Arduino Mega SIM300S (SOLVED)

Projects Networking, Protocols, and Devices
1

Hi,

I have a Simcom Sim300s
when i connect it using a serial cable to my pc i can call send messages etc.
but if i connect it to my arduino it won't do anything

I tried every library i could find but without result.
i want to use one of the four serial ports. but it won't work
i connected the 2 ports of the serial connector to pin 18 and 19 and connected the gnd's together.
for the connection with my pc and hyperterminal i also used only 3 wires so that should be correct.

so please tell me what do i do wrong do i connect the pins incorrect or am i using the wrong code.

serial1.begin(9600);
Serial1.print("ATD0612345678;");
Serial1.print("\r");

600×1000 84.4 KB

kind regards

Johan

2

I have a Simcom Sim300s
when i connect it using a serial cable to my pc i can call send messages etc.

If you are using a serial cable, not a USB cable, the device is a RS232 device, not a TTL device.

The voltage output, and required voltage input, will not be compatible with the Arduino. You'll need a MAX232 chip in between.

Posting a link to the device, rather than a picture of the the device and a bunch of other stuff, would be more useful.

3

Part of the problem is that the SIM300S IC uses 2.85V IO lines and your Mega uses 5V IO lines. You're sending 5 volt signals to a device that can't handle anything over 3.23 volts (VDD_EXT + 0.3 ) so you should start by either dropping the Mega Tx line over a resistor divider to the correct range and hope the 2.85 V signal is read by the Mega or use some kind of logic level converter to convert both Rx and Tx to the correct levels. If you use a level converter you can use the VDD_EXT pin on the SIM300S as your low side IO supply.

Also you don't need to use the "\r" after each command, just use Serial.println with the AT command and it will work fine.

4

i made a converter for with a max232 and now everything is working fine.

thx for the help.

Kind regards

Johan