www.mycpu.eu (C) 2021 by Dennis Kuschel 

Use your old    as serial Terminal!

Recycle your old Commodore 64 and use it as serial Terminal for your microcontroller projects, your Linux box or your MyCPU or MyNOR! This page describes an expansion cartridge for the C64 that turns your C64 into an universal ANSI compatible RS232 Terminal.   Features:
  • ANSI compatible Terminal, 7 Bit character set
  • 80x24 character screen on the Commodore 64 (!!)
  • all common escape sequences are supported
  • supports coloured text (still experimental)
  • serial speed up to 115200 baud with handshake
  • uses a standard 16C550 UART chip with 16 byte FIFO
  • plug and play: single cartridge, no floppy disk required
  • a hexadecimal display mode for incomming data is implemented
  • all configuration data is permanently stored in an EEPROM
  • the project is fully open source

Download the EAGLE-files: eagle-files.zip
Download the cartridge board layout as pdf: layout.pdf
Download the cartridge gerber files: term-gerber.zip
Download the source-code: termsoftware.zip

C64 with installed terminal cartridge
This is the prototype of the cartridge:

this is the terminal cartridge
closeup of installed terminal cartridge

Jörg Reinhard has designed a housing for the PCB.
You can download his STL files for 3D-printing here:

The housing is available in two variants. One without cover if you use sockets for all ICs, and one with cover, if only the UART is socketed.

Jörg can be contacted through his website.

Picture of the optional housing for the cartridge

Schematic of the cartridge:
Schematic of the terminal cartridge. Click here to download a high resolution image.

If you want to build this cartridge you will find everything you need on this page. I recommend you to use the gerber-files of the PCB to let the board be manufactured at some pool based factory like JLCPCB. But you can also download the PCB Layout if you whish to etch the board yourself.

At the right side you see the placeplan of the board. Please use sockets for all the integrated circuits. At least the UART chip IC1 must be fitted with a socket, otherwise you won't be able to place the transistor T1. Please follow the placing order in blue numbers, otherwise you won't be able to solder the red pads at the top side of the board (this does not apply if you use a manufactured PCB). Start with placeing the sockets for the integrated circuits, then continue with the resistors and capacitors. Fit the remaining transistor, oscillator and the SUB-D connector.

Download the software archive, and extract the file rom.bin. Use an EPROM programming device to program the file rom.bin into the EPROM IC2. Note that the upper area of the EPROM remains unused.

List of required components:

 Pieces  Value Components
7 100n C1 - C3, C10 - C13  
6 2,2µF Tantalum    C4 - C9
1 16C550 IC1
1 27C256 IC2
1 74LS74 IC3
1 74LS138 IC4
1 74LS04 IC5
1 MAX232 IC6
1 24C16 IC7
1 1,8432MHz QG1
2 2,2 K R1, R2
1 BS170 T1
1 SUBD9, male X1

Hint: You can use the UART cartridge also for other applications. Please remove the EPROM and cut the /EXROM -wire near to the expansion board connector. The UART can be accessed through the memory area $DE00-$DEFF. If you whish to uses this "universal UART cartridge" as terminal you can still load the file terminal.prg from disk (the file is included in the softare package).
Component Placeplan. Click to enlarge. Component Placeplan

C64 Terminal Screen, 80x24 characters, monochrome This is a close-up of the C64 Terminal Screen. As you can see the 80x24 character screen (in monochrome mode) is easy to read. The screenshot shows the boot sequence of the MyCPU

If you have questions please email me: dennis_k@freenet.de

 www.mycpu.eu (C) 2021 by Dennis Kuschel