SIM900D RXD/TXD communication problem

[Kopi_]

Hi everyone,
I have a problem. I have been using SIM900D GSM module but the serial communication don't working.
The module are running and it is connecting on the network.
I am measuring on the pin 4 (TXD) 2,7V.
What is a problem?

 

[Fe(II)man]

which module are you using to be specific?

 

[Kopi_]

I am using SIM900D modul. I am looking for the problem of this module.

 

[asimlink]

Hello Kopi,
Please follow following instructions to resolve / debug your SIM900 problem.

1. You should first wire your SIM900 module through RS232 transceiver to PC.
2. Turn On SIM900 module
3. On PC side run any rs232 terminal and issue AT commands
3. For example when you type "AT" you should get "OK" response
This way you can test if your sim900 is running. Please remember all of your commands delivered to SIM900 must be terminated with a CR character. Otherwise SIM900 does not acts on the command received.
Regards

 

[Kopi_]

Hi asimlink,
Thanks for your quickly answer.
I have not RS232 terminal. I am sending for you a pictures of my develop.
I checked on the TXD pin on the pictur. I measured 2,87V on the pin(4).
So I have not serial communication.
What is problem?
Best regards

 

[Kopi_]

Hi,
I finded my problem.
My problem was level of voltage. Now running serial kommunikation.
Thanks!