Hello everyone!
I am trying to figure out how SPI drivers for Bosch bme280 sensor work... I would like to somehow recycle them to write my own SPI drivers for another device (an adc from Texas Instruments).
I am currently looking at "bme280_spi.c" (you can find it in /zephyr/drivers/sensor/bme280). I really don't get what is the purpose of the "buf" pointer passed as an input argument to the function bme280_reg_read_spi. Moreover, rx_buf[1].buf = &buf[1]: what does that mean?
Can you please me help me articulating a little bit more about the purpose of the "buf" pointer? And do you know why rx_buf has size 2?
Here's the code fragment I am struggling with:
static int bme280_reg_read_spi(const union bme280_bus *bus, uint8_t start, uint8_t *buf, int size) {
uint8_t addr;
const struct spi_buf tx_buf = {
.buf = &addr,
.len = 1
};
const struct spi_buf_set tx = {
.buffers = &tx_buf,
.count = 1
};
struct spi_buf rx_buf[2];
const struct spi_buf_set rx = {
.buffers = rx_buf,
.count = ARRAY_SIZE(rx_buf)
};
int i;
rx_buf[0].buf = NULL;
rx_buf[0].len = 1;
rx_buf[1].len = 1;
for (i = 0; i < size; i++) {
int ret;
addr = (start + i) | 0x80;
rx_buf[1].buf = &buf[i];
ret = spi_transceive_dt(&bus->spi, &tx, &rx);
if (ret) {
LOG_DBG("spi_transceive FAIL %d\n", ret);
return ret;
}
}
return 0;
}
Thanks to everyone in advance!
