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SIM900A - how to check if SMS received

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hithesh123

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Does the SIM900A, change any of the pin status or give any indication when an SMS message has been received?

What's the simplest way to check without using AT commands.
 
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RXD pin have receive data available but you have not logic status like 0 or 1 I think
 

Does the SIM900A, change any of the pin status or give any indication when an SMS message has been received?
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I always use AT commands, but the Ring Indicator (RI) pin is able to also indicate sms, if I can recall correctly.
 

Send AT Command "AT+CNMI=2,1" Once before entering while(1). Then when there is new SMS GSM sends AT response "AT+CMTI: "SM", x" where x is SMS index in SIM. Compare this response with the response string stored in ROM and if response match then issue "AT+CMGR=x\r" command and check for response "\r\nOK\r\n". If response received is OK then extract the actual SMS message and take action depending upon the SMS message.
 

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