I made this interface and it is 100% working! http://baseband-devel.722152.n3.nabble.com/file/n2965249/Motorola_T191_unlo… -- View this message in context: http://baseband-devel.722152.n3.nabble.com/hmm-sorry-data-cable-question-tp… Sent from the baseband-devel mailing list archive at Nabble.com.

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(a)gmail.com> wrote:

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(a)gmail.com>

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_unlo… -- View this message in context: http://baseband-devel.722152.n3.nabble.com/hmm-sorry-data-cable-question-tp… Sent from the baseband-devel mailing list archive at Nabble.com.