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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?

Make sure your baud rate is set to 9600 8-N-1. And try swapping the TX/RX lines, just in case the FTDI friend is backwards compared to a real FTDI cable (I doubt this, but you never know...) Also, make sure you have fresh batteries, maybe the FTDI friend isn't able to go down to 2V logic levels???

There aren't any known issues - I would recommend picking up a real FTDI 3.3V cable and testing with that.

Checking in again now that I am home. Did you get it working?