I attended your Geiger Counter workshop at CCC. The thing is happily beeping away, so I got myself Adafruit's FTDI Friend and am trying to get data off the counter via serial, but not having much luck. I checked with a multimeter that the electrical connection between the serial port and microcontroller pins is ok. FTDI Friend's RX/TX leds aren't indicating any traffic. The FTDI Friend is set for 3V signal level.
Basically I am just wondering whether there's any known issue, and if not, are there any simple first steps (beyond the multimeter) that would help towards debugging? I don't have a scope myself, but perhaps this is the business reason to buy one?