I am designing a atmega 328 based irrigation syatem, my circuit contains a gsm module(sim800). Now no io pins available for driving powerkey of the gsm module(my gsm module has no breakout board). I found some details in the datasheet says "PWRKEY should be pulled low at least 1 second and then released to power on/down the module." how can set module power on when power supply is ON. please give me a solution.sorry,my English is poor