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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.
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