ARM, RISC-V контроллеры

вот, например:

void
i2c_writebytes_start(int addr, const void* src, int len)
{
    txdma->CNDTR = len;
    txdma->CPAR = (int)&I2C1->TXDR;
    txdma->CMAR = (int)src;
    txdma->CCR  = DMA_CCR_MINC
                | DMA_CCR_DIR
                | DMA_CCR_EN;
    I2C1->CR2   = I2C_CR2_AUTOEND
                | (len << I2C_CR2_NBYTES_Pos)
                | addr;
    I2C1->CR2   |= I2C_CR2_START;
}