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SIMCOM SIM300 RXD and TXD pins (how to connect to COM port?)

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hedehede81

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Hello everyone,

I have a SIM300 module and I can only access the top of it, bottom is inaccessible. It doesn't have a ready-made serial interface. I would like to access TXD and RXD pins of SIM300 to connect to my COM port. Since I can only access only top, I was wondering any of those round pins is TXD and RXD. I have found an image:
sim300dz_rs232_low.jpg

As you can see there is yellow TXD and red RXD round pins. My layout from top is a little different:

SIM300.jpg

Could you please tell me what number is TXD and what number is RXD? Can I solder wires to these round pins and connect to my PC COM port with MAX232 interface?

Thank you very much in advance, I hope I can get this working with your help.
 

bogvt

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According to my measurements and taking into consideration your sim300 pin diagram (2nd image)you have:
- pin 1 Rx TTL (Sim300 is receiving your Tx from whatever module you are using)
- pin 7 Tx TTL (Sim 300 is sending messages to Rx pin from your module).

Good luck!
 

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