Hi ckshivaram,
...first of all, thanks a lot for your soon reply!
...I have resolved the garbage problem!...It was a mistake with my reception buffer pointers, and the long response commnands got garbage...
Now when I power on, i get the following message!:
RDY
+CPIN: NOT INSERTED
+CFUN: 1
I think that now is initializating ok!...
However it appears that the SIM900 can't access to the sim card...even if I put the card or don't it...
I have made the design that the HD recommends:
- On clk, data and reset I have put 22 ohm resistors.
- On data pin of SIM900 I have put 20pf capacitor.
- I have realised that I forgot the 100nF capacitor on VDD pin of the sim card.
Could be that the reason why the SIM900 don't identify any SIM card even if it is inserted?...
Thanks a lot in advance!...
The power suply I designed is based on BQ24070 Li-Ion Charguer, power suply from Texas Instruments. I get the same result using a 800maH battery or using a 5V 2A wall charguer.
In the theory, powering the system with a fully chargued mobile battery, and with a pcb with good vcc and gnd planes, and some tantalum and eletrolythic capacitors near the VBAT pins should start up ok!...
Regards,
Ignacio