RE: how to initialize spi_cfg and switch the slave when multiple slaves on a same spi bus?

scottwan — Fri, 03 Dec 2021 09:02:02 GMT

Hi Simon,

I use DEVICE_DT_GET(node_id) can get the specific spi device and get the correct specific data which is the device chip id 0xd1 and 0xd2 as in picture below by call spi_transceive() in sensor_channel_get() function.

There still have a problem, the sensor driver initiation function get the same chip id but sensor_channel_get function can get different chip id:

main():

#include <zephyr.h>
#include <sys/printk.h>
#include <drivers/sensor.h>

/* 1000 msec = 1 sec */
#define SLEEP_TIME_MS   1000
#define ads129xr0 DT_NODELABEL(ads129xr0)
#define ads129xr1 DT_NODELABEL(ads129xr1)

void main(void)
{
	struct sensor_value value;
	// const struct device *dev = DEVICE_DT_GET_ANY(ti_ads129xr);
	const struct device *ads129xr0 = DEVICE_DT_GET(ads129xr0);
	const struct device *ads129xr1 = DEVICE_DT_GET(ads129xr1);

	if (!device_is_ready(ads129xr0)) {
		printk("Device %s is not ready\n", ads129xr0->name);
		return;
	}
	if (!device_is_ready(ads129xr1)) {
		printk("Device %s is not ready\n", ads129xr1->name);
		return;
	}

	sensor_channel_get(ads129xr0, SENSOR_CHAN_ALL, &value);
	sensor_channel_get(ads129xr1, SENSOR_CHAN_ALL, &value);

	// printk("ads129xr volt %d.%d\r\n", value.val1, value.val2);

	printk("Hello World! %s\n", CONFIG_BOARD);
	
	while (1) {
		// printk("Hello World! %s\n", CONFIG_BOARD);
		k_msleep(SLEEP_TIME_MS);
	}
}

I think the problem raised because at the beginning, both device CS are in active status during the first device call spi_tranceive(), so uncertain result received, the result maybe from the first device but also probably from the other one depends who's signal arrive MCU first.

RE: how to initialize spi_cfg and switch the slave when multiple slaves on a same spi bus?

Simon — Wed, 01 Dec 2021 22:10:38 GMT

[quote user=""]Does SPI_CONFIG_DT_INST(inst, operation_, delay_) can be used for multiple slaves on the same spi bus? and how to select or active the specific slave when call spi_transceive()?[/quote]

I looked into the documentation, and it does not seem like using the Devicetree instance number is the way to go if you want to get a specific node (slave). Check out the comments given in Option 1: create devices using instance numbers and API Reference-->Devicetree-->Devicetree API:

"However, they only work when devicetree nodes for your driver’s compatible are all equivalent, and you do not need to be able to distinguish between them."

"instance numbers in no way reflect any numbering scheme that might exist in SoC documentation, node labels or unit addresses, or properties of the /aliases node (use DT_NODELABEL() or DT_ALIAS() for those)

there is no general guarantee that the same node will have the same instance number between builds, even if you are building the same application again in the same build directory"

I would recommend you to go for Option 2: create devices using node labels instead, then you will be able to get a specific node (slave).

Best regards,

Simon