Ok, I've been getting lost in this one for a while, and I'm sure it shouldn't be this difficult to find. Basically, I'm trying to attach my Pi to a device that demands a ±12v RS232 connection. I've already tried a cheap USB to serial adapter, and that turned out to be TTL levels. No go there. I know that I could put something together to run off the GPIO pins with appropriate parts (perhaps the Sparkfun RS232 Shifter kit), but I'll admit that my electronics knowledge is somewhat weak, and my soldering is worse! Additionally, this approach would require a new case for my Pi. However, if this is the best way to do it, I'm willing to try.
For me, the ideal solution would be a simple USB to RS232 ±12v adapter with the converter board in the USB end of the cable. Why the USB end of the cable? Because the device has an RJ14 (6P4C) socket, and if it's that way round, I can replace the DB9 with the right plug to remove the need for an extra inline adapter cable. If anyone knows where I can find such a cable, I'd love to hear of it. Failing that, any recommendations for USB to DB9 RS232 adapter that is confirmed to work with a Pi and provides a ±12v signal would be a great help.
For those interested, I'm trying to connect to a Celestron Nexstar SLT handset. I've already got the Pi Camera and eyepiece working nicely, with camera control running over ad-hoc wifi to tablet/smartphone. So far, everything's working nicely, but the next step in the project is controlling the telescope mount from the same software. Custom software, work in progress. The setup is often assembled in the dark, hence I'm trying to minimize adapter cables.
Any suggestions and or/advice is welcome!
Thanks in advance, P.
edit: After having submitted this, I spotted the link from RoddyJoff's post below, Add a 9-pin Serial Port to your Raspberry Pi in 10 Minutes. It looks promising, but it's not entirely clear whether it's providing 5v or 12v output. Anyone more knowledgeable than me able to comment?