easy -> When change register address i2c during read operation

Question

My question is very easy (I think). Let's say I want to read a register, where a result is stored by a sensor.

At which moment do I need to specify the register I want to read? After the slave address as data? http://imgur.com/EhO6d6m

I don't think so. Because If I previously did a write operation in register 0x1234. And afterwards just do a read (without specifying anything). I will read data from register 0x1234.

Where/when do I need to specify the address of the new register I want to read?

If someone has an answer please let it be known. Thank you

Answer 1

Generally, you have to specify the register you want to read from (if it's not already set) by using a write!

Issue

STA
SLA+W
REGISTER
rSTA
SLA+R
DATA
STO

That's the most common format. Other less common variants include:

STA
SLA+W
READ_REGISTER_ADDRESS
REGISTER
rSTA
SLA+R
DATA
STO

Ie some devices only let you manipulate a pointer to the next data register that is read.

Some devices don't have multiple registers, so you always read from the same register.