We use a lot of our ATmegaXX8 “business card” breakout boards for the ATmega168 microcontroller. We also still wire up a lot of minimal target boards to use the ATtiny2313 microcontroller, so here’s the missing piece: A simple breakout board for the ATtiny2313.
Like the original card, our design goals for this project were (1) to make a printed circuit board version of the minimalist target board for the microcontroller, encompassing a place for the chip and a connection to the 6-pin ISP header, (2) to make a minimal and inexpensive circuit board platform that you could use to deploy a single AVR somewhere with without much fuss, (3) to encompass the capacity of a breakout board, giving extra holes to tap into each pin of the AVR and provide labels for every pin, (4) to fit in some small amount of flexible prototyping space, (5) to make it all fit into a neat business-card form factor, and (6) to release it as an open-source project.
The circuit board is 2″ x 3.5″ (Standard business card size of course). The bottom side silkscreen on this has our store information; if you’re making your own version of this you can obviously replace that with your own contact information.
On the top side of the board, dominating the playing field, is the place for the microcontroller, which can sit in a standard DIP socket. We’ve also made the holes big enough to accommodate a ZIF socket for easy programming.
All 20 pins of the microcontroller are labeled with their main functions. Besides the pins that actually connect to the ATtiny2313, there are four access holes connected to every pin of the microcontroller. In the upper left, there are input connections for power (typically 3-5 V) and ground, which are routed to a couple of other locations on the board. In the upper right is a place for the 6-pin ISP header with pin 1 marked. In the lower right is a place to add an optional crystal oscillator with its two capacitors, or a 3-pin ceramic resonator.
Finally, mounting holes are provided in each corner for 6-32 size screws, located with centers 1/8″ x 1/8″ from each corner.
Using the board
Since this is effectively an implementation of the minimalist target board, you don’t need much to run one of these. Ideally, the board, plus a chip, plus the 6-pin ISP header and a programming interface (at least once). To run on its own it will need and external power source as well, and AVRs like this can run (depending on load) from a 3V lithium coin cell or from a more powerful source. We usually run ours on external battery boxes with switches, either with two or three AA cells. This board has a location for a power jack onboard, that takes a center-positive DC voltage up to 5 V.
Under the hood
This is a very straightforward breakout board, so there shouldn’t be any surprises in the layout. We’ve made the ground traces nice and fat, and routed power and ground connections to several useful places on the board.
To get started working with this design on your own, we have a single ZIP file, available for download here, (492 kB .ZIP file) which contains the full schematic diagram (PDF format), a PDF of the PCB layout showing the individual circuit board layers broken out individually with crop marks– making this layout a cinch even for home-etched circuit boards, and the original PCB layout file. (The circuit board was designed in gEDA PCB— free, open-source printed circuit board software.) We are releasing the design for this board under open source licenses and under a creative commons license as well.
Or, take the easy way out and get a kit here. :)
Want to talk about it? That’s what the forums are for.
Got projects based on this board to show off? We’d love to see your pictures in the Evil Mad Science Auxiliary.
Version 1.1 of this project is now available. Please see here for the details.