new sensor configuration (Melexis MLX90641) - nRF9160

[Vaban]

Hi, I am new to nordic and zephyr and I have a sensor (Melexis - MLX90641) and I would like to test it on a custom board using nRF9160.. I add the sensor into the dts files and I have done all the necessary configuration including I2C and I was able to bind it. now I would like to use the I2C functions to read and write .. but the sensor library is written to work with Mbed OS not zephyr. how can I modify the below functions to work with Zephyr?

I mean the equivalent functions for (i2c.stop , i2c.write, i2c.frequency, i2c.read) for the below example ?

int MLX90641_I2CWrite(uint8_t slaveAddr, uint16_t writeAddress, uint16_t data)
{
uint8_t sa;
int ack = 0;
char cmd[4] = {0,0,0,0};
static uint16_t dataCheck;

sa = (slaveAddr << 1);
cmd[0] = writeAddress >> 8;
cmd[1] = writeAddress & 0x00FF;
cmd[2] = data >> 8;
cmd[3] = data & 0x00FF;

i2c.stop();
wait_us(5);
ack = i2c.write(sa, cmd, 4, 0);

if (ack != 0x00)
{
return -1;
}
i2c.stop();

MLX90641_I2CRead(slaveAddr,writeAddress,1, &dataCheck);

if ( dataCheck != data)
{
return -2;
}

return 0;
}

Melexis MLX90641 library: https://github.com/melexis/mlx90641-library 

[Carl Richard]

Hello! 

Did you check out the I2C API documentation? You have functions for both i2c_write and i2c_read there. You can add a an I2C_MSG_STOP flag to a message to send a STOP after said message, so if you want to set the STOP condition before a transaction you likely have to send an empty message with the I2C_MSG_STOP flag first. The frequency of the I2C interface is configured through Device Tree overlays.

For a demonstration of how the I2C API of Zephyr is used you could check out the I2C Fujitsu FRAM sample and this unofficial I2C scanner sample (which includes overlays).

Best regards,
Carl Richard

[Vaban]

Hi Carl,

Thanks a lot for your explanation, I will check the samples .

[Carl Richard]

My pleasure!

Good luck, and please reach out if you face any issues!

Best regards,
Carl Richard

[Vaban]

Hi Carl,

The zephyr i2c msg.buf accepts only uint_8 input, but in the above function (MLX90641_I2CWrite), the argument (data) - needs to be assigned to msg.buf - is uint16_t

would you please advise on the below if I understood correctly from the examples:

struct i2c_msg msg;

uint8_t buf[4] = {0x0, 0x0, 0x0, 0x0};

//sa = (slaveAddr << 1);

buf[0] = writeAddress >> 8;

buf[1] = writeAddress & 0x00FF;

buf[2] = data >> 8;

buf[3] = data & 0x00FF;

msg.buf = buf;                   // Herę is the issue 

msg.len = 4;

msg.flags = I2C_MSG_WRITE | I2C_MSG_STOP;

k_msleep(500);

i2c_transfer(i2c_dev, &msg, 1,0x33);

[Carl Richard]

Hi again!

From what I can see in the MLX90641 datasheet it uses 8-bit addressing, so I believe it should be fine to stick with that. Please report back if it doesn't work!

Best regards,
Carl Richard