SIM900d power and data Issues

[assadmahmood]

Greetings EveryBody,
I am using SIM900D interfaced with my laptop with MAX232 in between. I have checked the circuit again and again and each and every thing is fine (no hardware errors).

I also have tested all baud rates (1200 to 115200). but i dont get any thing only I get is garbage data in some symbolic forms or some letters and all that.

What is the default baud rate for sim900d module and what minimum current is required for it?

I giving it a supply of 3.7V and 1A max. is that good for it to operate?


Many thanks for your kind consideration.

 

[embRTS]

I have used POwer Supply for 5V and 2amps It worked successfully Earlier When I used an Adaptor of rating 1 amps it was not working !!

 

[kgshankar1980]

For SIM900 series gsm modules the supply voltage can be - 3.2 V - 4.8V and the current consumption will not go beyond 500mA..Which means a 1Amp power supply or adapter is sufficient enough.

Are you using a development board from SIMCOM or your are using your own designed board which has other circuitry also.

In that case 1Amp may not be sufficient.

And also for any SIMCOM gsm module, the default baud rate is - 115200,8,N,1,NONE...and also comes with ECHO MODE OFF...

Which means that to enable the echo mode ON, type ATE1<ENTER>....

If you are still getting the garbage value after setting the above said BR then pls check your hardware...There should be a problem MAX232 and its circuitry..

 

[embRTS]

Hey You can try to set also with the AT Command for setting Baud Rate

AT+IPR = x   //Where x is Baud Rate like 9600 , etc etc

But I think Problem is in Power Supply only !!

 

[assadmahmood]

I designed my own development board for SIM900D which is given in some datasheets. I ahve tested MAX232 circuitry by interfacing with the microcontroller (ATMEGA8) and it is working perfectly.
My adapter is 12V-1Amp, and after that I am using LM2576-ADJ for voltage range of 3.2 to 3.8V, and I am giving 3.8V to module and MAX232 also getting that same 3.8V.

 

[kgshankar1980]

Then try to use adapter with rating 2Amps...

 

[assadmahmood]

Hello EveryBody,
I am now using power supply of 12V-DC and 12Amp,
Now the issue is when I turned on the GSM module it starts giving garbage on all the baud rates, on 115200 baud it is giving data some thing like this:

ÛÛÛÛÿÛÿÛÿÛÿÛÿÛÿÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÓ'<DC2><NUL><NUL>¶ÛÛÛÛÛÛÛÛÙÛÙÛÙÛûÛûÛûÛÿÛÿÛûÛûÛÛÛÓÛ-<DC2><NUL><NUL><NUL>ºÛÛÛÛÿÛûÛûÛÛÛÛÛÛÛÛÛÛÛÿÛÿÛÿÛûÛûÛóÓ"Š'<NUL><DLE><NUL>¶ÛÛÛÿÛÿÛÿÛûÛûÛÛÛÛÛÛÛÛÛÓÛÓÛÓÛÓÛó'ó'"<DC2><NUL><NUL>²ÿÛÛÛÛÙÛÛÛÛûÛûÛûÛûÛßÛßÛ×Û÷ÛÛÛ÷Û÷'"<DC2><DC2><NUL>²ßÛÛÛÛÛÛÛÛÛÙÛÙÛÙÛûÛÿÛÿÛÿÛÿÛÿÛûÛ÷Û"›<DC1>€<DC2><NUL> þÿÛÛÛÿÛÿÛûÛÛÛÛÛÛÛÛÛÛÙÛÙ"Ù"ÛûÛÛ›››››"'<DLE><NUL><NUL>ÿÛÛÛÛÛÛÙÛûÛÿÛÿÛßÛß"ß"ß"ß"ß"ß'Ó'Ó'"<DC2><NUL><NUL>


where as I am using docklight for RS232 communication, I am getting the above data continuously without giving any single command, I have given AT+IPR=9600,
but didnt get any responce,

What could be the reason, can anybody suggest me

 

[embRTS]

Check with a max232 to uart (usb board) interfaced with PC directly
(("actually I didn't get about the Docklight"))

Try it with Hyper terminal but place that with MAX232 Input Rin and Tout and then it goes to USB via CP2102 IC or FTDI232 IC

i.e the point I am high liting you to use as you said that you have used max232 in your Development Board Design and
have you tested it with MICROCONTROLLER is it working fine ?? I mean how you tested the Working can you explain that further ??

 

[assadmahmood]

Sir actually MAX232 is not in development board, in development board there is only sim900, LM2576-ADJ and its circuitry (1N5822 diode, inductor, capacitors), 2 NPN transistors (2N2222A), AND de-coupling capacitors across Vbat pin and ground of SIM900D and a 3 pin header from with I am getting Rx, Tx and GND to interface it with any other circuit. now the MAX232 board is different it has an IC, 5 capacitors, 1 DB9 connector and the same 3 pin header. thats it!

- - - Updated - - -

What I am suspecting is there is some thing wrong with the SIM900 module and it is malfunctioning (I just doubt) so is there any way to check that either SIM900 is ok or not? before moving to the designing or working phase

 

[embRTS]

If you are not having any Max232 in the Sim900 Circuit that means the RXD- TXD will be as TTL Logic then Connect to any UART to USB Board with Ground Common ,
then Check Don't use via MAX232 ,
Try this !!