Delay between read and write SPI operation

RE: Delay between read and write SPI operation

Naeem Maroof — Wed, 07 Aug 2024 14:08:44 GMT

You are reading 2 bytes, right? If there should come 2 actual bytes on MISO from the sensor then you can configure buffers like this and test again: (please review the code and modify accordingly if you are receiving different amount of data)

uint8_t regs[3];
regs[0] = reg_addr;
regs[1] = 0xFF;
regs[2] = 0xFF;
uint8_t readbuf[3];		//3 is used as you are to receive 2 bytes
                        //1st byte received will be dummy byte

struct spi_buf 	tx_spi_buf 		    = {.buf = (void *)&regs, .len = sizeof(regs)};
struct spi_buf_set tx_spi_buf_set	= {.buffers = &tx_spi_buf, .count = 1};
struct spi_buf 	rx_spi_bufs		    = {.buf = readbuf, .len = sizeof(regs)};
struct spi_buf_set rx_spi_buffer_set	= {.buffers = &rx_spi_bufs, .count = 1};

//use spi-transceive or spi-transceive-dt as per your overall code setup
err = spi_transceive_dt(&spispec, &tx_spi_buf_set, &rx_spi_buffer_set);
if (err < 0) {
	LOG_ERR("spi_transceive_dt() failed, err: %d", err);
	return err;
}

RE: Delay between read and write SPI operation

Mahdibs — Wed, 07 Aug 2024 07:43:52 GMT

    
    const struct spi_buf tx_buf = {
		.buf = &reg_addr,
		.len = 1,
	};
	const struct spi_buf_set tx = {
		.buffers = &tx_buf,
		.count = 1,
	};
    struct spi_buf rx_buf = {
        .buf = reg_data,
        .len = 2,
	};

	const struct spi_buf_set rx = {
		.buffers = &rx_buf,
		.count = 1,
	};

RE: Delay between read and write SPI operation

Naeem Maroof — Tue, 06 Aug 2024 17:03:00 GMT

How you have configured the buffers?

RE: Delay between read and write SPI operation

Mahdibs — Tue, 06 Aug 2024 12:38:46 GMT

Thank you for your reply.

I have tried with spi transceive and I got a wrong rx data but the timing is better:

rc |= spi_transceive(spi_spec->bus, &spi_spec->config, &tx, &rx);

I also tried 2 spi transceive like the following, and I got the same result as separate write and read which is obvious since the spi write and read are based on the spi transceive.

    rc |= spi_transceive(spi_spec->bus, &spi_spec->config, &tx, NULL);
    rc |= spi_transceive(spi_spec->bus, &spi_spec->config, NULL, &rx);

I'm trying to implement nrfx in my project, I'll post update once done.

Thanks

RE: Delay between read and write SPI operation

Naeem Maroof — Tue, 06 Aug 2024 08:15:40 GMT

Have you tried with spi transceive function rather than a separate write and read?

Otherwise, you could use nrfx as the delay might be unavoidable due to zephyr layer.