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vogelchr, 02/19/2016 10:48 PM
Added hints and warnings.


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:

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.
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