AVR Programmer 1.0

Just sent off DORKBOT_1_0 to Laen (yeah, we reuse version numbers around here). Interesting changes:

  • Added an FTDI-cable-compatible header. This means the board has the hardware capability to do USB-TTL serial I/O, and it should be able to program Arduino Pros and other barebones Arduinos.
  • Dropped the two ground pins on the VCC/3.35.0 header. The original idea was to make it possible for that header to act as a small power source, but it turned out to be a confusing opportunity for short circuits.
  • Brought out the 4MHz emergency clock source that Dean’s AVRISP source code already provides.
  • Brought out XCK. In theory, with a couple external resistors connecting TXO and RXI to form the DATA line, TPI/PDI programming will be possible.
  • Brought out two GPIO pins. They’re buffered so they’re output-only.
  • Switched from the ‘125 to a ‘241 to accommodate the extra outs.
  • Dropped the redundant pullup resistor on /RESET.
  • Added a solder jumper for /HWB so it’s easier to get the board into bootloader mode.
  • Stopped sending MISO through the buffer. This was a curious design decision for USBtinyISP, and it also made ISP of the board itself more difficult than it should have been.
  • Switched to larger-than-microscopic labels. Maybe they’ll be readable this time!