[SOLVED] Problem with P89V51RD2 interfacing with GSM module (SIM900)

[g_shyam1682]

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,

 

[amayilsamy]

The built in Low Dropout Linear voltage regulator allows you to connect wide
range of unregulated power supply (4.2V -13V) at supports 1 A.

Connect the GSM Modem to a PC Com port using a MAX-232 circuit or TTL-RS-232/TTLUSB
and Power it Up.

You can use 12 V at 1.5 A both micro controller circuit and GSM Module.

And interfacing the module with the using MAX232 circuit.

You can't directly communicate with the micro controller.

This link having SIM900 Datasheet. Its having MAX 232 Circuit.

https://www.rhydolabz.com/documents/gps_gsm/sim900_rs232_gsm_modem_opn.pdf

I hope its helps you.

 

[g_shyam1682]

Thanks for your reply, amayilsamy

but here i talk about direct communication between SIM900 GSM module (From SIMCom) and micro, not GSM modem. Power supply and all other need circuit i will design myself.
I think, Module Tx to Micro Rx line drive from module side, so need not any addition component and may connect directly.
For, Module Rx to Micro TX line drive from 5V (Micro side), so here i think we should use some type of resister divider circuit.


Regards,

 

[g_shyam1682]

Hello Friend,

Please help me to design Microcontroller ( P89V51RD2 - 5V) direct interfacing with SIM900 (From Simcom, 4.2 V) Circuit myself.

Regards,
Ghanshyam.

 

[amayilsamy]

Post your schematic diagram.

And your modem datasheet.

 

[zia]

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,

it directly communicate.no issue of 4.2 volt

 

[g_shyam1682]

Thanks zia,

Now i am able to communication directly, without any circuit in between.
Now i have one more problem, How to get SCID no. from SIM900a. I google the internet and i find out AT^SCID command to get SCID, but this command is not supported in SIM900a.
Please help me to get SCID no from SIM900a.

Regards,

 

[zia]

may u please mention why u want to use csid, in sim900 for IMEI Number AT+GSN is used and for sim number AT+CNUM? is used (If an Error occurs, number is not set on SIM card)

 

[g_shyam1682]

Thanks Zia

Scid number is used in our Application for Authentication of system.

Regards,

 

[Soumyajit]

Thanks Zia

Scid number is used in our Application for Authentication of system.

Regards,

In our vehicle tracking system, we have successfully used "AT+CCID" for the purpose.