In order to program the ATMega8 included with the Asuro Robot Kit I have designed two AVR Target Boards. Initially I had both in one, but I couldn’t fit both on the one veroboard. This target board is designed to program most 40 pin, 28 pin, 20 pin and 8 pin AVR 8-bit microcontrollers, for example ATMega162, ATMega328, ATMega128, ATTiny2313, ATTiny13, etc. I included a 2×3 ISP header so it will work with most new AVR ISP Programmers (for example adafruit’s USBTinyISP), but for those wanting a 2×5 header it should be a simple modification.
Version Differences
There are a few differences between the two target boards:
- The large target board is designed for 40 and 28 pin AVRs (the ATMega’s), while the small one is for the 20 and 8 pin AVRs (the ATTiny’s).
- The large board has one ZIF socket for each size of AVR, while the small one has one ZIF socket for both sizes (with a size jumper to select the size, more details below)
- The large target board has two (selectable) clock sources available; a crystal (I used an 8MHz one) and an ATTiny13 providing a clock for boards with bad clock fuse settings. The small target board has the ability to add a clock source in (XTAL1 and XTAL2 lines have been designed in, however no clock source has been designed).
Clock Source
There are three clocking options with the large board:
- No clock: Remove all jumper shunts
- The ATTiny clock: Insert a jumper shunt into the right jumper
- The crystal clock: Insert two jumper shunts, one into the center jumper and the other on the left.
Setting up the ATTiny13 clock
To setup the ATTiny13 clock you need to unprogram the CKDIV8 fuse on the ATTiny13 (for an excellent fuse calculator visit http://www.engbedded.com/fusecalc/) and burn a program that will oscillate PortB4 of the ATTiny. I have written a basic program, you can download the source file, clock.S, and compile yourself with an AVR ASM programmer like AVRA (you will need the ATTiny13 include file, tn13def.inc) or simply download the precompiled clock.hex. You should now have an ATTiny13 creating a square wave at ~1.4MHz, perfect for our needs.
Chip Select (between 8 and 20 pin ATTiny’s)
In order to combine the 8 and 20 pin sockets into one I have added a setting jumper under the socket; to program an 8 pin AVR (for example an ATTiny13) place the jumper shunt on the left and on the right to program a 20 pin AVR (for example the ATTiny2313).
Notes, Schematics and Veroboard layout
- Pin one for the AVR ISP headers and the AVR microcontroller sockets is always the bottom left one (when the socket is oriented to be under the ISP header).
- The target board in the images is missing the 10k resistor between pin 1 of the ATTiny13 clock and VCC, I would recommend installing it.
Here are the schematics (also in SCH, for EAGLE) and the veroboard layout (these are for the all-in-one version):
Also, images of the undersides:
