Forums / Project Help / PIC16F877 - Siemens C55 - max232 - rs232 SMS Sending - Rickey's World of Microcontrollers & Microprocessors

Discussion in "Project Help" started by galapacos May 25, 2011.

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galapacos

[ Fresher ]

Mon May 30 2011, 12:54 am

i tried that, i change phone's RX and TX still doesnt work.

i connect them like this. i do not connect RX pin of MCU to mobile because i dont use it.

do you think is that right?

ExperimenterUK

Co-Administrator

Mon May 30 2011, 03:12 am

#72

do you think is that right?
galapacos

Yes it looks right.. it should work.

galapacos

[ Fresher ]

Mon May 30 2011, 04:23 am

#73

nothing works. :/

what are differences between max232 and max3232 i look at datasheets but i didnt get the point

galapacos

[ Fresher ]

Mon May 30 2011, 05:53 am

#74

tomorrow i will do my last trying, im going to find a max3232 and tested if it wont work again, i will give up :S

[ Edited Mon May 30 2011, 05:56 am ]

romel_emperado

[ Enthusiast ]

Mon May 30 2011, 06:14 am

#75

dont give up!!! ..

galapacos

[ Fresher ]

Tue May 31 2011, 11:35 pm

#76

how can i connect PIC16f877 - MAX232(max3232) - Siemens c55 to send SMS pls give me advice!!!!

galapacos

[ Fresher ]

Tue May 31 2011, 11:36 pm

#77

i use datacable should i supply datacable?

galapacos

[ Fresher ]

Tue May 31 2011, 11:51 pm

#78

i think in this schematic the right part RX TX and GND for mobile, the left one RS232 part for PC. im connecting microcontroller -> max232 -> rs232 datacable and mobile phone. there is a problem with this.

ExperimenterUK

Co-Administrator

Wed Jun 01 2011, 03:19 am

#79

what are differences between max232 and max3232 i look at datasheets but i didnt get the point
galapacos

The max232 works off 5 volts the max3232 works off 3.3 volts.

i think in this schematic the right part RX TX and GND for mobile, the left one RS232 part for PC. im connecting microcontroller -> max232 -> rs232 datacable and mobile phone. there is a problem with this.
galapacos

The problems are
1.. your phone is intended to work with 3 volt signals and this circuit uses 5 volt signals.
2 The circuit shown gets the power for the 5 volt regulator from pins on the 9 pin connector.
This works if connected to a PC, but not with your micro board because
those pins are not connected.

That said, it should work connected to your PC.
Are you sure the cable you use to connect your micro the your phone
does not contain any extra circuitry ?

[ Edited Wed Jun 01 2011, 03:21 am ]

galapacos

[ Fresher ]

Wed Jun 01 2011, 03:54 am

#80

1. i tried max3232 and supply it 3.3V, i see 3.3 V at mobile phone's pin also tried smaller than 3.3V at pins.

2. "Are you sure the cable you use to connect your micro the your phone
does not contain any extra circuitry ?"

i use datacable and it works at PC so any need extra circuitry for MCU? i do not know.

in that picture interface sheme, RS232 part is going to my datacable and mobile phone and the right side TX,RX and GND goes to microcontroller. Is this connection right?

am i need to external supply datacable 9V or higher?