GSM TC35 R2 with arduino (can not send message)

Hi guys

My project is sending sms message include the temperature taken by LM35 sensor.
I tested the sensor and gave me the real temperature using serial monitor (ok).
my problem now is with GSM TC35 R2 connection to Arduino uno, I’v tried many connection but no message is sent to the telephone number.
My GSM module is same as in the link below :

I tried connecting pin(9,10) from group p5 and pin (3,6) from group p4 to pin (2,3) in the uno, I powered the GSM from uno
, pin 3 from group p5 to 5V and pin 4 to ground.
and my code :

#include <SoftwareSerial.h> 
SoftwareSerial gsmSerial(2,3);
float tempC;
int tempPin = A0;

void setup()
void loop() 
tempC = analogRead(tempPin);           
tempC = (5.0 * tempC * 100.0)/1024.0;  
Serial.println("temp is");             
Serial.println("  degree C");  
void sendTextMessage() {
gsmSerial.println("Temp: ");
gsmSerial.println(" C");

Is the problem in the connection, the code or else??
please help

Where to start…

  1. tc35 is a DCE device so connect TX to uno TX AND RX TO uni RX i.e do not cross

  2. Read spec for TC35 5 volts at 2 Amps you can reduce this by removing the RS232 convereter chip you do not need unless you are interfacing with terminal on 9 pin D type.

  3. The uno 5 volts however is no where neearpowerful enough… you need an external 5 volt supply via the external connector.

  4. when you have sorted that hit reset button if the SIM card is OK this will reset and register TC35 + SIM card with local operator

The LED should briefly flash about every 2 seconds when registered. Your code will never work… don;t believe the code you find on internet, the sequence will be right…

but it requires Synchronization not delays…

Firt you need to issue
AT… wait for OK can take a second can take 30 seconds
ATE0 turn off echo again wait for OK
Suggest you also look at manual on Siemens and issue operator confirmation and get signal strength, theres no point trying to send SMS if no signal !

Now set SMS mode to text as you did but wait for OK
If you send before OK another command or data the Modem will go into an error recovery and forget everything you have previously done.

Now the SMS sequence, yes you issue command with phone number
The timing of responce here very variable from a <1 second to possible 10 seconds why…
the modem is negotiating circuits to send your text with the operator…
the response here is a > character. in fact it then the >

You must not send anything until this reply occurs if you do general the TC35 locks up

Never send anything before expected replys … so send msg and cntrl terminator but then wait for OK reply

Its only after the OK that you can assume msg gone.

I have used many TC35 modules both v1 and 2 its a brilliant modem but you have to realize it needs synchronization at all stages in its driven code delays simply do not work…

happy coding …