aldevan said:look this if it work, schematic and Pin-out of connector, some cable get VCC from serial port from DTR and RTS, if you want use it in microcontroller is better you use independent VCC because you have to use only TX and RX from microcontroller
C-Man said:Even the older Siemens phones operate at 3.6 V (battery voltage).
Simply put a 10K current limiting resistor in series with the TX line from the microcontroller, the phones have diodes that protect from overvoltage inside so there will be no damage ...
best regards
SAWS said:I think I am not clear to make you understood of my problem.
I have a Siemens C55/M55 mobile and its serial data cable. I have send SMS by connecting it directly to PC serial port and using Windoiws HyperTerminal program. I know what AT commands are used for SMS.
My main problem is that now I dont know how to connect AT89C51 with RS232-connector of mobile's serial data cable.
I require
mobile ----------- mcu
RXD | | TXD
TXD | Interface | RXD
GND | | GND
......... ------------- .........
Thanx a lot for your schematic and posts.
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