Hi,
The protocol for doing a register read for the LMP90100 is as follows:
A common mistake is to use 0x90 as the 'Instruction Byte 1' in the 'Transaction 1 - URA Setup' section of the Register Read protocol, since the data sheet shows the '0x90: Read Address' option here.
However, the 'Transaction 1' is to set up the URA, so we are actually WRITING to the Upper Register Address, so we need to have '0x10' as the 'Instruction Byte 1' of 'Transaction 1'.
The '0x90' Instruction byte is never really used in the first transaction of the register read protocol.
Instead, 'Transaction 2' is where we specify we are doing a Register Read, by having a '1' as the first bit of 'Instruction Byte 2':
The following is an example doing two Register Reads of the ADC_DONE (Address 0x18) register, following the Register Read Protocol, to check if ADC data is ready:
The following is an example of doing a Register Read of three registers in the same SPI frame starting at the 0x1A register address and ending at the 0x1C register address, to retrieve the ADC data:
Best Regards,
Angel
