PIC16F877A with SIM900 TTL interface design input

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dhanraj_kmr

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Hi,
I am going to start a project based on PIC16F877A with SIM900A module. Since i am not going to use MAX232 i will be interfacing TX, RX directly to the micro. But i understand that PIC operates at 5 volts whereas SIM900A operates at 3.3 volts.

So how to convert the voltage level here to make it compatible with each other communication.

And i heard that PIC16F877A is going to be EOL. So is there any exact replacement of this IC which can support PIC16F877A firmware file as it is?
 

Thanks for your reply.

And another question is that how to read the phone numbers stored in the sim card using a micro controller? is it through commands or something else?
 

ok your PIC controller opearate at 5V and sim operate at 3.3 - 4.3V ok. then use diode in between 5V and supply of sim900a.means as follow

u can use no of diode to decrease voltage because diode oparate after 0.7v so every time ur 0.7v reduce that is 5-0.7=4.3v

+5Volt----|>|------Sim900a supply
 

why not but u have to consider about direction of diode that is for rx it should be towards reciever and if it is tx then it is towards tx side.

- - - Updated - - -

that is direction will be opposite to each other.
 

Thanks for your reply.

And another question is that how to read the phone numbers stored in the sim card using a micro controller? is it through commands or something else?
 

@dhanraj_kmr actually i am also doing work on same project. you can read it directly through UART by using AT+ commands.

- - - Updated - - -

datenblaetter.physicalcomputing.at/AT_Commands.pdf
www.otto.co.za/store/.../c9ab7c3611a421052a675bf6ee332cab.pdf
www.otto.co.za/store/.../1be0954814643cba0bebabfc07f09a73.pdf
www.otto.co.za/store/.../e7ba1d601d05086326640547b6f82314.pdf
rwsdev.net/wp-content/uploads/.../Sim900-rev01-Application-Note.pdf‎

refer these link will help you.

regards
 
embpic said:
why not but u have to consider about direction of diode that is for rx it should be towards reciever and if it is tx then it is towards tx side.

- - - Updated - - -

that is direction will be opposite to each other.
Click to expand...


Thanks for your help. As you said you are working on the same project does that mean you have interfaced PIC16f877A or similar 5 Volt IC with a SIM900a or similar 3.3v modem using USART?

And its communicating as expected?
Before try on the hardware i am making sure it would work. If possible show the schematic or circuit of that particular part.
 

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