SIM900 with restart problem

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nenoksl

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Hello, I'm having trouble with restart SIM900 module and would like to know if anyone can help:

First I turn on the power (4.5V), than I powerkey down for 2 seconds and SIM900 is power up normally. Than I powerkey down for 2 seconds again and the SIM900 is turned off, but from this point if I powerkey down for 2 seconds nothing happens, I can't restart the SIM900, does anyone know what might be happening?
 


Why you need to restart SIM900 Module? normally their is no such problem for restarting. After powering off you may switch off than on the the power supply 4.5V
 

I need predict the restart of SIM900 in case of crash. I know if I remove the 4.5V SIM900 operates normally but I would not want to be removing the 4.5V and the SIM900 datasheet does not report the need to remove the power to perform the restart.
 

their is RESET pin for restarting the Module, but it is for EMERGENCY Cases only, SIMcom don't recommend this for several use.
 

I know, so I want to use powerkey to make the restart (but it does not work).
 

PowerKey is just for powering ON and OFF for one time, after that you need to restart your powersupply
 

but see this picture removed from the datasheet:
 

My microcontroller work with 5V and serial SIM900 to 2.85 V, so I have a circuit to the adequacy of the serial signals, and this circuit there were pull-up resistors of 10KOhms. Somehow after I turn off the module these resistors were powerkey influencing the circuit module.

I changed the pull-up resistors to 100KOhms and restart happened normally.

Tanks Masterleous...
 


i have the same problem and i dont know how to fix it? please could you tell me how to doing?
 

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