I was shocked when I saw that none of the Orangutans support JTAG. Seems like a no-brainer to me.
Thanks for the suggestion.
Most of the Orangutans are based on the ATmega48/168/328, which do not have JTAG. It would have been possible to use JTAG on the Orangutan SVP, but in the current design the JTAG lines (PC2-PC5) are being used to control 4 LCD data lines, 3 user pushbuttons, and the green user LED. To support JTAG, we probably would have needed to move those features to other pins, which would probably mean giving up something else (e.g. free analog inputs). Do you have a suggestion for how we could have assigned the pins differently? You can see the current pin assignments on this page:
pololu.com/docs/0J39/7
One of the advantages of AVR ISP is that we have a programmer for $19.95 that works on Windows and Linux and has limited support on Mac OS. I’m not very familiar with the AVR JTAG development tools, but is there a tool that can match that? Do you have a particular AVR JTAG programmer/debugger and IDE that you like to use together?
EDIT 1: I forgot to mention: we did put some thought into the JTAG lines when selecting the pinout for the SVP. We haven’t tried it, but they should be usable if you remove the LCD and don’t press any of the pushbuttons (and the pushbuttons shouldn’t load the lines too much even if you do press them). Let us know if you get it working!
–David
I/O Pins: you could add more pins by using shift registers and/or AVR chips with more pins. To save pins: rig LCD so it only needs one pin to communicate with AVR chip.
USB JTAG Programmer: I have my eye on this one for only $56USA:
microcontrollershop.com/product_ … cts_id=938
Any feedback on whether or not this worked??