Wiring:
I connected a 4v (up tp 1.2A) power source to the module Vcc pin (using dc to dc converter).
The TX pin from the sim module go (directly) to the RX serial2 (hardware serial2 on the mega board) pin on the Arduino and the RX sim pin go to the TX Arduino pin.
I uploaded a sketch that will direct Serial data to Serial2 and vice versa.
The problem is that i am sending "AT" command (simply by typing 'AT' in the Arduino IDE terminal with both NL & CR option checked, and press enter) and i am getting no respond from the module....
I also tried to use the software serial but with no luck...
the module have a green led that flashing rapidly
anyone have experience with that module?
any help will be grateful
Download my SIM800 prototype application in the file GSM_TEST.INO within the PUBLIC directory/folder on the SD Card web page on the website http://2wg.co.nz/
If you can get that code running you will find that you can enter SIM800 AT commands directly into the Arduino serial monitor (e.g. AT+CSQ) and the application will print the SIM800 GSM module response to the Arduino serial monitor.
The logic and coding to talk to your Arduino application using the serial monitor and for your application to talk to the SIM800 module through mega serial1, 2 or 3 UARTS should be easy to follow.
You can send the same commands via text message to the phone number assigned to the SIM800 GSM module (assuming the module is on the network) and you will get the response from your text message command back by text message.
Make sure your SIM800 module is on the GSM network - it cannot be powered by an Arduino board - you need a 2 AMP power supply. 1.2 amps is likely not enough, the SIM800 modules seem to need 2 amps briefly when connecting to a GSM network - without a full 2 amps they never connect.
You may also need to install an interface converter between your Arduino's 5.0V serial interface and the SIM800's 2.8V serial interface. You can power the SIM800 side of your interface converter with the 2.8V that comes off the SIM800 RST pin.
These units work just fine and come from a proven manufacturer of SIM modules. You just have to hook them up correctly. Be very careful not to connect 5V to the SIM800 VCC pin - over voltage can fry them.
Catweazle, Thanks for your helpful answer, I will check it again with your code, sending a text msg is a good idia because I think maybe the problem is related to the serial comm...
About the ttl level issue... As I write before, I connected the tx pin from arduino directly to the rx pin of the sim module because I saw that this module can handle 5v ttl level (it was written both on the seler page and on the hardware design PDF).
Also the RST pin wasn't connected.
About the power supply, don't you think 1.2A is more than enough just for Getting OK response?
Last one :-), the module should response to "AT" command when so sim is inserted?
Just because someone says they connected a SIM800 to an Arduino at 5 volts for serial communications does not mean you should or that it will work reliably. The SIM800 specification says its serial interface is 2.8 volts as far as I know.
The SIM800 Tx pin goes to a mega serial Rx pin - the SIM800 Rx pin goes to the matching mega serial Tx pin. Nothing to do with the serial monitors pins 2 and 3. I use serial1 on my freetronics ethermega on pins 18 and 19.
No, without a full 2 amps you will likely never connect. Read up of the meaning of the flashing LED on the SIM800 - you should be able to recognise the sequence that means the unit is powered up but not connected.
1.2v is likely enough just to test AT commands from your Arduino.
Yes, you can use AT commands as soon as the SIM800 is powered up. The SIM800 will respond with error messages if you try to send a txt messages when no GSM network connection exists.
I just checked the SIM800 hardware reference. If you are connecting to a non 2.8v serial interface you need special wiring including resistors to adjust the voltage. Direct connection should not be successful and may be damaging.
Hi guys, same problem here.
I have this module: ebay
I connect the module to a cell phone battery and try to communicate to it with an arduino.
I tried several test arduino programs with no luck. Some programs say to connect it to arduinos RX/TX, other to digital pins.. i can never get communication
BUT...
I know the module is ON because I can call the number.
When I call the number, I can see some garbage chars on the serial window, so.. it kind of communicates with the arduino(?). but when I send any commands, I get no response, or action from the sim800. (I try the hang up command to see if it cancels the call, and that does not work).
sending commands by sms does nothing too :S
any thoughts?
macsoft:
Hi guys, same problem here.
I have this module: ebay
I connect the module to a cell phone battery and try to communicate to it with an arduino.
I tried several test arduino programs with no luck. Some programs say to connect it to arduinos RX/TX, other to digital pins.. i can never get communication
BUT...
I know the module is ON because I can call the number.
When I call the number, I can see some garbage chars on the serial window, so.. it kind of communicates with the arduino(?). but when I send any commands, I get no response, or action from the sim800. (I try the hang up command to see if it cancels the call, and that does not work).
sending commands by sms does nothing too :S
any thoughts?
Has anyone got these modules going, I have the same module, it is hooked up to my lab power supply @ 4volts, I have a voltage level converter in between the module and an Arduino, I have uploaded a demo sketch to the arduino but I just can't communicate with it, if anyone can help I would be most grateful...
Yes, all connected, ground to ground, Ard Tx to 800l Rx via LS, Ard Rx to 800l TX via LS, have a flashing green led on 800l, connects at 9600 baud but send AT command and nothing back...tried 2 different 800l modules..
void loop() // run over and over
{
if (mySerial.available())
Serial.write(mySerial.read());
if (Serial.available())
{
while(Serial.available())
{
mySerial.write(Serial.read());
}
mySerial.println();
}
}
It functions only TX from Arduino Leonardo to GSM Module, so, in monitor serie i type "ATDmiCelNumber;" and mi phone rings, i answer, so i type in monitor serie "ATH" and hang up the call, but in monitor serie not show nothing, i type AT (enter) and not show, i from mi mobile phone i send a message to simcard gsm module not shows ... what could be happing?, Thanks.
making a summing up on the solution here after solved same problem working through 3 night.
check the following may get your chip going and save your time.
voltage:
the chip only works exactly between 3.4V ~ 4.4V, < 3.4V you will get a "UNDER-VOLTAGE POWER DOWN" from serial and > 4.4V you will get a "OVER-VOLTAGE POWER DOWN" error message, and you may not have the chance to see this because under unsuitable voltage the chip is just a bad ass.
a quick work around on power supply is to find a cellphone battery, which will most likely give you a stable 3.7V power(at least in China).
if you see a green led keep blinking once per sec nonstop, good for you, that means your chip is good to go.
if you see the green led went out after blinking for 4 or 5 times, that may mean the chip is up but voltage supply is wrong(mostly too high), the chip will be shutdown after the blinking, you may see the error message after a big while if your baud rate is right.
if you see nothing, that means your input voltage is too low, can't drive the chip.
currency
make sure the chip can get > 1amps. i used a 5V1.5A power source, and measured out an currency around 100mA when get an "OK" response on "AT" command.
baud rate
my chip works on 115200 baud rate defaut, try that rate if you see nothing on the right voltage.
pin connection
make sure pins are well welded on the board. this simple sentence costed me a night.
Soft Serial
if you still cant get it going, try to use a hardware serial instead of soft one.
I bougnt This GSM module few days before https://daneshjookit.com/gsm-gprs/2225-sim800-gsm-gprs.html
But I couldn't find any data sheet or valuable document about this module.
Also I couldn't find TX and RX pins (to connect arduino) which are not mention in board.
Could you please help me to find it.... and Sorry for my bad English.
