Solved
F4 I2S cannot resync after noise
I've got the I2S working with DMA as slave receiver, works great, bit perfectly fills receiving buffer,
until I restart the master, or introduce noise to I2S bus, then it just loses it, fills buffer with nonsense after that.
It's not able to resync to same valid signal that was working previously.
Sure I expect to lose some frames, life happens to input signal, it should be able to resync.
So how can I make it resync?
I know that errata says I have to wait for WS high before enabling DMA, but what about after corruption?
I don't even know when the signal is invalid since there is no checksum,
I can't ask the user restart the device until it starts working..
Some audiophile DACs take I2S signal over cable, so anything could happen to it.
hi2s2.Instance = SPI2;
hi2s2.Init.Mode = I2S_MODE_SLAVE_RX;
hi2s2.Init.Standard = I2S_STANDARD_PHILIPS;
hi2s2.Init.DataFormat = I2S_DATAFORMAT_32B;
hi2s2.Init.MCLKOutput = I2S_MCLKOUTPUT_DISABLE;
hi2s2.Init.AudioFreq = I2S_AUDIOFREQ_44K;
hi2s2.Init.CPOL = I2S_CPOL_LOW; /* idle low clock */
hi2s2.Init.ClockSource = I2S_CLOCK_EXTERNAL; /* not PLL */
hi2s2.Init.FullDuplexMode = I2S_FULLDUPLEXMODE_ENABLE;
hdma_spi2_rx.Instance = DMA1_Stream3;
hdma_spi2_rx.Init.Channel = DMA_CHANNEL_0;
hdma_spi2_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_spi2_rx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_spi2_rx.Init.MemInc = DMA_MINC_ENABLE;
hdma_spi2_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD; /* 16 even for 32bit */
hdma_spi2_rx.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
hdma_spi2_rx.Init.Mode = DMA_CIRCULAR;
hdma_spi2_rx.Init.Priority = DMA_PRIORITY_VERY_HIGH;
hdma_spi2_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
ASSERT(HAL_DMA_Init(&hdma_spi2_rx) == HAL_OK);
__HAL_LINKDMA(&hi2s2, hdmarx, hdma_spi2_rx);
/* DMA1_Stream3_IRQn interrupt configuration */
HAL_NVIC_SetPriority(DMA1_Stream3_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA1_Stream3_IRQn);
ASSERT(HAL_I2SEx_TransmitReceive_DMA(&hi2s2, (tUI16 *)dmaTxBuf, (tUI16 *)dmaRxBuf, DMA_BUFF_LEN) == HAL_OK);