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I am trying to use a SIM800C GSM/GPRS module for my project. On the datasheet it says:

The power supply range of SIM800C is from 3.4 V to 4.4 V. Recommended voltage is 4.0 V. The transmitting burst will cause voltage drop and the power supply must be able to provide sufficient current up to 2 A.

To use the module I use a voltage supply with 4.2 V and 2.0 A. When I connect the +/- pins of the power supply to the Vcc and GND inputs of the SIM800C, nothing happens. The state LED does not light up, simply nothing happens.

What might be the reason for that? Can this be because of the absence of a capacitor, which is mentioned in the documentation as well?

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    \$\begingroup\$ to the Vcc and GND inputs there's no VCC, there's VBAT. Probably you meant VBAT. Anyway, check the voltage of the VEXT pin. This pin should output 2.8 VDC during normal operation. If there's no or abnormal voltage at this pin then you have either a bad module or a bad power supply. Also, make sure you didn't leave the VRTC pin unconnected. \$\endgroup\$
    – Rohat Kılıç
    Commented Sep 2, 2021 at 10:19
  • \$\begingroup\$ What you said actually helped during one of the other problems I had when I got the module working. Thank you so much for that! I forgot to mention that I was using SIM800C GSM/GPRS module. Sorry about that! \$\endgroup\$
    – kucar
    Commented Sep 3, 2021 at 9:08

1 Answer 1

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So, it turns out that I needed to connect the "BOOT" pin of the module to the ground, to power it on. When I did that the device started working - even though I have problems connecting to the network, its status light works now.

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