Hello, I’ve hooked up a sim800 gsm modem on an UNO (pin 0, 1). I wrote a simple sketch which sends 2 modem commands over the serial connection. First setup a call, delay 5 seconds and then disconnect the call. When I upload the sketch from the arduino ide everything works fine (tx is lid, modem rec…

Serial (UART) communication

MarkT October 17, 2017, 11:08am 3

I suspect you have to wait a while after powering up the GSM modem before it can connect. It
has to negotiate with the network.

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