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Problem in module Sim908 - doesnt work

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behnam9856

behnam9856

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Hi,

when I turn on Sim908, It just send IIII???? and I dont receive anything more!

also when I send AT commands, nothing happens!

and Netlight LED shows that module is not registered in the network, 64ms on, 800ms off

any one can help me plz...

best regards
 

my problems in lat post solved.

sim908 worked correctly and registered into network. but after a few minutes sim908 could not resister to network and i got this error: +CPIN: NOT READY

and after a while i got this for one of our operators +CPIN: NOT INSERTED

with another operator, first of all module send message to enter pin code and after it, some times i get +CPIN: NOT READY and error for AT+CPIN="XXXX"

and sometimes it registers to the network and maybe i shows +CPIN: NOT READY after a while!

anyone know why? plz reply... its urgent to solve this problem,

best regards
 

can u share ur schematic . specially for the Power supply and simcard interface?

if the powersupply cant provide the required power when the GSM module is transmitting , you can have such problems.

Are u using 220nF cap at sim interface?
 

here's shematic.
13361638791.png


it worket correctly before!

i checked voltage on sim vdd and i got that when the module is off, sim vdd is 0.87v and when module turns on, for one second it goes to 1.xx volts and then returns to 0.87 volts.

but with another operator, some times the voltage is 3.x volt on sim vdd and after entering pin code, voltage is 2.x volts... but more times my voltage is on 0.87v

ps: in the schematic as you see, sim card holder is 8 pins (2 pins are hide), but i used 6 pins in pcb
 

A 78M05?????? Didn't you read the SIM908 datasheet?
 

yes, but i used 7805cv in pcb and it works!

I have a sim900 and the regulator's 7805cv... works pretty good!
 
Last edited:

Can you please tell me the solution as I am also facing problem with SIM908.Its not generating SIMVDD. WHen module powers ON,it generates SIM VDD for few milliseconds and then goes to zero.

I am using LM350 for SIM module supply.

Its urgent.Please reply.

Thanks,
AMit


behnam9856 said:
All right... Solved! :-D
Click to expand...
 

allright, my problem was because of GND wire and noise on the circuit!

i designed another PCB with wide GND wire, alsi i used polygon under sim908 and around it...

i used LM75CV and a 1n4007 for power...

here's my pcb in altium designer 9.4

**broken link removed**

hope to help u...

P.S, try to use MAX3232 instead of MAX232 if u're using COM port.
 
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    Rod_O

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Thanks a lot for your reply.
I will try these changes.

regards,
Amit

behnam9856 said:
allright, my problem was because of GND wire and noise on the circuit!

i designed another PCB with wide GND wire, alsi i used polygon under sim908 and around it...

i used LM75CV and a 1n4007 for power...

here's my pcb in altium designer 9.4

**broken link removed**

hope to help u...

P.S, try to use MAX3232 instead of MAX232 if u're using COM port.
Click to expand...
 

Hi, I am vipintruder ;P

behnam9856: Could you tell me how you solve the problem with IIII menssage please?

When I turn on Sim908, It just send IIII... and I dont receive anything more.

Best regards.
 

can u plese repost ur schematic im also trying a circuit with sim908
 


How can I set a baud rate for module like 9600?, because I can't send any AT command.

I have connected the module to my PC by RS-232 (with RS232-TTL conversor). I recived the IIII message only when I configure the software (GtkTerm - "like hyperterminal in Windows") with 115200 bauds, but I can't write any command in it.

Thank you for your response and your help.

Best regards.
 
You can and you must write, according to the datasheet. Read it.
 

than q very much for ur schematic
which microcontroller u used for ur aplication
 

kvtal said:
than q very much for ur schematic
which microcontroller u used for ur aplication
Click to expand...

than q? what u mean?

I used Avr family, ATmega128.

p.s, use MAX3232 instead of max232...
 

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