hmm, sorry, data cable question

Harald Welte laforge at
Fri Feb 4 07:50:31 UTC 2011

On Fri, Feb 04, 2011 at 12:47:50AM +0100, labad jala wrote:

> I am new to the list and I acquired a c139. I'd like to buy a rs232/jack
> 2,5mm named t191 flash (and not unlock) cable. They look 100% the same (even
> stickers). Is this important? I understand that I have also to use a
> rs232/usb adapter. The one I have (U232P9 with link/tx/rx leds) gives +/-9,4
> v. So my concern is to not fry the Moto..Any advise welcome.

if you put a usb/rs232 converter and then a rs232/2.5mm cable behind each
other, there should be no problem, at least not voltage-wise.  The usb/rs232
converter cable with DB-9 will up-convert to +/- 9V, and the T191 cable
with DB-9 will then down-convert again to 3.3V

In case of any doubt, simply use a multimeter to verify.  RS323 is low-active,
i.e. in idle state the lines are at their highest voltage.

- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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