topic Re: How to make edma read 16-bits MSB as pdm data width is 32-bits in i.MX Processors

How to make edma read 16-bits MSB as pdm data width is 32-bits

yalin — Mon, 18 Jul 2022 06:34:19 GMT

Dear support,

As I use RT1170, the PDM data width is 32-bits, but I just need a 16-bits audio data. And I'd like to use the pdm_sai_edma SDK for faster data transfer, how can I make edma read just 16-bits MSB of pdm data and then send it to s_buffer? (I can get 16-bits audio data by taking 16-bits MSB when 32-bits data get to s_buffer, but I perfer to do it as edma reading and then I just need to transfer half the amount of data)

Thanks.

Re: How to make edma read 16-bits MSB as pdm data width is 32-bits

Pavel_Hernandez — Thu, 21 Jul 2022 02:57:45 GMT

Hello,

I review the code about the s_buffer and I suggest changing the size of the buffer in macro [BUFFER_SIZE] to 2 bytes.

if (s_bufferValidBlock > 0) { pdmXfer.data = (uint8_t *)((uint32_t)s_buffer + s_readIndex * BUFFER_SIZE); pdmXfer.dataSize = BUFFER_SIZE; pdmXfer.linkTransfer = NULL; if (kStatus_Success == PDM_TransferReceiveEDMA(DEMO_PDM, &s_pdmRxHandle, &pdmXfer)) { s_readIndex++; } if (s_readIndex == BUFFER_NUMBER) { s_readIndex = 0U; } }

I hope this works for your application if you need more information please let me know.

Best regards,
Pavel

Re: How to make edma read 16-bits MSB as pdm data width is 32-bits

yalin — Fri, 22 Jul 2022 01:50:05 GMT

Hello Pavel_Hernandez,

Do you mean to modify code like the following in pdm_sai_edma.c?

#define BUFFER_SIZE (16)

When I do it, the demo will be blocked, and the log is like the following.

PDM SAI Edma example started!
ASSERT ERROR " fsl_edma.c:1013 : (transferBytes % bytesEachRequest) == 0U

Re: How to make edma read 16-bits MSB as pdm data width is 32-bits

Pavel_Hernandez — Fri, 22 Jul 2022 20:14:37 GMT

Hello,

The number indicated in the macro BUFFER_SIZE is in bytes, 2 bytes for 16 bits, but recently the IDE [11.6] and the SDK [2.12] were updated, could you try to use the new version, I saw this change for this.

xfer.dataSize = BUFFER_SIZE * 2U;

Best regards,
Pavel