dac_dma.c

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#include "dac.h"
 
#ifdef DAC_USE_DMA
 
#include <GPDMA_LPC17xx.h>
#include <LPC17xx.h>
#include <stdbool.h>
 
_PRIVATE u8 dma_channel;
_PRIVATE bool dma_ok;
 
enum
{
    // DAC_CFG_DOUBLEBUF = 0x2,
 
    DAC_CFG_USE_CNT = 0x4,
 
    DAC_CFG_USE_DMA = 0x8,
} DAC_DMAConfig;
 
void DAC_InitDMA(u32 sample_rate_hz)
{
    LPC_DAC->DACCTRL |= (DAC_CFG_USE_DMA | DAC_CFG_USE_CNT);
    LPC_DAC->DACCNTVAL = sample_rate_hz;
 
    GPDMA_Initialize();
    dma_channel = 1;
    dma_ok = false;
}
 
void DAC_DeinitDMA(void)
{
    LPC_DAC->DACR = 0;
    LPC_DAC->DACCTRL &= ~(DAC_CFG_USE_DMA | DAC_CFG_USE_CNT);
    LPC_DAC->DACCNTVAL = 0;
    GPDMA_Uninitialize();
}
 
// PLAY FUNCTION & PRIVATE STUFF
 
_PRIVATE void dma_transfer_complete_callback(u32 event)
{
    dma_ok = (event & GPDMA_EVENT_TERMINAL_COUNT_REQUEST) != 0;
    DAC_StopDMA();
}
 
void DAC_PlayDMA(const u16 *const pcm_samples, u32 sample_count)
{
    if (!pcm_samples || sample_count == 0)
        return;
 
    const u32 status = GPDMA_ChannelConfigure(dma_channel, (u32)pcm_samples, (u32)&LPC_DAC->DACR, sample_count,
                                              GPDMA_CH_CONTROL_SI | GPDMA_CH_CONTROL_DI | GPDMA_WIDTH_HALFWORD,
                                              GPDMA_CONFIG_E, dma_transfer_complete_callback);
 
    if (status != 0)
        return;
 
    if (GPDMA_ChannelEnable(dma_channel) != 0)
        return;
}
 
void DAC_StopDMA(void)
{
    GPDMA_ChannelDisable(dma_channel);
}
 
#endif