WiringPi I2C library to get 16bit value

[Milliways]

I have used the WiringPi I2C library to perform simple byte transfers between a Raspberry Pi and an Arduino (using function wiringPiI2CRead).

I want to get the Arduino to return 16bit word values, but am at somewhat of a loss.

Arduino has `Wire.write(data, length)` which I could use; WiringPi has `int wiringPiI2CReadReg16 (int fd, int reg)` but I am somewhat confused by the `reg`. There seems to be no definition of device registers.

I have looked at the WiringPi code and read http://www.mjmwired.net/kernel/Document ... -interface

Can anyone clarify and/or show some sample code.

[BAStumm]

I had a similar problem where I needed to read 4 bytes over i2c.

read(fd, temp, 4);

[jamesm]

WiringPi has `int wiringPiI2CReadReg16 (int fd, int reg)` but I am somewhat confused by the `reg`.

reg is the data address to read from. This corresponds to the parameter after the chip-address when you call i2cget,

Code: Select all

i2cget -y 1 0x48 0x0 w

As an example, I'm trying to read temperature from the LM75 which has a device address of 0x48, register address of 0x0, so the call would be

Code: Select all

int fd = wiringPiI2CSetup (0x48);
int data = wiringPiI2CReadReg16 (fd, 0x0);