The MicroUK-101 Project Page

Welcome to the MicroUK-101 PCB Project Page! The MicroUK-101 was designed by Grant Searle. He created a minimal 6502 system based on the UK-101 single-board computer, which itself was based on the Ohio Scientific Superboard II. Grant removed all video output and patched the system to use the serial port for all printing and keyboard input. He breadboarded his design and provided schematics on his web page but did not create a PCB.

This is a project to reproduce Grant's schematics using Kicad, and to design a PCB. I have added a few modifications to make the board a little more flexible.

My PCB Design

The first step was transcribing Grant's schematics into Kicad. I was fairly new at Kicad when I did this in 2016, but learning was one of my goals. I only made a few changes to Grant's design:

• 1) 1 or 2 MHz selectable CPU speed jumper.
• 2) Jumperable IRQ and NMI.
• 3) Barrel Jack for 5V power feed.
• 4) Power switch.
• 5) RS-232 connector.
• 6) TTL Serial header. Can also be used to power the board.

At the time, making PCB's were expensive and some board houses provided incentives to keep the board size to 10cm x 10cm so that was what I was aiming for. I managed to squeeze everthing into 10x10 and successfully hand-routed the board.

Schematics and PCB

Here is the current schematic diagram and PCB:

NOTE: There is an error in Grant's schematic with the MAX232 TX and RX lines. Refer to my schematics for the correction.

Notes

• If you want to power from the TTL serial connector you can omit: Barrel jack, MAX232 + it's capacitors, and the RS-232 connector.
• Set your terminal to 19,200 baud, 8-bit, No-parity, 1 stop bit (19,200 N81).
• To use 2MHz you need a 6502A CPU chip.
• Make sure to populate and jumper the IRQ and NMI lines.
• Use the CAPS LOCK: The power on menu selection and BASIC commands must be in UPPER CASE!

Status

2022-04-18: Working!

I left this board unfinished for a long time, moving on to other projects. I had someone interested in the design and sent them the Kicad files. He made a board and it works!... except for the power connector which is oriented backwards. I have corrected the orientation, updated the board slightly and generated Gerber files.

The design has been released on Github here.

Project History

• 2016-05-19: Initial schematics in Kicad and design mods.
• 2016-09-05: Initial Web page. Fixed RS-232 port gender and re-routed lines.
• 2022-04-18: Status Update!
• 2022-04-19: Corrected design and published to Github.
• 2022-07-11: I finally completed my own board ;-) Updated board pictures and schematics.

Thank-You's

Thanks to Grant Searle for designing the MicroUK-101 and for providing schematics! Grant did all the hard work of designing and debugging the design and patching the firmware for serial operation. Without Grant's hard work none of this would be possible. You can find more info on Grant's MicroUK-101 page.

Thanks to Charles Syms for his interest in my project and taking a chance on my initial 2016 design. Charles made a set of boards and discovered my error with the power connector orientation.

Contact

Page Created: Sep 5/2016. Last updated: July 11/2022, 1:0pm EST

Send comments or feedback to Steve Gray(sjgray@rogers.com)