S32KのトピックRe: s32k312: Lpspi SyncTransmit with NULL Tx buffer

s32k312: Lpspi SyncTransmit with NULL Tx buffer

PaoloRB — Tue, 20 May 2025 23:33:48 GMT

Hi, I'm using the lpspi driver (sdk5.0) to read the device ID from an external flash. Running Lpspi_Ip_SyncTransmit passing both Tx and Rx buffers works well, but we I try to first sent the Tx buffer and after the Rx buffer it does not work as expected.

WORK:

spiTxBuffer[0] = 0x9F;

lpspi_status = Lpspi_Ip_SyncTransmit(&MASTER_1, spiTxBuffer, spiRxBuffer, 4, TIMEOUT);

NOT WORKS:

spiTxBuffer[0] = 0x9F;

lpspi_status = Lpspi_Ip_SyncTransmit(&MASTER_1, spiTxBuffer, NULL, 1, TIMEOUT);

lpspi_status = Lpspi_Ip_SyncTransmit(&MASTER_1, NULL, spiRxBuffer, 3, TIMEOUT);

Is anything I'm missing?

Thanks in advance for any clarification.

Re: s32k312: Lpspi SyncTransmit with NULL Tx buffer

PetrS — Wed, 21 May 2025 13:23:38 GMT

Hi,

you can use HalfDuplex API or ignore received data and send dummy 0xFF for full duplex operation. See suggestion in https://community.nxp.com/t5/S32K/S32K314-SPI-flash-implementation/m-p/1618490/highlight/true#M21501

BR, Petr

Re: s32k312: Lpspi SyncTransmit with NULL Tx buffer

PaoloRB — Wed, 21 May 2025 22:54:44 GMT

To make it works, I need to UpdateTransferParam (Full duplex).

spiTxBuffer[0] = 0x9F;

param.FirstCmd = TRUE;

param.KeepCs = TRUE;

Lpspi_Ip_UpdateTransferParam(&MASTER_1, &param);

lpspi_status = Lpspi_Ip_SyncTransmit(&MASTER_1, spiTxBuffer, NULL, 1, TIMEOUT);

param.FirstCmd = FALSE;

param.KeepCs = FALSE;

Lpspi_Ip_UpdateTransferParam(&MASTER_1, &param);

lpspi_status = Lpspi_Ip_SyncTransmit(&MASTER_1, NULL, spiRxBuffer, 3, TIMEOUT);

Re: s32k312: Lpspi SyncTransmit with NULL Tx buffer

PetrS — Thu, 22 May 2025 07:59:06 GMT

Hi,

yes, this makes sense, as you need to keep CS asserted between.

BR, Petr