SIM 800C interfacing

This is my first circuit following the Datasheet of SIM800C. I’ve tried to design a simple interfacing between atmega 328 and SIM800C. But I’m bit skeptical about the design as this is my first design. Can some one please go through the schematic and let me know if I’m doing something wrong…

Thank u very much!!


The schematic is looking blur, is it bad network or image itself is lower resolution, can you check and upload a higher resolution?

Ok… Please take a look at this attached image.
Is it clear now ?

You have to use level translator chip and use VDD_EXT for translation. You can use TXS0104 chip for it and connecting DTR pin to MCU through level translator will help in controlling sleep modes.

Thank you Ravi. I realised it lately and following the documentation I’ve come up with the circuit shown below. Please take a look

I havent tried the transistor based level translation. I would recommend TXS0102 or TXS0104 for level translation. They work flawlessly.

What about bss138 ? Have you tested this mosfet for level conversation. ? Sparkfun uses this mosfet in thire converter board. And I have used in my esp32 controller design for i2c path. It work fine.

I use BSS138 for other purposes but havent tried for level translation. I dont like transistor based solutions because they take up more space and need extra components like resistors.

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Dear ravi sir,
I need to send data through port 2092 port through tcp to a Linux server using sim800c. Will sim800c Support tcp/ip connections?

Please make a separate thread for your topic.