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Author Topic: SIM900 GSM/GPRS - downloading jpg to module  (Read 1911 times)
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Hello,

I bought one of these http://imall.iteadstudio.com/im120417009.html for a project I'm working on. I'm trying to send a jpg saved on an SD card via MMS. I am able to send SMS text messages fine, but when it comes to downloading the image to the GSM module, I'm having the biggest difficulties.

From looking at the MMS example in the manual on page 25, it says to do AT+CMMSDOWN. Then it says that when the module prints "CONNECT" to the serial monitor, that means that its ready to receive information on the UART. I have not figured out a way to make it read data. Perhaps I'm now writing to the UART right or something... I don't know. But eventually, the module exceeds the specified time limit and prints "ERROR".

http://www.mt-system.ru/sites/default/files/docs/documents/sim900_mms_at%20command%20manual_v1.01.pdf

Here is what I'm working with now to attempt to write data to the module.

  File dataFile = SD.open("datalog.txt");

  // if the file is available, write to it:
  if (dataFile) {
    while (dataFile.available()) {
      Serial.write(dataFile.read());
    }
    dataFile.close();
  } 
  // if the file isn't open, pop up an error:
  else {
    Serial.println("error opening datalog.txt");
  }

The microcontroller that I'm using is an Arduino Uno.

If somebody can offer some help, it would be greatly appreciate it.



Thanks for your time!
Ted
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Somone help! Please!! D':
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I'm not familiar with that module, but it looks as if it has a uart and I assume that's the one that is expecting to receive your data. Does it have a uart? Is the Arduino connected to it and using the correct serial settings? Is the Arduino receiving "CONNECT" at the right time? The code seems to be sending the data over the Arduino's hardware serial port, so unless you have connected the Rx/Tx lines to the GPRS module's Tx/Rx lines, I wouldn't expect that to work. (This would mean you can't also use the hardware serial to talk to the PC; I think you would probably be better off using a software serial to talk to the GPRS module, if you can get that to work. Or get an Arduino with two hardware serial ports.)
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Great project!  I can do it using Xbee or Wifi+Mifi.  Do you have a serial camera?
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I'm not familiar with that module, but it looks as if it has a uart and I assume that's the one that is expecting to receive your data. Does it have a uart? Is the Arduino connected to it and using the correct serial settings? Is the Arduino receiving "CONNECT" at the right time? The code seems to be sending the data over the Arduino's hardware serial port, so unless you have connected the Rx/Tx lines to the GPRS module's Tx/Rx lines, I wouldn't expect that to work. (This would mean you can't also use the hardware serial to talk to the PC; I think you would probably be better off using a software serial to talk to the GPRS module, if you can get that to work. Or get an Arduino with two hardware serial ports.)

The GSM module does have a UART. What do you mean by "Is the Arduino connected to it and using the correct serial settings?" I'm running it with the same baud rate.

I'm so sad. :'(
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I found a solution to my problem. I ended up just using a Mega to download the picture from my SD card to my SIM900 module. The mega provides more memory and multiple Serial ports. My project works! If anybody has questions on how to do a project like this, feel free to email me at ted_pham08@yahoo.com. I had so much trouble with this project, I will never let another student go unhelped with this!!!!

PEACE!
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Hello sir. Please me. Im having the same problem. I dont know what to do with the CMMSDOWN. please help me.
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