I'm trying to record to an N900 from an external line (actually a bat detector!).

I've soldered some connectors to the correct 3.5mm 4 way plug - a stereo socket for headphones, and a mono lead for input.

Unfortunately, most of the time, the N900 doesn't detect that there are headphones and a microphone attached. The kernel output (dmesg) suggests that it detects the plug being inserted but the headphone icon doesn't appear.

I wondered if this was caused by some other setting, so I reset the device from Settings/Restore, and for a brief period, I had it working. I could record sound (using Recaller) from the line out of a PC or (frequency divided) from the bat detector, as intended.

However, after unplugging the socket, and plugging it back in, it no longer works, or only works very occasionally when I plug it into the PC line out (with some high volume sound playing).

I can get the headphone icon to appear by shorting the microphone to ground, but that of course doesn't enable the microphone.

I also have a similar problem with the AV out - I wanted to connect the audio out to an amplifier, and this only works if I short the video lead signal to ground.

Anyone got any ideas? I haven't got an official headset to try it with, unfortunately, as I didn't get one in the box.

I managed to solve this by saving the alsa settings with a working headset plugged in, and creating a shell script to restore these using alsactl. I can now click on an icon to enable the headset/microphone/headphones, regardless of whether it has been detected or not - works quite well.