ch32v307 DMX output!

dmx.c

#include "board.h"
#include "ch32v30x.h"
#include "dmx.h"
#include "debug.h"

uint8_t output_buffer[513];

/*
    dmx_init();
    dmx_send_break();
    dmx_dma_go();

    for(;;) {
        if(DMA_GetFlagStatus(DMA1_FLAG_TC7) != RESET) // Wait until USART2 TX DMA1 Transfer Complete
        {
            dmx_send_break();
            dmx_dma_go();
        }

    }
*/

void dmx_init() {
    for(int x = 0; x < 513; x++) {
        output_buffer[x] = 0;
    }

    GPIO_InitTypeDef  GPIO_InitStructure = {0};
    USART_InitTypeDef USART_InitStructure = {0};

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

     /* USART2 TX-->A.2   RX-->A.3 */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // Board specific, but this is the DE pin, which needs to be HIGH to output DMX
    // In this case, it's PB1
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
    GPIO_WriteBit(GPIOB, GPIO_Pin_1, Bit_SET);

    USART_InitStructure.USART_BaudRate = 250000;
    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
    USART_InitStructure.USART_StopBits = USART_StopBits_2;
    USART_InitStructure.USART_Parity = USART_Parity_No;
    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStructure.USART_Mode = USART_Mode_Tx;

    USART_Init(USART2, &USART_InitStructure);

    USART_Cmd(USART2, ENABLE);

    DMA_InitTypeDef DMA_InitStructure = {0};
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);   
}

void dmx_dma_go() {
    DMA_DeInit(DMA1_Channel7);
    DMA_InitTypeDef DMA_InitStructure = {0};
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)(&USART2->DATAR); /* USART2->DATAR:0x40004404 */
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)output_buffer;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = 513;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
    DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel7, &DMA_InitStructure);

    DMA_Cmd(DMA1_Channel7, ENABLE); /* USART2 Tx */

    USART_DMACmd(USART2, USART_DMAReq_Tx, ENABLE);
}

void dmx_send_break() {

    while(USART_GetFlagStatus(USART2, USART_FLAG_TC) == 0) {
        // printf("Waiting on TC\r\n");
    }

    USART_Cmd(USART2, DISABLE);

    GPIO_InitTypeDef  GPIO_InitStructure = {0};
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    GPIO_WriteBit(GPIOA, GPIO_Pin_2, Bit_RESET);
    Delay_Us(173); // We get an extra 5us out of the transactions, so we can BREAK for 173 and end up OK.

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    USART_Cmd(USART2, ENABLE);
    Delay_Us(8); // Delay through MAB to be sure we're up before we start DMAing data
}