Problem in module Sim908 - doesnt work

behnam9856 · Aug 19, 2012

It works with 7805 but I offer LM2576-adj regulator which supports 3A output.

it's very good for GSM/GPS modules...

vipintruder · Aug 22, 2012

Kosh said:
You can and you must write, according to the datasheet. Read it.

I read it, when I talk about (RS232-TTL conversor) I am talking about the circuit with the MAX232... etc, etc.

If you can not offer a constructive answer, I think the best option is not say any.

I construct the circuit acording to your schematic (https://www.novinupload.com/uploads/13452712681.png). I am having the same problem. When I turn on Sim908, It just send IIII, and I do not receive any response to AT commands and I can not set the baudrate ofcourse.

Do any have any idea to solve this problem?

Best regards,

vipintruder

Kosh · Aug 23, 2012

vipintruder said:
I read it, when I talk about (RS232-TTL conversor) I am talking about the circuit with the MAX232... etc, etc.

If you can not offer a constructive answer, I think the best option is not say any.

Read the datasheet is a very constructive answer in your case.

I construct the circuit acording to your schematic (https://www.novinupload.com/uploads/13452712681.png). I am having the same problem. When I turn on Sim908, It just send IIII, and I do not receive any response to AT commands and I can not set the baudrate ofcourse.

My schematic? I didn't post that thing and never would do. If you build that, it is obvious you need to read and understand the datasheet.

Do any have any idea to solve this problem?

Yes, read the datasheet and build the circuits according to it.
Not respecting the voltage levels is a road to many problems.

Kosh

behnam9856 · Aug 23, 2012

vipintruder said:
I construct the circuit acording to your schematic (https://www.novinupload.com/uploads/13452712681.png). I am having the same problem. When I turn on Sim908, It just send IIII, and I do not receive any response to AT commands and I can not set the baudrate ofcourse.

Do any have any idea to solve this problem?

Best regards,

vipintruder

if it's for the first time that you're using sim908, also u just see IIII and nothing more, try to send "AT" to the module 7-8 times!

so sim908 detects selected baud rate automatically and then you'll see OK...

then send at+ipr=9600 command to set module baud rate to 9600

sherazi · Aug 23, 2012

when sending "AT" do remeber to send in uppercase. For sim900 or 908 or other device, you should send AT in caps so that the module identifies the baudrate .

Troelli · Aug 23, 2012

Hi
Got the same problems here. IIII
Do you try to syncronise over the debug port or over normal Pins 66 - 72?
Do you use only txd and rxd ? Is dtr connected with ground?
My connection is established to my Provider. I can see it on the Leds.
But i can't get access over rs232.
Which kind of flowcontrol do you use ? (on debug port)
And strange is that i send an AT and he send me a AT back. Not a OK ???
Any hints?
Greets Troelli

Sorry for my bad english ^^

sherazi · Aug 23, 2012

Troelli said:
Hi
Got the same problems here. IIII
Do you try to syncronise over the debug port or over normal Pins 66 - 72?
Do you use only txd and rxd ? Is dtr connected with ground?
My connection is established to my Provider. I can see it on the Leds.
But i can't get access over rs232.
Which kind of flowcontrol do you use ? (on debug port)
And strange is that i send an AT and he send me a AT back. Not a OK ???
Any hints?
Greets Troelli

Sorry for my bad english ^^

I use the main Tx Rx, Tx connects to Rx of max323 and Rx to Tx of max.

if you send AT and you get AT in response ... try sending "abcd" if you get "abcd" in response then that means that your connection/circuit has a fault ...
Try this and let me know

Best of Luck

behnam9856 · Aug 23, 2012

When u get what you sent,it means the echo is on! turn it off...

else check your board and...

vipintruder · Aug 23, 2012

I solved my problem, the MAX232 was not ok. I changed the MAX232 and now SIM908 worked correctly (without read the datasheet... xD).

Seriously, I read the datasheet. The MAX232 circuit in (Kosh's... ;P) schematic work fine.

Thanks for all.

vipintruder

sherazi · Aug 23, 2012

vipintruder said:
I solved my problem, the MAX232 was not ok. I changed the MAX232 and now SIM908 worked correctly (without read the datasheet... xD).

Seriously, I read the datasheet. The MAX232 circuit in (Kosh's... ;P) schematic work fine.

Thanks for all.

vipintruder

That's Great..

behnam9856 · Aug 23, 2012

great...

If your are using Max232 and +5V, I strongly recommend to use Max3232 or level shifter circuit, otherwise the RX pin of your module will be damage after several use...

vipintruder · Aug 24, 2012

- - - Updated - - -

behnam9856 said:
great...

If your are using Max232 and +5V, I strongly recommend to use Max3232 or level shifter circuit, otherwise the RX pin of your module will be damage after several use...

Ok, thank you for this information. I will design my final circuit with it.

Regards

kvtal · Aug 24, 2012

hi vipintruder can u post ur scematic and code
what is ur application im doing an app that saves gps locations to a web server for certain time intervels..

vipintruder said:
- - - Updated - - -

Ok, thank you for this information. I will design my final circuit with it.

Regards

Troelli · Aug 24, 2012

So ... what I found out:
To get the 49 49 49 49 FF FF FF FF on debug port is normal.
Did you pull down DTR as recommended and described in S.15 (Sim908 Hardware Design V1.06 Pdf)?

if you send AT and you get AT in response ... try sending "abcd" if you get "abcd" in response then that means that your connection/circuit has a fault ...
Try this and let me know

I send "AT" and I get "AT" back . If I send more like "AT+CMTE" i get "AT" back. Thats so strange ...
The Device seems to be ok with all functions accept the rs232 part.

When u get what you sent,it means the echo is on! turn it off...

Seems to be an Echo ... but it isn't. How should I turn it off If i haven't access to the Device via RS232?

I have no Idea how i should solve this problem .... :|

vipintruder · Aug 25, 2012

kvtal:

I'm working adapting an existing project to my needs.

The basic project is this: https://www.open-electronics.org/localizer-with-sim908-module/

In that web, you can find all information about it, the gerbers, the source code, etc.

I hope you find it useful.

Regards,

vipintruder

kvtal · Aug 26, 2012

k thank you very much

Troelli · Aug 27, 2012

Hi

I was able to solve my problem ^^ An interrupt issue ^^
But the next problem:
I try to change the time on the Sim908 but he don't let me do this.
I send AT+CCLK="12/08/27,12:25:54+08" and the answer is +CME ERROR: operation not allowed
Does anybody knows what it mean? :?:

lol .... i found it ^^ Problem solved ^^

computerwolf · Oct 14, 2012

you must try windows xp

Amalinda · Jan 25, 2013

here's my pcb in altium designer 9.4

**broken link removed**

Could you pls upload your schematic again? the link says its anavailable. thank you so much

Nivan · Jun 21, 2013

hie behnam I had the same problem,the modem is not registered to network can you help me in getting it registered.
Thanks

- - - Updated - - -

I am using Arduino uno and dfrobot gsm/gps shield with sim908 on it.

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