PIC16F877A with SIM900 TTL interface design input

[dhanraj_kmr]

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?

 

[jayanth.devarayanadurga]

Use a voltage level translator.

 

[dhanraj_kmr]

I am not familiar with hardware much. can you point me what you are referring to. any link or diagram?

 

[jayanth.devarayanadurga]

https://www.ti.com/lit/an/scea040/scea040.pdf

 

[dhanraj_kmr]

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?

 

[embpic]

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

 

[dhanraj_kmr]

I think connecting diode is not useful for TX,RX lines.

 

[embpic]

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.

 

[dhanraj_kmr]

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?

 

[embpic]

@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

 

[dhanraj_kmr]

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.

@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

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.