Bring up the PCBs

[thejpster]

• Receive PCBs
• Check power in
• Check VGA out
• Check audio
• Check SD/MMC
• Check joystick
• Check RS-232
• Check MIDI Through
• Check MIDI In
• Check MIDI Out
• Check RTC
• Check Atmega runs OK (need test firmware)
• Check Atmega comms
• Check Atmega connection to LPT port
• Check Atmega connection to PS/2 keyboard port
• Check Atmega connection to PS/2 mouse port

[thejpster]

VGA is fine. https://twitter.com/therealjpster/status/1087475018542563334
SDMMC needs 47k pull-ups to 3.3v on CS, MOSI, MISO and SCK otherwise the card isn't detected.
It also needs a current limiting resistor or a big capacitor on Vcc, as inserting a card causes the CPU to reboot - it's probably tripping the brown-out circuit? https://twitter.com/therealjpster/status/1087475302249517057

[thejpster]

Audio is fine. Joystick is fine too, but my joystick is broken :(

[thejpster]

UART TX for RS-232 and UART TX for MIDI looks OK. Need to check input with a loopback cable and some a UART test function.

[thejpster]

PS/2 connector footprints are backwards. Connectors need to be fitted to reverse of PCB.

[thejpster]

UART RTS/CTS was wrong in software. Fixed, and tested by sending > 16 chars to Monotron using screen /dev/ttyS4 115200,crtscts. Noted that RTS line went high when 8 chars received (FIFO half-full).

[thejpster]

Now I have a null-modem cable, I've checked the MAX3232 circuit - seems fine. RS-232 voltages are +6V/-6V. Was able to dump a large text file in using Bray Terminal and it respected the RTS from the Monotron and avoided UART FIFO overflow.

[thejpster]

Tested MIDI In with my Drum synth and valid MIDI bytes appeared OK. Connected MIDI Out to MIDI In with a cable (so, a loopback test) and any bytes I sent were received OK.

[thejpster]

Updated schematic to rev 0.8.0:

• Added SD activity LED
• Connected INIT to the MCU via the two spare hex inverters
• Moved SELPRIN to pin INIT was using
• PC6 (former SELPRIN) as Atmel RESET
• Added ISP header for Atmel programming
• Added SMT microSD footprint
• Added 47k SD pull-ups

I can probably add the LPT wiring changes onto the two 0.7.0 boards I've built. Will need to cut two tracks to the LPT port and some bodge wires.

[thejpster]

Tested RTC. Can read and write registers ok.