I wanted a pocket computer that I could build myself to learn through-hole soldering and get a simple, basic computer. There were a lot of projects out there, but I needed a kit ready to mount, without having to look for components around the world.

The core component is the Atmega328. The keyboard is serial with tactile momentary switches and the display is a SPI OLED type with the common SH1106 driver. A toggle switch and LED complete the Cobalt 3 (giving a name was the coolest part of the job).

I put everything together in the design of a simple PCB and I used an Arduino IDE to compile the O.S. in C++ language. The O.S. can be loaded through a UART serial interface.

The O.S. is composed of 3 parts: one to show data on the display (data output), one to manage the keyboard (data input), and last but not least, one to elaborate the Basic Language instructions (data elaboration).

Color model list

• Blue Shadow: the default model, the opaque Blue one with header, keys and led red
• Dark Winter: the White model with blue header, black keys and white led
• Red Dragon: [currently sold out]
• Black Shadow: [currently sold out]

Components list

• 1 × pcb
• 1 × Oled Display 128x64 SPI 7 pins
• 1 × AAA battery holder
• 1 × led
• 40 × tactile momentary switches
• 1 × 220 Ohm resistor
• 1 × 1 K Ohm resistor
• 1 × 33 K Ohm resistor
• 1 × AAA Li-Ion battery 3.7v 350-600 mAh
• 1 × Crystal 16.000 MHz
• 2 × 22pf capacitor
• 1 × 104nf capacitor
• 1 × atmega328p
• 1 × socket 28 pin narrow
• 1 × header 6 pin
• 1 × toggle switch 3 pin

The Story

I started soldering little electronics kits, not without some difficulties. When I thought I was ready to level up, I found out it was too complicated for me to solder and get working a complete computer kit I can buy on a website like Tindie. There were a lot of projects out there, but I needed a kit ready to mount, without having to look for components around the world.

At that stage the learning curve was too steep. I needed a loophole. So came the idea for my project, creating something that I can also provide to other hobbyists as a simple kit with instruction.

What was the best way? The idea was to start with most familiar electronic components for my objective.

Inspiration

I tried not to modify the software I used and to maintain in its original state, but I had to make several changes to make all parts work together. Credits go to all developers of Tiny Basic, of Arduino libraries, of Tiny Lisp Computer, of Keymap library, SPI and SH1106 drivers, etc. Thanks to all.

I learned a lot making this project, and I think many newbies as me would enjoy soldering a kit like this and learn something new.

Docs available on GitHub :

• Cobalt Basic v1 user manual
• Cobalt 3 keyboard guide
• Cobalt 3 assembly guide