The Calypso phones typically all have a serial port @ 3.3V levels on the 2.5mm earphone jack.

Those cables are sometimes called ''T191 unlock cable''.

You can either buy ready-made cables, e.g. at: * USB variant * [http://www.gsmliberty.net/shop/motorola-t191-dataunlock-cable-p-1252.html gsmliberty.net] * [http://www.fonefunshop.co.uk/datacables/motorola.htm fonefunshop.co.uk] * [http://gsmserver.com/cables/Smart-Clip_Cable_for_Compal_Chi_Mei_based_phones.php gsmserver] * [http://shop.sysmocom.de/products/cable-t191-pl2303 sysmocom shop] * RS232 variant, you still need a separate standard USB/RS232 cable * [http://www.cellcorner.com/xshp/unlock-phone-codes/motorola-t190-t191-t193-unlock-data-cable.html cellcorner.com] * USB/RS232 cable * [http://www.tronisoft.com/cat_usbtoserial.php tronisoft.com] (FTDI and Prolific cables)

Or you can build it yourself (detailed instructions can be found on the net, search for "t191 unlock cable" or the like).

• TxD is at the tip of the plug (PC to Device)
• RxD is at the middle contact (Device to PC)
• GND is the outer contact

Hints and Warnings * If you don't use a 3.3V (low voltage TTL, LVCMOS) serial port you can fry your phone! (internally, it connects to the IO-pins of the baseband processor which run at 2.8V). '''Don't connect directly to your PCs serial port (running at +/- 12V!).''' * If your development system is virtualized (runs inside VMware, Virtualbox, Parallels...) the connections can be unreliable (the loader protocol is timing critical). * Your safest bet is a USB cable with a FTDI chip (FTx232) configured for operation at 3.3V connected to a machine running Linux natively. Prolific chips (PL2303) also work, but are far less reliable. * If you want to communicate with the Calypso at baudrates higher than 115200 bps, you'll have to resort to non-standard baudrates. These are also supported best using a FTDI or [wiki:CP210xTutorial CP210x] based USB adapter cable.