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Ensure STM32_I2S_AddSamples starts playback if there isn't enough space,

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fix issue where calling AddSamples with too big a buffer would always cause failure
This commit is contained in:
Gordon Williams 2024-12-05 10:08:54 +00:00
parent 0a8ad236b5
commit acf9482c1d
2 changed files with 29 additions and 5 deletions
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28
libs/pipboy/stm32_i2s.c
View File

@ -244,10 +244,13 @@ int STM32_I2S_GetFreeSamples() {
// Add samples to the ringbuffer
void STM32_I2S_AddSamples(int16_t *data, unsigned int count) {
int timeout = 1000000;
while ((STM32_I2S_GetFreeSamples() < (int)count+32) && --timeout); // wait here for space
// Try and fill until ringbuffer is full
unsigned int freeSamples = STM32_I2S_GetFreeSamples();
unsigned int c = count;
if (c > freeSamples) {
c = freeSamples;
count -= freeSamples;
} else count = 0;
while (c--) {
audioRingBuf[audioRingIdxIn] = *(data++)
+ (audioRingIdxIn&1); // add 1 bit of noise to stop DAC from turning off!
@ -255,8 +258,8 @@ void STM32_I2S_AddSamples(int16_t *data, unsigned int count) {
}
//jsiConsolePrintf("add %d %d %d %d\n", i2sDMAidx, i2sStatus, count, audioRingBufGetSamples());
// start playback when we have enough
if (i2sStatus == STM32_I2S_STOPPED && audioRingBufGetSamples()>I2S_DMA_BUFFER_SIZE*3) {
// start playback if we have enough
if (i2sStatus == STM32_I2S_STOPPED && audioRingBufGetSamples()>=I2S_DMA_BUFFER_SIZE*3) {
// if audioRingBufGetSamples()>I2S_DMA_BUFFER_SIZE*3 we should have enough here to fill 6 buffers
i2sDMAidx = !DMA_GetCurrentMemoryTarget(DMA1_Stream4);
fillDMAFromRingBuffer(); // fill the first buffer with what we're currently reading from!
@ -264,6 +267,21 @@ void STM32_I2S_AddSamples(int16_t *data, unsigned int count) {
fillDMAFromRingBuffer(); // fill the second buffer
STM32_I2S_Start();
}
if (!count) return;
// otherwise we still have more to put in - try and wait a bit
if (STM32_I2S_GetFreeSamples() < (int)count) {
// wait until we have space
int timeout = 1000000;
while ((STM32_I2S_GetFreeSamples() < (int)count) && --timeout); // wait here for space
}
// now attempt to put in the rest but drop any we don't have space for
c = count;
while (c-- && STM32_I2S_GetFreeSamples()) {
audioRingBuf[audioRingIdxIn] = *(data++)
+ (audioRingIdxIn&1); // add 1 bit of noise to stop DAC from turning off!
audioRingIdxIn = (audioRingIdxIn+1) & (I2S_RING_BUFFER_SIZE-1);
}
}
void STM32_I2S_Start() {

6
libs/pipboy/stm32_i2s.h
View File

@ -22,6 +22,12 @@
#define I2S_RING_BUFFER_SIZE 8192 // size of ringbuffer used for audio input in u16
// 8192 seems fine to use - still enough for 8 DMA packets worth/0.5sec...
/* jswrap_pb_audioFrame sends data in 2048 byte chunks and STM32_I2S_AddSamples
starts playback at 3*I2S_DMA_BUFFER_SIZE. So I2S_RING_BUFFER_SIZE=8192
is the least we can use, since any less and 3*I2S_DMA_BUFFER_SIZE would be
big enough that the next sample from jswrap_pb_audioFrame would fill the buffer */
typedef enum {
STM32_I2S_STOPPED,
STM32_I2S_PLAYING