I am trying to read messages from sim900a as they get received and filter them to get the required messages. But most of the times the message are getting delayed (10-60 min). I need the delay to be as minimum as possible.
The AT commands I am using to initialize the connection are:
ATZ
AT+CMGF=1
AT+CSDH=1
AT+CLTS=1
AT+CPMS="SM","SM","SM"
AT+CNMI=1,1,0,0,0
AT+CSCS=\"GSM\"
AT+CSAS
And to read messages I am using
AT+CMGL=\"ALL\"
I have used different and same carrier sims but the delay largely remains same (slightly reduced in case of same carriers). I used the sims in two mobile phones and the messages are received almost instantly.