On some document I find this :
To check if the device has powered on, the hardware line PWRMON should bemonitored. After 900ms the line raised up the device could be considered powered on.
but when is PWRMON go low if switch module off? is there delay ??
first go PWRMON go low (some delay) and then GSM module is OFF?
how it work?
and if power on gsm module, must be the first command AT or can be different?
There is no point in having such a delay: at power on you need to perform some actions while at power off you simply enter an inactivity period without any action, and is hard to believe this period is less than say at least few seconds – which makes the delay check unnecessary.
You can start with whatever command you fell appropriate, the AT is not mandatory.
why I give this question?
on datasheet is write :
In order to avoid a back powering effect it is recommended to avoid having any HIGHlogic level signal applied to the digital pins of the GE865 when the module is poweredoff or during an ON/OFF transition. but all who use external mcu then have connected Tx pin on MCU to Rx pin on GSM module. My MCU is powered with VBAT (4V) but Tx output pin is connected to small AND gate for logic translate to 2.8V (maximum for Rx input in GSM module), also still is 2.8V connected to Rx pin, if GSM module is Off on Rx pin is 2.8V and I want solve this with this solution . input A of my AND gate connect to Tx MCU and input B of gate connect to PWRMON. if GSM module is OFF then on PWRMON is log 0 and output of my AND gate is still 0 and no matter what logic state is on MCU Tx pin. IF turn On GSM module then after 900ms is PWRMON change to log 1 and I can comunicate with GSM module . but what happens if send send command for switch off module? first go PWRMON to low and then switch off or what .
I only want protect Rx pin on GSM module.
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