Bring up the PCBs - Githubissues

thejpster / monotron

A simple 8-bit home computer style application for the TI Tiva-C Launchpad

Apache License 2.0

191 stars 9 forks source link

Bring up the PCBs #55

Open thejpster opened 5 years ago

thejpster commented 5 years ago

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

thejpster commented 5 years ago

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 commented 5 years ago

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

thejpster commented 5 years ago

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 commented 5 years ago

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

thejpster commented 5 years ago

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 commented 5 years ago

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 commented 5 years ago

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 commented 5 years ago

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 commented 5 years ago

Tested RTC. Can read and write registers ok.