Reading external sensor using I2C on nrf9160dk

[Jagruti]

Hello,

I want to read external accelerometer on nrf9160dk using I2C. But when I connect SDA and SCL pins of sensor to nrf91, there is no output.

The Code is:

#include <nrf9160.h>
#include <zephyr.h>
#include <misc/printk.h>
#include <i2c.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>

#define I2C_ACCEL_READ_ADDR   60

struct device * i2c_accel;
u8_t I2C_BUFFER[35];


void init_accelerometer(){
    i2c_accel = device_get_binding("I2C_2");
    if (!i2c_accel) {
		printk("error\r\n");
	} 
    i2c_configure(i2c_accel, I2C_SPEED_SET(I2C_SPEED_FAST));

}


void main(void)
{
        printk("Start I2C comminication\r\n");
        init_accelerometer();

	while (1) {

                i2c_read(i2c_accel, I2C_BUFFER, 29, I2C_ACCEL_READ_ADDR);

                printk("I2C_BUFFER = %s\n", I2C_BUFFER);
	}
}

When I don't connect sensor to nrf91, then continuously it prints "I2C_BUFFER ="

When I connect the sensor, everything stops and when I again remove the pins it prints "I2C_BUFFER ="

What I am doing wrong? How to read these sensors value?

Thank you

[Turbo J]

i2c_read() has a return value - you might want to check that for communication errors...

Also, I2C_BUFFER is not a string. The binary data might just have a zero in the first place...

[Sigurd]

Hi,

Here is some code that you can test to see if you get a response from the sensor. If there is an ACK for the address, it prints the address it found.

main.c

#include <nrf9160.h>
#include <zephyr.h>
#include <misc/printk.h>
#include <i2c.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>


#include <gpio.h>

#define I2C_ACCEL_WRITE_ADDR 0x32
#define I2C_ACCEL_READ_ADDR 0x75

struct device * i2c_accel;
uint8_t WhoAmI = 0u;


static struct device  *led_port;

#ifdef CONFIG_SOC_NRF9160
#define I2C_DEV "I2C_3"
#else
#define I2C_DEV "I2C_1"
#endif


void main(void)
{
	struct device *i2c_dev;
	
	k_sleep(500);

	printk("Starting i2c scanner...\n");

	i2c_dev = device_get_binding(I2C_DEV);
	if (!i2c_dev) {
		printk("I2C: Device driver not found.\n");
		return;
	}
	
	uint8_t error = 0u;
	
	i2c_configure(i2c_dev, I2C_SPEED_SET(I2C_SPEED_STANDARD));


	printk("Value of NRF_TWIM3_NS->PSEL.SCL: %ld \n",NRF_TWIM3_NS->PSEL.SCL);
	printk("Value of NRF_TWIM3_NS->PSEL.SDA: %ld \n",NRF_TWIM3_NS->PSEL.SDA);
	printk("Value of NRF_TWIM3_NS->FREQUENCY: %ld \n",NRF_TWIM3_NS->FREQUENCY);
	printk("26738688 -> 100k\n");
	
	
	
	for (u8_t i = 4; i <= 0x77; i++) {
		struct i2c_msg msgs[1];
		u8_t dst = 1;

		/* Send the address to read from */
		msgs[0].buf = &dst;
		msgs[0].len = 1U;
		msgs[0].flags = I2C_MSG_WRITE | I2C_MSG_STOP;
		
		error = i2c_transfer(i2c_dev, &msgs[0], 1, i);
		if (error == 0) {
			printk("0x%2x FOUND\n", i);
		}
		else {
			//printk("error %d \n", error);
		}
		
		
	}
	

	
	
}

nrf9160_pca10090ns.overlay

&i2c3 {
	status = "ok";
	compatible = "nordic,nrf-twim";
	sda-pin = < 12 >;
	scl-pin = < 11 >;
    clock-frequency = <I2C_BITRATE_STANDARD>;  
};

prj.conf

#CONFIG_SERIAL=y
#CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_I2C=y
CONFIG_I2C_NRFX=y
CONFIG_I2C_3=y
CONFIG_I2C_3_NRF_TWIM=y

CONFIG_NEWLIB_LIBC=y


#CONFIG_LOG=y
#CONFIG_I2C_LOG_LEVEL_DBG=y
#CONFIG_LOG_BACKEND_UART=y
#CONFIG_I2C_INIT_PRIORITY=60

[Jagruti]

Hi,

I tested the above code with accelerometer.

This is the Output:

***** Booting Zephyr OS build v1.14.99-ncs3-snapshot2-2647-gd6e67554cfeb *****
Starting i2c scanner...
Value of NRF_TWIM3_NS->PSEL.SCL: 11 
Value of NRF_TWIM3_NS->PSEL.SDA: 12 
Value of NRF_TWIM3_NS->FREQUENCY: 26738688 
26738688 -> 100k
error 251 
error 251 
0x 6 FOUND
error 251 
error 251 

Why that error is coming? The problem is with nrf91 or at accelerometer side? The address is 60 and it is showing 6.

Is there anything else I have to configure on nrf91?

[Jagruti]

I tested the above same code again and now the address is 0x69. But when I try to read at this address there is nothing. And the address is 60 so why it is showing 69. I am not getting this.

[Sigurd]

What accelerometer sensor are you using ?