COMiX Direct Connection - etxmato/COMiX-HighSpeedDirectConnect GitHub Wiki
The High Speed Direct Connect circuit connects an USB to TTL Serial type adapter cable to the COMiX-35 computer, providing the ability to use a terminal program like TeraTerm to load and save programs between a COMiX-35 and a host computer using the COMiX Direct Connection firmware from this Github repository.
The circuit uses the Q bit output on the CDP1802 in the COMiX-35 computer to transmit data from the COMiX-35 to the host computer and it uses the the EF4 input on the CDP1802 of the COMiX-35 computer to receive data from the host computer.
The circuit to connect the COMiX-35 computer to the USB to TTL Serial Adapter Cable is shown below.
Using the above circuit diagram, you can wire a USB to TTL Serial Adapter plug directly to your COMiX-35 to use with the COMiX Direct Connection firmware. We have tested the High Speed Direct Connect firmware and adapter circuit with several USB to TTL Serial adapter cables and all have worked as expected. Any USB TTL Serial adapter cable (sometimes referred to FTDI USB TTL Serial adapter cables) should work.
Note: The 1N914 diode on the EF4 line is necessary to prevent parasitic current drawn through the Rx on the TTL serial adapter cable. The 1N914 diode on the Q line is added as a precautionary measure as are the two 100 ohm resistors.
If you would rather not wire the USB to TTL Serial Adapter plug directly to your COMiX-35 computer we have designed two versions of a card that plugs into the 44-pin adapter card on the COMiX-35 main board: