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[SOLVED] Telit GSM Modem Interface Help

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gokkul

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The schematic attached is of Telit GL865-Dual GSM/GPRS Modem.

I have omitted the sim connector in the schematic "sim is connected to the modem".

ISSUE:

On power on the "powmon" pin goes high - i am assuming the module is functional, but no indication on the status led
and the module does not respond to AT commands.

I have connected the circuit to a power supply with current indicator, i tried calling the sim attached to the module and the current went
to 200mA and when call terminated it was down to 40mA approx. -- seems like the module registers the sim to the network, but no
indication on status led.


Help appreciated

Regards
Gokkul
 

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  • telit-sch.pdf
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I need to know if the ULN2003 based level shifter will work fine.

little help people ???/
 

Hi gokkul, after going thru your schematic, i think that ULN2003 based level shifter is inverting the rx-tx line, therefore you are not able to use AT commands. you can omit both ULN2003 and max232, use max3232 instead.
 

@ s_guria

The uln2003 actually was working fine actually but i had crossed the RX-TX line (telit modem has the lines crossed actually).

The controller TX goes to modem TX and controller RX goes to modem RX, usually we cross it with all other devices so i did the same :) my mistake

anyway help appreciated thanks
 

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