I am looking to transmit a small package (4-16 bytes) between two MSP microcontrollers (MSP430FR6*** -> EXP430FR413*) in a device, so the distance between them is fairly short (<10cm).
Both of them have eUSCI modules that support UART, I2C and SPI -- so I guess those are my options.
I got the EXP430FR4133 devboard and am testing things out.
My first try was a high baud rate UART (as I have worked with that before) but it looks like the MCU does not have enough time to wake up from LPM3/4 and receive the data properly at speeds above 19200 (and that is with SMCLK at 16MHz).
Transmitting 4 bytes consumes about 1.4uA on the host, which is quite a lot.
From the datasheet SPI and I2C seem to have the same power draw /MHz.
Any recommendations on the choice between SPI/I2C or any other advice on how to save power?