open-source-silicon.dev

Silly question… when we taped out we used the lowest 8 GPIO pins for an output, of those we need only the lowest 3 to get a useful value (either `0x4` or `0x3`). Do I understand correctly that pins 1-4 are used for the HKSPI? What would happen if I tried to configure them for our output? and how could I go about doing that?

Figured out that after flashing the storage we don’t actually need the HKSPI, so we configured the pins to `reg_mprj_io_1  = GPIO_MODE_USER_STD_OUTPUT;` etc and we were able to read out the values we wanted. Downside is that because we took the pins away from the HKSPI, whenever we wanted to reflash the program, we had to do <https://open-source-silicon.slack.com/archives/C05KBE2DJFJ/p1690294903190499|the complicated reset procedure mentioned earlier in this channel>. Still interested to know, though, if there were any hidden pitfalls to this approach. Happy to learn more.

<@U05GC63A2JG>:  The only pitfall is that when using those pins as output, you will have to run a script that we have in the caravel_board repository called "hkstop.py" which forces the FTDI to set the pins connected to those GPIOs to type input.  I believe some of those pins may continue to have a resistive pull on them even when they are configured as inputs on the FTDI.