Arduino GPRS shield only showing first character of SMS via serial monitor (AT+CMGR Not working)

0
votes

I am interfacing a seeedstudio GPRS shield for my arduino UNO via the serial monitor Arduino window, and some writing directly echo'd to the tty (I am using Linux)

I am able to interface with it properly in the regards of sending text messages and even receiving them, however when I run the command to read the messages (Knowing it's ID) I am only returned the first character of the message, as such:

+CMGR: "REC READ","MYPHONENUMBERHERE","","13/10/15,21:45:44-40"
H

The full message was "Hmmm" and the only thing showing is the "H"

The exact command run is as follows:

AT+CMGR=3

Also, interestingly enough, when I run

AT+CMGL="ALL"

I do appear to get every message

+CMGL: 2,"REC READ","+1xxxxxxxxxx","","13/10/15,21:35:51-40"
+CMGL: 3,"REC READ","+1xxxxxxxxxx","","13/10/15,21:45:44-40"
+CMGL: 4,"REC READ","+1xxxxxxxxxx","","13/10/16,06:08:24-40"

ALSO, the SIM was obtained through AT&T's GoPhone service, and is properly activated with the SIM900 Module on the GPRS shield, and as mentioned, can send text messages fine, but getting them to show up correctly is broken.

The shield I am using is found here: www.seeedstudio.com/wiki/GPRS_Shield_V1.0

2
serial-portsmsarduinogsmgprs

2 Answers

3
votes

I had the same issue and finally found there was a maximum receive buffer size of 64 set in the SoftwareSerial.h include file.

I found the following line:

#define _SS_MAX_RX_BUFF 64 // RX buffer size

and changed it to:

#define _SS_MAX_RX_BUFF 128 // RX buffer size

Then I could see the whole message.

The include file SoftwareSerial.h can be found in the Arduino/libraries/SoftwareSerial directory. For Arduino 1.0.5, which I am running under Windows.

On my MAC (which is running Arduino 1.5.4) I found the file: SoftwareSerial_Class.h contains the old SoftwareSerial.h code. Haven't tested this one yet!

Post back and let me know how you go.

0
votes

I change it to: 

#define _SS_MAX_RX_BUFF 256 // RX buffer size

because the message could be 160 character long.

!! NOTE the number must has only this values: 64, 128, 256, 512(?) and so !!