SIM900D Interfacing with hyper terminal.........

[sherazi]

i am planning to make a pcb for sim900, so i would like to share the schematic here for checking for any error especially with the module section .... thanks in advance

there is some problem with attaching the image plz have a look here urlhttp://teeblog.blog.com/files/2011/07/gsm-schematic.png

 

[kirangowle]

Make sure there is no shorts present while getting soldered the modem.

 

[sherazi]

ya ,,i would, but what about the schematic ,circuit.. is it fine????

 

[uzair_afzal]

How you have solved the problem as i have the same issue with sim900d.It is ot responding to AT commands at all after power up.

 

[Graham1904]

How you have solved the problem as i have the same issue with sim900d.It is ot responding to AT commands at all after power up.

First make sure that the TX line goes to the RX line of the module and vice versa. This is often a mistake by new users. Make SURE that the voltages entering the SIM900 do not exceed the 4V0 of the module. Also I suggest that the 4V0 Vdd supply to the module has suitable caps on the supply line 1 x 2200uF for through hole or 4 x 470uF for SMD.

The default baud rate could also be the problem. Hyper Terminal uses a default of 9,600 but the default of the module is auto-baud or 19,200 and so I suggest that you send an AT+IPR=9600 command and then an AT&W command to make sure that it is saved in its RAM (although SIMCOM state that it is saved automatically).

If you pull-down the PWRKEY line to get the SIM900 to network lock you will not be able to send AT commands until the ARM processor has finished booting up the modem. I suggest you wait for "CALL READY" before sending any more AT's.

Hope it helps.....

 

[raowakeel]

hello sir..i have the same problem..my sim900d is not responding to AT commands..its get hanged when i turn it on..it sends 4 delta on the screen..any help please..

 

[sherazi]

sim900 is set to auto baud by factory default,

what i did was to send at+ipr=xxxx baudrate i am using continously until i got the response Ok,

 

[yousafzai82]

I think the solution is simple...Just enable CAPS LOCK....

 

[raowakeel]

Hi, I am using Simcom SIM900D. I just want to interface this module with PC hyper terminal. I have followed all the precautions and design mention in hardware design. When I power up the module it send "ΔΔΔΔ" on hyper terminal @ 9600 baud rate and send nothing on different baud. (It is mentioned in the manual that it should not send any data when using in auto baud mode). After that it stops responding. Any suggestion to solve this issue??
Thanks in advance
wasif

hi buddy
you gsm is perfect..no listen carefully what i say
when these type of char appear on hyperteminal then switch off you GSM module and by using opower key,..you will see "NORMAL POWER DOWN" on hyperterminal..its mean your circuit working proper..now turn it on again it will start sending soome data on hyperterminal..wait untill call ready appear..now you can write AT commands it will work fine

---------- Post added at 15:25 ---------- Previous post was at 15:22 ----------

one more thing when you interface your sim900d..try to discard 232 IC..connect them directly..they will work fine..because sim900d work on TTL logic..
thanx

---------- Post added at 15:26 ---------- Previous post was at 15:25 ----------

iterFACE MICROCONTROLLER AND gsm SIM900

 

[uzair_afzal]

hello sir..i have the same problem..my sim900d is not responding to AT commands..its get hanged when i turn it on..it sends 4 delta on the screen..any help please..

For SIM900D please always give first AT command in capital letter with caps lock on when you on your GSM. If you type "at" without caps lock it will not respond to any further commands and not even show them on hyper terminal. Good practice is to always on the CAPS lock for AT commands.

 

[ckshivaram]

GSM modems are caseinsensitive. they respond to both capital and small letters. there is no modem that is designed only for small letters or capital letters, and moreover. so i dont think it is quite right, what the above post says is not true. it may be revert to factory settings in any case of problems.

more over the at commands are sent through program, which is irrespective of capital or small.

 

[sherazi]

i have been using LM317 and its OK

 

[cnd]

Hello Everyone

Attention: sherazi, chipseller


It looks like I am also the part of this problem now. I am having the serial interfacing problem with SIM908 module which the combo pack of SIM900(GSM)+SIM08(GPS) modules on genuine SIMCOM SIM908 EVB v1.01 board. I bought the EVB 2 weeks ago form SIMCOM authorized distributor, As I start working on this board from last monday, within few minutes after setting up my EVB I came acroos the problem. Initially I Google for SIM908 module interfacing problem ,but later I figure out this also a interfacing problem with SIM900 and there is long discussion going on on internet. I contacted SIMCOM tech person, but their reply shows lack of interest. On more research I figure out BOTH SIM908 and SIM900 GSM part is same, so I think it cud be common solution to both the modules. Below here I am describing in detail my testing and research procedure what exact we are facing.


