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[SOLVED] SIM900 HELP me! Basic commands work but Extended doesn't and return ERORR

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Newbie level 3
May 3, 2011
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Hi to all
I bought a SIM900 with developing board.
all Basic commands such as ATE , ATZ , AT&F , AT&V are working and return OK in HyperTerminal window
, but Extended commands for example AT+CMGF=1 doesnt work and return ERORR
pls help me

1. check if you use correct power supply.
2. Check if you have a proper antenna
3. check if you have a valid SIM card without password protected.
4. check AT+CSQ? you should not get 99,99. you should get some values other than 99,99
5. check at+CFUN?

Hi to everyone!,

I'm also working with a SIM900 module...I turn it on via powerkey and it appear that is ok, but I get those errors:

1) If I put AT command it responds OK, also when for example I put ATE0 command. All appears to go OK!

2) I have configured the baudrate to 9600bps, so when I start the system and try to read the RDY indication I get that plus an ammount of garbage!...
I turn on the module using powerkey, and i get this frame:
Hexadecimal bytes: [0d 0a 52 44 59 0d 0a 0d 0a 2b 63 2b 0c 0c 63 57 3a 20 00 2c 30 0d 0a 0d 0a 4f 4b 0d 0a 05 c4 9f 9b 70 83 73 96 f3 b7 78 1d e8 5e 11 be 0e c9 cd 23 0d 0d 0a 4f 4b 0d 0a 4d 8f 54 b6 15 78 96 b1 e4 73 59 c2 50 49 4e 3a 20 4e 4f 54 20 49 4e 53 45 52 54 45 44 0d 0a 0d 0a 2b 43 46 55 4e 3a 20 31 0d 0a ]

Char bytes:

aW: ,0


+CFUN: 1

It's a lot of garbage!....anyone know the reason of that?...

3) Other command like AT+CPIN? returns directly "ERROR"

...the module responds the same whe I use the simcard and when i don't use it...
...I didn't view with the oscilloscope any voltage drop on vdd...I use 4.4 vdd voltage thought a BQ24070 from texas instruments...
...I view with the oscilloscope 64ms on and 800ms off signal...
... The module responds okto the commands A, AT adothers after the reception of the garbage....

Any idea?...Thanks alot in advance

...thanks a lot in adavance

Hi dears,

I faced this problem these days and i found the solution,

The problem was in my serial port of my PC, try to re-install the port and configure it in a wright way then test your SIM900 board.

Moreover, I found this link it is very useful to test your GSM

It is very good :grin::grin:

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