Move SCB declaration to earlier, so it can be used in other peripheral declarations.
Add I2C peripheral and I2C0 declarations.
Add read support for GPIO port:pin.
Make FPGA JTAG interface pins optionally high-Z, so the FPGA can be programmed with an external programmer.
Add functions to read FPGA done/status signals.
Wrappers for I2C peripheral to provide interface expected by Si5351C-B driver purloined from HackRF.
Add Si5153C driver from HackRF. Someday, this should be its own library?
Add initialization code for I2C peripheral, Si5351C-B, and power supplies.
Ignore many firmware build files.