I'm looking at the SDK15 I2S example project using DMA. My dev set up is 52840/Keil.
The project is under: \nRF5_SDK_15.0.0_a53641a\examples\peripheral\i2s
In the callback function which is called when DMA completes and the new buffer needs to be set, the data structure being set to i2s driver (nrf_drv_i2s_next_buffers_set) is not updated to use the alternating buffer but the same one. Lookes like DMA will keep using the same memory buffer every time. Is that a bug?
static void data_handler(nrf_drv_i2s_buffers_t const * p_released,
uint32_t status)
{
// 'nrf_drv_i2s_next_buffers_set' is called directly from the handler
// each time next buffers are requested, so data corruption is not
// expected.
ASSERT(p_released);
// When the handler is called after the transfer has been stopped
// (no next buffers are needed, only the used buffers are to be
// released), there is nothing to do.
if (!(status & NRFX_I2S_STATUS_NEXT_BUFFERS_NEEDED))
{
return;
}
// First call of this handler occurs right after the transfer is started.
// No data has been transferred yet at this point, so there is nothing to
// check. Only the buffers for the next part of the transfer should be
// provided.
if (!p_released->p_rx_buffer)
{
nrf_drv_i2s_buffers_t const next_buffers = {
.p_rx_buffer = m_buffer_rx[1],
.p_tx_buffer = m_buffer_tx[1],
};
APP_ERROR_CHECK(nrf_drv_i2s_next_buffers_set(&next_buffers));
mp_block_to_fill = m_buffer_tx[1];
}
else
{
mp_block_to_check = p_released->p_rx_buffer;
// The driver has just finished accessing the buffers pointed by
// 'p_released'. They can be used for the next part of the transfer
// that will be scheduled now.
APP_ERROR_CHECK(nrf_drv_i2s_next_buffers_set(p_released));
// The pointer needs to be typecasted here, so that it is possible to
// modify the content it is pointing to (it is marked in the structure
// as pointing to constant data because the driver is not supposed to
// modify the provided data).
mp_block_to_fill = (uint32_t *)p_released->p_tx_buffer;
}
}
