OsmocomBB

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:

 * [https://www.akku-king.net/_py_Handyzubehoer-Datenkabel-USB-Motorola-USB-Datenkabel-fuer-Motorola-T191-C113-C113a-C114-C115-C115i-C116-C117-C118-C119-C121-C122-C123-C136-C139-C140-C155-C156/a-20104991/ akku-king.net]

 * [http://www.gsmliberty.net/shop/motorola-t191-dataunlock-cable-p-1252.html]

 * Some stores also sell a RS232 variant, you still need a separate standard USB/RS232 cable

  * [http://www.dealextreme.com/details.dx/sku.14664 dealextreme.com] RS232, not USB variant

  * [http://www.handy-style.de/index/cat190/2130]

  * [http://www.cellcorner.com/xshp/unlock-phone-codes/motorola-t190-t191-t193-unlock-data-cable.html]

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- or Prolific chip (FTx232, PL2303) configured for operation at 3.3V connected to a machine running Linux natively.