How to read two byte register address using arduino wire library

Question

I want to read a register 0x012A from the device I2C address 0x0A, the value stored in the register is two bytes, If the register address is one byte i can use Wire.requestFrom and give the register address and how many bytes i want to read since here register address itself 2 bytes i'am bit confused . can any one help in this regard.

Answer 1

i can use Wire.requestFrom and give the register address and how many bytes i want to read

So you give it 2 to ask for 2 bytes.

Then you combine them. How you do that depends on what the bytes represent. If the first is the upper byte and the second the lower byte of a 16 bit value then you would:

uint8_t b1 = Wire.read();
uint8_t b2 = Wire.read();

uint16_t val = (b1 << 8) | b2;

If it's the other way around then just swap the variables in the combining section.

However if the values are some other arrangement (I saw something recently that had two registers with a 12 bit value with overlapping bits) you will have to combine it in the way that is required for that specific arrangement.