First debugging of Pico code for Virtual 2315 Cartridge Facility

SERIAL DEBUGGER LINK CONNECTED, CODE IN PICO AND NEW DISK IMAGE ON CARD

I had the modified RK-05 Emulator hardware set up in my lab with a serial USB connection placed on the debug UART pins. A microSD card with a valid 1130 disk image was inserted in the card reader. The Pico had been reprogrammed with my Pico code that I need to test. 

The only part not yet updated was the FPGA, as I was waiting for the Lattice programmer that I apparently need to load its proprietary bitstream into the FPGA chip over the JTAG interface. I hoped that I could get some preliminary testing done before I have the programmer which should arrive by Wednesday. 

POWER UP WITH CARD INSERTED BUT LOAD SWITCH LEFT OFF

I was expecting the box to power up with a drive number (0) displayed in the small OLED screen, although there could have been some issues reported by debugging print statements such as a mismatch of FPGA version number. 

However, the OLED remained blank. All I saw on the serial terminal was the first print showing that the emulator was starting up. I didn't see the messages that should occur while it initializes the SPI links to the SD card reader as well as starts up the FPGA. 

To determine where exactly it was stalling, hopefully pointing me at the fault, I put in quite a few more diagnostic print statements. They showed me that it got mostly through the initialization of the GPIO (I/O pins that drive LEDs and other functions from the Pico) but seemed to be locked up after a couple of SPI calls to the FPGA. 

I am diving in with more detailed diagnostic information, although this could simply be a consequence of the mismatched FPGA code. It isn't immediately obvious to me how it would stall but I will find out.