Hello techies! 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.
Cheers.
hi,
please read the wiki : http://bb.osmocom.org/trac/wiki/CalypsoSerialCable -> only use 3.3V
kevin
On 04.02.2011 00:47, labad jala wrote:
Hello techies! 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.
Cheers.
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.
Regards, Harald
I made this interface and it is 100% working!
http://baseband-devel.722152.n3.nabble.com/file/n2965249/Motorola_T191_unloc...
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Please double check if your cable's output is 3.3v... this circuit could fry your phone. The output of MAX232 should not exceed 3.3v
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With a 7805 and max232, it looks like it is probably 5v (the circuit is using the R2OUT/T2IN pins, which are Vcc, so 5v). A MAX3232 with something like a LM2940-3.3 would probably be a *much* better option, and give you real 3.3v.
Loki
On Fri, May 20, 2011 at 7:43 AM, wpatan wpatan@gmail.com wrote:
Please double check if your cable's output is 3.3v... this circuit could fry your phone. The output of MAX232 should not exceed 3.3v
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these are my voltage measurements
http://baseband-devel.722152.n3.nabble.com/file/n2979519/Motorola_T191_unloc...
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what serial port are you using? usb-serial? a laptop one?
you are not frying your mobile only because you are lucky: your com port fails to deliver the 12~15v standard to the rs232 and delivers 5v instead
so the 7805 regulator fails to deliver 5v because it's a linear regulator with a high drop out (internal voltage loss- it is designed to work at at least 6 or 7v ) plus the diodes voltage drop and it's delivering 3.4v
if your connect that cable to a good com port, it will drive the calypso at 5v and it will fry it. right now is delivering 2.5v on tx, and it seems that's just enough to drive the calypso serial
TL;DR: get a usb->ttl3.3v cable and forget this one
also, did anyone tried attaching a phone to a 5v cable to see if it really dies?
2011/5/24 Roy roytiberius@gmail.com
these are my voltage measurements
http://baseband-devel.722152.n3.nabble.com/file/n2979519/Motorola_T191_unloc...
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Hi,
you are not frying your mobile only because you are lucky: your com port fails to deliver the 12~15v standard to the rs232 and delivers 5v instead
so the 7805 regulator fails to deliver 5v because it's a linear regulator with a high drop out (internal voltage loss- it is designed to work at at least 6 or 7v ) plus the diodes voltage drop and it's delivering 3.4v
Yup exactly.
if your connect that cable to a good com port, it will drive the calypso at 5v and it will fry it. right now is delivering 2.5v on tx, and it seems that's just enough to drive the calypso serial
Actually his cable is delivery the 3.4 V.
The 2.5V comes from the calypso because its serial port _is_ 2.5V and not 3.3V. We use 3.3V converters because they are more common and work fine, but it's still overdriving the calypso.
also, did anyone tried attaching a phone to a 5v cable to see if it really dies?
It might not die right away, the ESD diodes will take some of it at first ... but for how long is the question. It also depends on the impedance of the driver, if you have a 1k resistor on the path, it would help I guess. But there is also the issue of the 2.5V from the calypso needs to be detected as 1 by a 5V cable.
Cheers,
Sylvain
Ok thank you for your comments I've inserted a zener diode between the ground and Rx pin to reduce the tension.
http://baseband-devel.722152.n3.nabble.com/file/n2983706/Motorola_T191_unloc...
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Just now I tested this interface with a Prolific USB cable and works well
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baseband-devel@lists.osmocom.org
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Harald Welte -
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Lokkju Brennr -
n0p [Luis Bernal] -
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tsaitgaist -
wpatan