Hi
in the datasheet is mentioned about PWRKEY. tie to ground for 1.5s for on/off power
but on SIM800L I didnt find that pin
pls advise how I can by software(programmatically) make power down/up modem?
Some modules break out the PWRKEY...
Others, do not...
I have this one. red board. can I use some pin in red board for as PWRKEY?
alexblade:
I have this one. red board. can I use some pin in red board for as PWRKEY?
According to the datasheet, PWRKEY is on pin 48 of the land grid array. The module you've selected, doesn't break it out and I'm guessing you don't want to try desoldering the LGA to hack it, so no....
SIM800 Series_AT Command Manual_V1.09
page 146
"AT+CPOWD=1" - normal power off
"AT+CPOWD=0" - abnormal power off
andyroid, and how after that wake up it by MCU 
?
Perehama, very sad 
power down "1" (normal) means "disconnect from network, save critical parameters and then STOP working". It is just for evolving the correct procedure to stop.
power down "0" (ubnormal) is "emergency shut down"
Nothing means "power save"
So, you need to control (activate / deactivate) the power supply for example
for power ON :
activate a digital output, control a transistor, control power, -> give power to module
for power off:
use "AT+CPOWD=1" - normal power off as said above by andyroid
wait the time is mentioned in databook
DEactivate the digital output, control the transistor, control power, -> stop giving power to module
If you opt for the usage of an external transistor to switch on/off the power to the module(s), make sure to: 1) get a transistor that can handle the required current and: 2) Use the transistor as common collector in order to switch the GND and not the Vcc.
thank you
For sleep applications use:
AT+CSCLK=2: This will put the modem into sleep where current is about 1.3mA, use an interrupt (FALLING) on the DTR pin to wake, or simply just call or SMS the modem.
look for sim800 AT command manual.
sim800 Hardware design.
It will benefit if you have these