32-BITS SPI READ

[gianmarcod]

Good morning everyone,

I need to read a 32-bits register using 8-bits communication (I have already set up spi configuration structure to communicate over 8-bits transactions).

Can you please tell me how I should size data structures required by spi_read function in this particular situation?

These are the data structures I am talking about:

const struct spi_buf rx_buf = {

   .buf = 

   .len = 

}

const struct spi_buf_set rx = {

   .buffers =

   .count = 

}

How would you set them up?

There should also be some data buffer linked to the .buf entry of rx_buf if I am not mistaken. Which size should it have?

Thanks in advance.

Gianmarco

[Marte Myrvold]

Hi Gianmarco,

For 32-bit (or 4 byte) you can do the following:

static uint8_t rx_buffer[4];

const struct spi_buf rx_buf = {
   .buf = rx_buffer,
   .len = sizeof(rx_buffer)
}

const struct spi_buf_set rx = {
   .buffers = &rx_buf,
   .count = ARRAY_SIZE(rx_buf)
}

Best regards,

Marte

[gianmarcod]

Hi Marte,

Thanks for your feedback. I usually set .count=1, which is probably wrong.

Setting count=ARRAY_SIZE(rx_buf) triggers the error you can see in the picture below.

Do you think that it may be due to the fact that spi_buf has size 1?

Regards,

Gianmarco

[Marte Myrvold]

Hi Gianmarco,

Most likely, yes. You can use .count=1 instead.

Best regards,

Marte