calculates RGB color based on selected pattern
    • 10ms (100 Hz)
  3. Refresh Task
    • Refreshes the actual colors shown on the LED strip
      • Initiates PWM pulse train
    • 10ms (100 Hz)

Peripherals

Timers

Timer 2: 44.1 kHz timer for sampling audio voltage data 
Timer 4: LED Data Line
Timer 12: Collects runtime statistics (task time, computation times, ...)

GPIO:

C4: Audio voltage data in
B6: LED Data out
D12: LED4 (GRN) - Indicates stack overflow for vCreatePattern
D13: LED3 (ORG) - Indicates stack overflow for vUpdateLedStrip
D14: LED5 (RED)
D15: LED6 (BLU)

DMA:

DMA1 Stream 0: Transfer duty cycles to PWM module.
DMA2 Stream 0: Transfer ADC1->DR to buffers (used in double buffer mode).

ADCs:

ADC1 Channel 14: Samples audio voltage

Resources

https://www.st.com/content/ccc/resource/technical/layouts_and_diagrams/schematic_pack/group1/60/36/18/8c/71/30/45/dc/MB997-F407VGT6-E01_Schematic/files/MB997-F407VGT6-E01_Schematic.pdf/jcr:content/translations/en.MB997-F407VGT6-E01_Schematic.pdf

https://www.st.com/resource/en/user_manual/dm00039084-discovery-kit-with-stm32f407vg-mcu-stmicroelectronics.pdf

http://socialledge.com/sjsu/index.php/FreeRTOS_Tutorial

https://www.freertos.org/a00125.html

https://cdn-shop.adafruit.com/product-files/1138/SK6812+LED+datasheet+.pdf

https://www.iar.com/support/resources/articles/using-iar-embedded-workbench-for-arm-and-the-cmsis-dsp-library/

https://stm32f4-discovery.net/2014/10/stm32f4-fft-example/

https://www.keil.com/pack/doc/CMSIS/DSP/html/group__RealFFT.html#ga5d2ec62f3e35575eba467d09ddcd98b5

https://community.st.com/s/question/0D50X00009XkibiSAB/stm32f207-adctimerdma-poor-peripheral-library-examples

https://arm-software.github.io/CMSIS_5/DSP/html/index.html

https://www.freertos.org/FreeRTOS-Coding-Standard-and-Style-Guide.html

Notes

Use xTaskCreateStatic to create a task with the stack in a static location

Use xTaskCreate to create a task with the stack in a dynamic location

Use vTaskDelayUntil to schedule task to be run again

Use uxTaskGetStackHighWaterMark to see the highest of stack usage

Use taskENTER_CRITICAL to disable interrupts and tasks

Use taskEXIT_CRITICAL to re-enable interrupts and tasks

Use portTICK_PERIOD_MS to determine period of one clock tick/cycle