Nice job by hogemark on work so far; this capability really needs to be native to Energia. My goal is to use MSP430F5529 USCI_B1 as an I2c slave and USCI_B0 as a SPI master. I have code based on pull request 590 working fine as I2C master, but doesn't succeed as I2C slave. Guessing this is something in the guts of the function as the onRequest() function isn't dependent on which module is being used. Probably an issue with interrupts not enabled for the module. I'm going to dig in twi.c and post results back here. Any suggestions are appreciated.