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nrf: i2sout: Only update hold_value when appropriate 

If we put no samples into the buffer, then there is no last
sample to fill out hold_value with.  (and, in fact, the expression such
as *(uint32_t*)(buffer-4) is outside an allocated region)

Detect this condition, and leave the prior value in place.

This improves clicks heard when pausing and resuming a waveform.
This commit is contained in:
Jeff Epler 2019-11-22 13:54:37 -06:00
parent c000567d88
commit aabb56c840
1 changed files with 12 additions and 9 deletions
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21
ports/nrf/common-hal/audiobusio/I2SOut.c
View File

@ -108,6 +108,7 @@ void choose_i2s_clocking(audiobusio_i2sout_obj_t *self, uint32_t sample_rate) {
static void i2s_buffer_fill(audiobusio_i2sout_obj_t* self) {
void *buffer = self->buffers[self->next_buffer];
void *buffer_start = buffer;
NRF_I2S->TXD.PTR = (uintptr_t)buffer;
self->next_buffer = !self->next_buffer;
size_t bytesleft = self->buffer_length;
@ -157,15 +158,17 @@ static void i2s_buffer_fill(audiobusio_i2sout_obj_t* self) {
// Find the last frame of real audio data and replicate its samples until
// you have 32 bits worth, which is the fundamental unit of nRF I2S DMA
if (self->bytes_per_sample == 1 && self->channel_count == 1) {
// For 8-bit mono, 4 copies of the final sample are required
self->hold_value = 0x01010101 * *(uint8_t*)(buffer-1);
} else if (self->bytes_per_sample == 2 && self->channel_count == 2) {
// For 16-bit stereo, 1 copy of the final sample is required
self->hold_value = *(uint32_t*)(buffer-4);
} else {
// For 8-bit stereo and 16-bit mono, 2 copies of the final sample are required
self->hold_value = 0x00010001 * *(uint16_t*)(buffer-2);
if(buffer != buffer_start) {
if (self->bytes_per_sample == 1 && self->channel_count == 1) {
// For 8-bit mono, 4 copies of the final sample are required
self->hold_value = 0x01010101 * *(uint8_t*)(buffer-1);
} else if (self->bytes_per_sample == 2 && self->channel_count == 2) {
// For 16-bit stereo, 1 copy of the final sample is required
self->hold_value = *(uint32_t*)(buffer-4);
} else {
// For 8-bit stereo and 16-bit mono, 2 copies of the final sample are required
self->hold_value = 0x00010001 * *(uint16_t*)(buffer-2);
}
}
// Emulate pausing and stopping by filling the DMA buffer with copies of