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Old 11-08-2008, 10:28   #1 (permalink)
bgreat
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Arrow How to find rx and tx

FIND OUT RX & TX BY FOLLOWING METHODS FOR CHINA MOBILES
It is tasted and also you can test it.

1 step is, we need to find GND from phone.

2 step is, we should power on phone (operation with dead phone:
phone must be 100% dead by software)and take multimater put it to voltage.

3 multimeter (-) line put it GND and with (+) line check each connectors
, and usually Tx= 1.8v or 2.8v and Rx=1.7v or 2.7v
(it will be change by processor but strongly 1.7v or 2.8v not 3v or 4v)
This way is too easy and you will save a more time.

For example!
You have got new brand China miracle phone with USB cable. It has got
12 pin. You must find (Infinity team give good Idea 1.2.3 punkts):
1) GND usually it has got 2 GND. (now we have got 10 pins)
2) We will uncheck USB + and USB- (VSS) just with checking by USB cable (now we have 8 pins)
3) By USB cable we also uncheck V bat+, ac adaptor + polarization (now we have 7 pins)
4) Now from this 7 pins you will find 1 or 3 not used pins (last operation we have 3 or 6 pins to find Rx Tx signals)
5) Now at last operation you should use good multimeter just to find Rx Tx with 1.7v-2.7v or 1.8v-2.8v
6) WHEN PHONE IS POWERD OFF TX AND GND WITH MULTIMETER MAKING BEEEEEP
(DIOD TEST OPERATION), WHEN PHONE POWERED ON IT WILL SHOW LIKE DIOD
RESISTANS 600-700 OHM BETWIN TX AND GND.

I think I have give for every body more informationís. Just try to
find. If you find 2-3 phone signals and you will be profi mobile Tx and
Rx signals finder.
Some times you will not find with this method some phones, but why we have forum?


This instruction will helpful for people who works in GSM repairing industry minimum 3-5 years.


How to find pinout for unknown model:

In most cases you need to know Gnd, Rx, Tx pins for flash/unlock
operations. What do do if you don't have cable or you have new phone
model:

1. find Gnd pin (it's required step, you can't continue until
you will know Gnd pin location)

2. find Charge pins (it's optional step, just to save your
time during future research)

3. find +Battery pins (it's optional step, just to save your time
during future research)

4. connect cable Gnd to phone Gnd
5. try to connect cable Rx/Tx wires to all phone contacts one by
one (except Gnd, Charge, +Battery pins) and try to read flash from phone
6. if flash read procedure can start this means that pinout found Ok
and you can make other operations

Note about "Chinese models": a lot of different phones with the same
name exist on market (as well as many different name phones with the
same pinouts), so, if you see in our "cable selector" wrong pinout for
"Chinese models"it's good idea to find correct pinout acording to above
instruction and send found pinout information with full text from phone
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