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By Andrey Fedorov
#80424 Hello,

Two modules SIM800С, ordered from the two different sellers. When I send the AT command AT+CPIN? via USB-to-TTL converter gets respond: +CME ERROR: SIM not inserted
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The error occures when I send any command depending on SIM card.
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PIN code removed from the SIM card. It works in the tablet without any problem.

I connected V_TTL to +5V. As far as I understand on this pin should be voltage corresponding microcontroller
TTL level (+5V or 3,3 V).

V_TTL SIM800C to +5 V
TXD SIM800C to RXD USB-to-TTL
RXD SIM800C to TXD USB-to-TTL
GND SIM800C to GND USB-toTTL
PWX SIM800C shorted to GND.

The module power supplied from the source 5V, 2,1А. Do you have any ideas what I can make?