Tools using for testing

1. SIMCOM SIM908 EVB_v1.01 Board with SIM908/SIM908-C module on it.


2. Working SIM inserted on board.


3. Power Adapter: I have two Adapters a.5V DC 2A i.e comes with SIM908 EVB and b.12V DC 1A that I also use with the board.

4. RS232 to USB Serial cable for Interfacing GSM MAIN RS232 and Arduino USB Serial Light Adapter for GSM UART TTL Interfacing

5.Realterm Serial capture 2.0.0.57 software and Arduino Serial Monitor Software for testing, debugging.

6.All the docs, datasheet, Schematics, At command listed PDF fo SIM900 and SIM908 on laptop screen .

!!! If i missed any thing here please ask, I will update it.

Interfacing of cables with Board to PC

• I am using both RS232 port and UART TTL for sending command and Monitoring respectively.

• RS232 to USB Serial cable is connected to GSM MAIN (RS232 port) and Arduino USB Serial Light Adapter is connected with GSM UART TTL rx tx pins on board.

• COM 7 and COM 8 represents RS232 to USB Serial as per USB port (my laptop has 4 USB port).

• COM 33 represents Arduino USB Serial Light Adapter on Device manager.

Baud Rate set @ 9600 default.
please check the images for connection reference


Testing procedure , Network Initilization and results

In the images you can see "AT" typed several times . This is done to test the communication of respective cables. Please note this pre-test was taken place while board is powered but SIM908 module is off, I put jumpers on respective TX and RX pins to test this

Now I power on the board and switch on SIM908 module. The below video shows the Network Initialization process. Notice the 2nd middle Blue LED, Initially it blink fast while searching for network and later it blinks much slower rate after entering to network.

But after successful initialization I did not get any status on Realterm screen. But you can notice some garbage value on last line of realterm, this appeared while I switch on the SIM908. Even I hit several "AT" but did not get any of responce from the module. I tried every other baud rates in order to get readable the the garbage value, but did not get any success.

I called to SIM# i.e used with this board from my Mobile, in the result I could hear the ringing on my mobile, but did not get any msg on terminal window.

I also check the same for GPS port also, and again I meet he failure here also. I

I have worked on SIM300 module previously, and completed many projects successfully, but this somthing I am not expecting from the advance modules.
As I saw few of discussion are going on this issue and few of you has got success to get it. I hope will get some support from here

Please note I am facing this problem on genuine SIMCOM EVB. not on 3rd party Board. Thanks a lot for reading and support.

 

[cnd]

sim900 is set to auto baud by factory default,

what i did was to send at+ipr=xxxx baudrate i am using continously until i got the response Ok,

Hey I set my baud rate from device manager and set with sim908 module using above this command, and guess wht i got "ok"... so please remember if you ddnt get to higher baud rate, 1st set host baud rate from device manager and then synchronize with SIM modules. i must work them. Thanks a lots.

 

[raowakeel]

that s not true..my sim900 is working fine with elm317 and 7805..it is sending and receiving messages prfctly..

 

[owdk]

Hi,
Question about voltage on RS232 input on the SIM900d module..

What kind of RS232 interface do you use between the PC and the SIM900d modem module. MAX232 is designed for
5V use and output and SIM900d has a limitation of max. 3.0V on its input.
Did you put in a voltage divider (resistors) between TX from MAX232 and the RX on the module or?

(I know there are MAX232 versions for use with 3v output but for my prototype I don't have this)

 

[Echo wang]

Hi,
Question about voltage on RS232 input on the SIM900d module..

What kind of RS232 interface do you use between the PC and the SIM900d modem module. MAX232 is designed for
5V use and output and SIM900d has a limitation of max. 3.0V on its input.
Did you put in a voltage divider (resistors) between TX from MAX232 and the RX on the module or?

(I know there are MAX232 versions for use with 3v output but for my prototype I don't have this)

Hi, Owdk, pls use SP3238.
Pls kindly fyi the following circuit.


---------- Post added at 14:51 ---------- Previous post was at 14:49 ----------

that s not true..my sim900 is working fine with elm317 and 7805..it is sending and receiving messages prfctly..

Hi, buddy, congratulations!

 

[yousafzai82]

Is there any way to get current time from the network? If there is what are the AT commands for that?

 

[hamidrezamaddah]

Is there any way to get current time from the network? If there is what are the AT commands for that?

you can send a sms to yourself. in received sms you can get date and time

 

[Echo wang]

Is there any way to get current time from the network? If there is what are the AT commands for that?

Hi, yousafzai82, refer to AT+CLTS