Problem in module Sim908 - doesnt work

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


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

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

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
 

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.
Click to expand...

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



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?
Click to expand...

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

Kosh
 


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
 
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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 .
 
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
 

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

else check your board and...
 

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
 
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That's Great..
 

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...
 

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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...
Click to expand...

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

Regards
 

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

Regards
Click to expand...
 

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
Click to expand...
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...
Click to expand...
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 .... :|
 
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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 ^^
 
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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
 

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

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

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