Update: We now have a family of T-Boards - for the ATmega328, ATtiny24/44/84 and the ATtiny 25/45/85 controllers.
Refer to "version 0.3" below for a full update, as well a great reason to prototype boards first!
Why the T-Board?
As hobbyists and enthusiasts start hitting the physical constraints of boards like the Arduino, we need take the giant leap into developing our own microcontroller-based boards. The easiest way to transition is onto a breadboard, where we have the flexibility to work with the "raw" microcontroller. Unfortunately, before you've even started adding sensors our actuators, you're knee-deep in a rats-nest of wires.
From this frustration, I developed the T-Board. This is a breadboard-friendly PCB that hosts the microcontroller and its supporting components, while giving the developer flexibility that the fixed-design Arduino-style boards don't. This board is designed for use with the ATmega328, ATtiny24-44-84 and ATtiny25-45-85 range of Atmel microcontrollers.
The T-Board was designed with the following in mind:
- Allow microcontroller prototyping on a breadboard, for the sake of simplicity and speed
- Reduce the number of jumper wires needed to prototype with microcontrollers
- Allow the project to be easily self-powered
- Allow programming through FTDI or ICSP, without using any breadboard points
- 3.3V or 5V selectable: very few boards have this feature, which allows more flexibility with interfacing with external components as well as experimenting wiht lower power usage,
- Choose your crystal: allows you the flexibility to lower power usage for applications where speed isn't critical
Version 0.1 - Toner Transfer
The first version of the T-Board was designed to allow etching by the user. Large tracks and a larger footprint allow for toner-transfer. Some SMD components were included for purposes of space-reduction as well as to provide a gentle challenge to the builder!
Version 0.2 - PCB Prototype
An ICSP header would provide an alternative way to programme the controller, as well as allowing simpler bootloading abilities. Unfortunately a single-sided board does not easily allow for this. As a result I have designed a two-sided PCB that would allow for an ICSP header, as well as a smaller footprint (using narrower tracks and a few more SMD components). The smaller footprint will obscure less of the breadboard holes, and the silkscreen will make designate the pin numbers to make for a simpler user experience. Power has also been made more accessible. The guys at OSHPark have already manufactured the board for me - as soon as I get it in the post I'll post an update.
Version 0.3 - PCB Prototype arrives; family grows
The T-Board328 PCB arrived from OSHPark, and looked great - they clearly use quality fab houses. Unfortunately, I soon discovered that I wasn't that good! As part of the layout process for the self-etched board, I had to mirror the SMD voltage regulators. When I designed the 2-sided board, I of course forgot to "un-mirror" the regulators, with the result that the Vin and GND pins were the wrong way around. I was able to solder the SSOP regulator upside-down (after carefully bending the pins), but not the DPAK. Look at the picture below for the "kludge" workaround. The design is now fixed!
I have also completed two ATtiny boards, which will soon be sent off to the fab. These will nicely compliment the existing ATmega T-Board, particularly on the 2-sided board which has an ICSP header.
For additional information, or to keep updated on the project progress, follow me on twitter.
I have designed this board to meet my needs, but invite comments from others who see additional potential, shortcomings, enhancements.
Bill of Materials
Attached, but not yet linked to supplier part numbers.