I got two modems (dev boards) Siemens TC35 and SIM900A and I cannot get them to send sms.
From the research (AT response) it seems that somehow sim cards will not register to network.
I bought three sim cards from different networks currently operating in my location.
Commands to GSM module:
Code:
AT
OK
AT+CREG?
+CREG: 1,0
OK
of course further AT didn't work also.....
Code:
AT+CMGF=1
OK
AT+CMGS="+385xxxxxxxxx"
> test (CTRL-Z)
+CMS ERROR: 302
All SIM cards have their pin security check disabled. All cards have been inserted into phone, tested for a call and tested to send SMS to another phone. Also all of them all full of credit.
TC35 is cursed somehow.
It didn't work until I've plugged it without sim card and powered on. Then while working I've inserted pin and restarted module and it worked, is it some capacitor or god knows what... no one knows.