Using Nrf51422 as I2C(TWI)

Question

Hello 
 I have an problem using I2C on my custom board which uses an Nrf51422 SOC.
I have an RTC chip connected to it and I have no idea how to use your libraries. 
 The rtc 7 bit slave address is 0xDE. And they have registers which needs to be accessed according to their datasheet.
As per your library for TWI I only see a function such as
nrf_drv_twi_tx(nrf_drv_twi_t const * const p_instance, uint8_t address,uint8_t const * p_data,uint32_t length, bool xfer_pending); which doesn't have registers. 
 If you could please help me how to Read/Write data into the I2C and to its Registers. 
 Regards
Darshan N

RK · Accepted Answer

I don't use it but .. it must be something like this 
 Your slave address is 0xDE, you said, that's the pre-shifted one, Nordic uses just the 7 bits, so it's 0xDE >> 1 or 0x6F. That diagram shows a standard I2C transaction (you should read the spec) so the first byte is the address, shifted, finishing with a '0' which means 'write'. 
 So assuming you want to write 0x12 to the register with address 0x20 and you've set the TWI up already 
 static uint8_t data[2]; // should be a static buffer especially if you're using the callback mode
data[0] = 0x20;
data[1] = 0x12
nrf_drv_twi_tx( &instance, 0x6F, data, 2, xfer_pending );
 
 instance is the instance you set up, xfer_pending depends on what you're doing (ie are you going to do a repeated start to read data back). That writes out the address and two bytes of data to TWI.

Using Nrf51422 as I2C(TWI)

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