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stm32,esp32: In machine_i2s, send null samples in underflow situations.

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Eliminate noise data from being sent to the I2S peripheral when the
transmitted sample stream is stopped.

Signed-off-by: Mike Teachman <mike.teachman@gmail.com>
This commit is contained in:
MikeTeachman
2021-09-24 20:06:10 -07:00
committed by Damien George
parent 6d9da27c21
commit 0be3b91f11
2 changed files with 4 additions and 0 deletions
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ports/stm32/machine_i2s.c
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@@ -509,6 +509,9 @@ STATIC void feed_dma(machine_i2s_obj_t *self, ping_pong_t dma_ping_pong) {
if (self->bits == 32) {
reformat_32_bit_samples((int32_t *)dma_buffer_p, SIZEOF_HALF_DMA_BUFFER_IN_BYTES / (sizeof(uint32_t)));
}
} else {
// underflow. clear buffer to transmit "silence" on the I2S bus
memset(dma_buffer_p, 0, SIZEOF_HALF_DMA_BUFFER_IN_BYTES);
}
// flush cache to RAM so DMA can read the sample data