Problem with P89V51RD2 interfacing with GSM module (SIM900)

Thread Starter

g_shyam1682

Joined Jan 25, 2010
5
Hello friend,

I have one problem with my GSM base project.
In my project, i use P89v51Rd2 means 5V microcontroller and my GSM module (SIM900) is working at 4.2V, so how can i connect my Micro RX, TX which is at 5V to SIM900 RX, TX which is 4.2V support.

Please help me to design my circuit.
Thanks in advance.

Regards,
Ghanshyam
 

binu_ji

Joined Jul 13, 2007
22
SIm900 tx/rx can work with 5v microcontrollers. You can directly connect microcontroller tx/rx to sim rx/tx.

For sim900 power supply just place a 1n4007 diode which drops 0.7V from 5v.
 
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