To power on the sim908

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mohanpatil

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Hi Friends,


Friends i am facing the problem that i want to power on the sim908 which is done by pin3 of sim908 called POWERKEY and it is connected to pin83 of STM32F103VE to port D's pin 0 for that i tried to set the BSRR register of PORTD to 1 for 1 second by using delay. and also there is no such indicator on my board so that i could understand the sim908 is powered on so please help me if u know .......

Regards
Mohan
 

Hi Mohan,

First let me state that I am not familiar with ST MCU's.

With that said there are several issues with driving the POWERKEY from a MCU as follows.

The POWERKEY should be driven by a open collector (drain) output of a external transistor.

You can however drive it from a MCU pin if the pin can be configured for open drain output and if the pin has a pullup that also needs to be disabled.
The initial state of the MCU Pin is then set high and the pulled low > 1 second.

As for monitoring if the SIM908 powered up Pin 52 will go high, also Pin 53 will pulse (see data sheet for info).

Last but not least, study study the SIM908 datasheet.

Azlan.
 

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