Burst on ECSPI2 on i.MX8M Mini EVK

[frk]

Hello,

I'm trying to use ecspi2 on the i.MX8M Mini EVK using spidev.

I've followed the hint of the following topic to set spidev :

https://community.nxp.com/thread/502230

My main question is the following one :

Why the chip select toggle between each byte sent whereas I send 255 byte each time?

I use the following simple code :

static void transfer(int fd, uint8_t const *tx, uint8_t const *rx, size_t len)
{
    int ret;
    struct spi_ioc_transfer tr = {
        .tx_buf = (unsigned long)tx,
        .rx_buf = (unsigned long)rx,
        .len = len,
        .delay_usecs = delay,
        .speed_hz = speed,
        .bits_per_word = bits,
    };

    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
    if (ret < 1)
        pabort("can't send spi message");
}

...

uint8_t default_tx[255] ;
uint8_t default_rx[ARRAY_SIZE(default_tx)] = { 0, };

for (i = 0; i < SIZESPI; i++)
            default_tx[i] = i;
transfer(fd, default_tx, default_rx, sizeof(default_tx));

Using a scope, I see that the chip select timing is pretty strict but its value change 255 times.

Best regards,

Frederic

[igorpadykov]

Hi Frederic

one can check parameter BURST_LENGTH in ECSPIx_CONREG register

described in sect.10.1.5.3 Control Register (ECSPIx_CONREG)

i.MX 8M Mini Applications Processor Reference Manual

Also one can find ecspi examples with burst=8 in SDK_EVK-MIMX8M Mini

available on Welcome | MCUXpresso SDK Builder 

Best regards
igor
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[frk]

Thanks for this quick reply.

Do you know where the ECSPIx_CONREG register can be found in Linux kernel?

Best regards,

Frederic.

[igorpadykov]

ecspi registers can be found in Chapter 2 Memory Map  Reference Manual

memtool can be used for reading registers

memtool\test - imx-test - i.MX Driver Test Application Software 

Best regards
igor