Lattice Radiant: How do I use the RGB pins on iCE40UltraPlus as GPIO?
The SB_IO_OD primitive is only available for the iCECube2 SW, you will have to use BB_OD as this is the equivalent primitive for the opendrain buffer in Radiant. Note that for Radiant, BB_OD is automatically mapped in the netlist/design whenever you use the opendrain pins of the device (39, 40, 41), which makes these pins function as an ordinary GPIO.
1) Whenever we add the RGB primitive in our design, it is guaranteed that the tool will utilize the OB_RGB (this buffer is used when RGB Function is used):
1.1) Using Port X for RGB primitive causes the 2 other outputs (y and z) to be used as RGB pin functions instead of GPIO pins (as shown it uses the OB for RGB).