DMA control of GPIO pins on Particle Photon STM32

main.cpp

#include "Particle.h"

// RM0033 MANUAL - Table 23 / Figure 1 System architecture
// Photon is STM32F205
// Only DMA2 is connected with GPIO ports https://stackoverflow.com/questions/46613053/pwm-dma-to-a-whole-gpio
// GPIO BSSRL/BSSRH/BSSR http://hertaville.com/stm32f0-gpio-tutorial-part-1.html
// DMA_Mode_Circular https://github.com/monkbroc/particle-speaker
// Ulrich Radig OctoArtnetNode https://www.ulrichradig.de/home/index.php/dmx/8-kanal-art-net
// Thanks to Julien Vanier for the idea of BSRR manipulation.

// The timers connected to APB2 are clocked from TIMxCLK up to 120 MHz
// In case of the Photon: TIM1, TIM8.

//SYSTEM_MODE(MANUAL); // only use this when you build local

// D7 is GPIO pin 13 on GPIOA.
uint16_t pinMask = 1<<13; // pin 13 on GPIOA (same as 0b0010000000000000)

uint16_t bufferSize = 4;
uint16_t blink_turnhigh_buffer[4];
uint32_t blink_bsrr_buffer0[4];
uint32_t blink_bsrr_buffer1[4]; // double buffer

void timerInit();
void dmaInit();

void setup() { // Put setup code here to run once

    delay(2000);
    Serial.begin(57600);

    timerInit();
    dmaInit();

    pinMode(D7, OUTPUT);

    //WiFi.off();

    // D7 is GPIO pin 13 on GPIOA.
    // of course you can modify multiple pins if you want
    // for example 0b0000000010100000 would turn on A3 and A5 (don't forget to modify the pinMask);
    blink_turnhigh_buffer[0] = 1<<13; //(same as 0b0010000000000000)
    blink_turnhigh_buffer[1] = 0;
    blink_turnhigh_buffer[2] = 1<<13;
    blink_turnhigh_buffer[3] = 0;

    // We use a XOR operation to mask and make the turn to LOW register low
    // (Done by sending a one. )
    for(int i = 0; i < 4; i++) {

      blink_bsrr_buffer0[i] = blink_turnhigh_buffer[i] + ((blink_turnhigh_buffer[i] ^ pinMask) << 16);
      blink_bsrr_buffer1[i] = blink_bsrr_buffer0[i]; // double buffer

    }
}

void loop() {

}

void timerInit (void) {

  // https://github.com/pkourany/SparkIntervalTimer/blob/master/src/SparkIntervalTimer.cpp
  // tryout with a slow timer. 2Hz (so each number is 0.5ms)
  //const uint16_t SIT_PRESCALERu = (uint16_t)(SYSCORECLOCK / 1000000UL) - 1;	//To get TIM counter clock = 1MHz
  const uint16_t SIT_PRESCALERm = (uint16_t)(SystemCoreClock / 2000UL) - 1;	  //To get TIM counter clock = 2KHz

  TIM_TimeBaseInitTypeDef	TIM_TimeBaseStructure;

  TIM_DeInit(TIM8);

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8, ENABLE);

  TIM_TimeBaseStructure.TIM_Prescaler = SIT_PRESCALERm;
  //TIM_TimeBaseStructure.TIM_Prescaler = SIT_PRESCALERu;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period =  2000;
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

  TIM_TimeBaseInit(TIM8,&TIM_TimeBaseStructure);
  TIM_ClearFlag(TIM8,TIM_FLAG_Update);

  TIM_Cmd(TIM8, ENABLE);

}

void dmaInit(void) {

  // DMA2 only connects to GPIO ports...
  // DMA2 channel 7 stream 1 connects to TIM8_UP
  DMA_InitTypeDef DMA_InitStructure;

  // Clock enable
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);

  DMA_Cmd(DMA2_Stream1, DISABLE);
  DMA_DeInit(DMA2_Stream1);

  DMA_StructInit(&DMA_InitStructure);

  DMA_InitStructure.DMA_Channel = DMA_Channel_7;
  DMA_InitStructure.DMA_PeripheralBaseAddr = ((uint32_t)&(GPIOA->BSRRL));
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t) blink_bsrr_buffer0;
  DMA_InitStructure.DMA_BufferSize = bufferSize;

  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;

  DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;

  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;

  /* Configure double buffering */
  DMA_DoubleBufferModeConfig(DMA2_Stream1, (uint32_t) blink_bsrr_buffer1, DMA_Memory_1);
  DMA_DoubleBufferModeCmd(DMA2_Stream1, ENABLE);

  DMA_Init(DMA2_Stream1, &DMA_InitStructure);

  DMA_Cmd(DMA2_Stream1, ENABLE);

  // DMA-Timer8 enable
  TIM_DMACmd(TIM8,TIM_DMA_Update,ENABLE);

}