ATmega32 interfacing with sim300z GSM modem

[mabn.007]

I am able to communicate my microcontroller to hyperterminal but I am not able to send AT commands directly to gsm modem through my microcontroller plz help me

 

[fouwad]

hi im having an issue with my controller that it sends all characters on hyperterminal correctly but when the characters with ASCII having continuous 0s are not displayed for eg: ';'=48=00110000, '\n' =10=00001010
what could be the problem
plz reply

 

[mabn.007]

give delays in between the characters

 

[fouwad]

hey some1 reply

 

[karthi_keyan]

hey

it ll surely reply
1.check ur PC comport first,set ur controller baudrate with modems default firmware baud rate.
2.if it is a evaluation board it will work with straight cable RS232(DB9).
3.if it is ur own design check status pin whether its turned on or not because if u type anything when it has a proper communication it will reply each and every character.
4.connect ur controller directly to PC and check the out of controller.

regards
karthikeyan

 

[fouwad]

the microcontroller communicate with hyperterminal absolutely fine but when sim300z is connected with atmega32 it doesnot respond
plz tel a way through which they can communicate

 

[GSM Man]

the microcontroller communicate with hyperterminal absolutely fine but when sim300z is connected with atmega32 it doesnot respond
plz tel a way through which they can communicate

You may have the transmit and receive lines switched.

 

[fouwad]

i tried to join them by straight if it were the problem the issue wud hav had resolved
the problem is somewhr els
plz help

Added after 4 minutes:

plz plz plz tel me what changes shud i make if i hav a db9 female connector instead of db9 male
plz do reply

data cable have max232 circuit within the port. and it get power from DB-9 PC.

i dont know what voltage and from which pins of PC's DB-9 the data cable get the power.

You have to supply these voltage to DB-9 connector
pin 7 DB9 (RTS) -9 Volt
pin 4 DB9 (DTR) +9 Volt
pin 5 DB9 (GND)

But be careful that the following pins
pin 2 DB9 (RXD)
pin 3 DB9 (TXD)
has a RS232 Voltage level, that's >+5 Volt as logic level '0' and <-5 Volt as logic level '1', you can't connect this pin to micro controller's TXD pin and RXD pin directly, it may burn out that pins!

once i connected direct C55 's TX,RX & grd with CELL phone the at commands works but other day it doesn't work

Without the above voltage supplies, the data cable doesn't works!

some body told me that u must use MAX232 is to interface and use data cable.

Yes, its true!

Another connection is like this:

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