Is there a schematic out there somewhere for a dependable and CHEAP USB to Serial converter? I have a radio that needs a serial input, but the laptop has only USB. Speed isn't an issue, 4800 baud is enough and it has to be bidirectional.
Caution - that's USB to TTL-serial, not USB-to-RS-232. Most radios intended for hookup to a PC have an RS-232 port, and the Bub won't work with those (wrong voltage, reversed polarity).
I'd suggest searching eBay for a commercial USB-to-serial adapter whcih uses the Prolific PL-2303 chip - it has decent Windows and Linux drivers. Example: auction 260829278362 is for one such, $7.59 "Buy it now" with free shipping included (I know nothing about this particular seller, but there are probably many others selling equivalent adapters with this chipset).
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
Which is US$14.00 plus US$4.00 for shipping, or a total of US$18.00 each, shipped in the US.
It has similar features and is US$12.99 plus US$3.85 shipping for US$16.84 in the US.
Since the OP requested schematics, the schematics for the above product is available at that link, too.
Also, FTDI provides sample schematics:
Look for those regarding the FT232R. They also include docs on the drivers and a bunch of app notes, as well.
Or the op could just order one of these:
if the OP can tolerate non-RS232 voltages (no level shifter on the board) then get it for US$4.30 with free shipping. Just don't use the two microcontrollers, the crystal, or the header supplies. Provides a cable with a microB at one end and a board with a TUSB3410. I've used that one up to 9600 bps without troubles. Driver may be required from TI, though. Schematics also available for that, as well, at TI's web site.
FWIW: Several Local Ham Radio Operators have had issues with the Prolific converters. I believe the problem is the matter of getting the correct driver in each case and I have ordered a couple of the Prolific devices from different sources to test my theory. The FTDI HID->RS232 converters seem to be idiot proof.
When a Ham Radio Operator is in pursuit of an elusive contact he (or She) has the mind set of a Beagle Hound on a rabbit trail! There is no such thing as patience!
The problem is that here are bad Chinese clones of the Prolific chip around. If you get a genuine Prolific, you'll be fine. If you get a Chinese knockoff, it will probably work with Linux and XP, but on Win7, you'll have all sorts of problems. There are hacked drivers around, but even with those, it may not work right.
The safe bet, of course, is to avoid Prolific and go to Silicon Labs or FTDI in stead. FTDI have the FT232R, which is factory programmed with device ID and serial number, so it's ideal for hobbyists.
Thanks to all. I found a PL-2303 based cable that I got a year no questions asked refund guarantee on. I got it home and plugged it in. On the port selection menu on the radio (Ten Tec rx320) there was now a /dev/USB0 next to the /dev/ttySx selections. Magic. No drivers needed.
The Linux Kernel handled everything automatically.