[SOLVED] problem with using sim800

[ultrasonic.1991]

hi, I want to test a sim 800 header board by connecting it to a USB to TTL module and giving AT commands. I used the LM2596 module for the supply and connected the pins as shown in the picture. It doesn't give any response to AT commands, not even AT. It is noteworthy to mention that the PWR LED on top left is on but the net and stat LEDs only light up every two minutes for a few seconds. Can anyone tell me what is the problem? Did I connect the pins correctly? thanks in advance.

 

[KlausST]

Hi,

Wrong baud rate?
Wrong voltage levels?

We can not verify...

Klaus

 

[ultrasonic.1991]

I checked the voltage with a multimeter it is 4 volts which is correct according to the datasheet. I set the baud rate to 9600.

 

[ultrasonic.1991]

I fixed the problem. I increased the voltage to 4.3 and used single strand wire instead of jumpers and breadboard. Now it's responding to all at commands although the AT+CBC still shows 3.6 for the supply voltage. that's strange.

 

[KlausST]

Hi,

A photo of your wiring could have shown this....

A breadboard is not useful for:
* high currents
* high frequency
* high precision
* low noise

But besides the breadboard problems you need
* correct wiring scheme
* low length
* thick wires
* sufficient bulk capacitor
...

We even didn't know about a "breadboard".
This is what I've meant with "We can not verify .." ;-)

Maybe next time you just take a photo of the whole circuit.

Klaus