Posted on July 13, 2016 at 18:56Hi, I am working with the STM32F4 discovery board and I'm trying to use the built in codec. I am trying to configure it to play audio from 2 alternating buffers I create. I have set up my callback function to start playing the next buffer once the previous buffer is finished. Currently for testing purposes I set all values in one buffer to 0 and all in the other to 32767, which creates a crude square wave, but I am not getting any audio out, can anyone see what I am missing?
I start audio playback in my main via:
&sharpdefine MY_BUFSIZE 1024
static volatile uint8_t nextbuf;
static volatile uint16_t bufferNumber;
static int16_t buf0[MY_BUFSIZE];
static int16_t buf1[MY_BUFSIZE];
int main(void){
SystemInit();
EVAL_AUDIO_SetAudioInterface(AUDIO_INTERFACE_I2S);
EVAL_AUDIO_Init(OUTPUT_DEVICE_BOTH, 100, 48000);
compute_buffer(buf0, MY_BUFSIZE, 0);
compute_buffer(buf1, MY_BUFSIZE, 1);
Audio_MAL_Play((uint32_t)buf0, MY_BUFSIZE / 2);
//EVAL_AUDIO_Play((uint16_t*)buf0, MY_BUFSIZE/2);
while(1){
}
}
Here is my callback function:
void EVAL_AUDIO_TransferComplete_CallBack(uint32_t pBuffer, uint32_t Size)
{
if(nextbuf == 0) { ;
Audio_MAL_Play((uint32_t)buf0, MY_BUFSIZE);
nextbuf = 1;
} else {
Audio_MAL_Play((uint32_t)buf1, MY_BUFSIZE);
nextbuf = 0;
}
}
Here is how I fill the buffers:
void compute_buffer(int16_t *pbuf, int bufsize, uint16_t bufferNumber)
{
int i;
for(i = 0; i < bufsize / 2; i+=2) {
pbuf[i] = bufferNumber * 32767;
pbuf[i + 1] = bufferNumber * 32767;
}
}
Do I need to use the DAC instead of I2S, or is there something else I need to configure? I was having a hard time finding how the EVAL_AUDIO_TransferComplete_CallBack function is connected to the Audio_MAL_Play function. I also tried using EVAL_AUDIO_Play, with the same results.
#stm32f4discovery-audio-codec
