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

[Jagruti]

Thank you so much. Your solution is working.

But there is other problem. I receive some data then it shows "*** buffer overflow detected ***: terminated". When I run same program on nRF52840 with NRFX TWIS drivers there is no problem.

How can I avoid RX buffer overflow?

Output:

***** Booting Zephyr OS build v1.14.99-ncs3-snapshot2-2647-gd6e67554cfeb *****
Starting TWIS program!
Data = ,,,,,,,0,
Data = ,,,,,,,0,
Data = ,,,,,,,0,
Data = ,,,,,,,0,
*** buffer overflow detected ***: terminated
exit

[Turbo J]

My crystal ball says: Don't use msg buffer on the stack with fire-and-forget (read event based) TWIS functions.

[Jagruti]

I did not understand what you are trying to say. Can you please explain. I am still getting the same error. 

[Sigurd]

If you are getting NRFX_TWIS_EVT_READ_REQ event, you need to call nrfx_twis_tx_prepare(). And try to change

nrfx_twis_rx_prepare(&m_twis, I2C_BUFFER, size); 

to

nrfx_twis_rx_prepare(&m_twis, I2C_BUFFER, sizeof(I2C_BUFFER)); 

[Captain CK]

From where did you find this "i2c.h" library