Datasheet of Sim808L says: in case of trouble, reset module by pulling low the RST-pin for 100ms. When breakout is powerd, the RST-pin reads 1,36V. I know how to pull down a pin on the UNO, but I have no idea how to pull low a pin on this Sim808L for 100ms. Can anybody explain?
The obvious way is connect an Arduino pin to the RST pin on the Sim808L and to take the Arduino pin LOW when required, assuming that the two systems have a common GND connection
In common logic parlance, positive is "high" or "up" and negative which is usually the ground reference is "low" or "down".
Tx UKheliBob. I understand. Yet I wonder. The RST pin should be pulled low for 100ms, but when I set Arduino pin high after that time will the 5V not destroy my module?
when I set Arduino pin high after that time will the 5V not destroy my module?
If the module runs on 5V (does it ?) then its inputs should be 5V tolerant
If the module uses say 3V3 then you are right to be cautious
How is the module powered ?
Module SIM808L is powered with LIPO 3.7V 2000mA. Module is not 5V tolerant. It So I just read about voltage divider at sparkfun tutorial, I think I have to study that. Datasheet only says: pull pin low for 105 ms, no mention of what to do thereafter. Pull pin high? Or maybe leave RST-pin floating?
No just use an open collector transistor.
Arduino output to one end of a 1K resistor, the other end of the resistor to the base of a NPN transistor. Emitter of this transistor to ground. Make the ground common to the Arduino and your module. Finally connect the collector of the transistor to the reset input of your module.
Then write HIGH to that Arduino output pin to reset your module. Write LOW to make your module run.
So I just read about voltage divider at sparkfun tutorial,
So forget them, it is not useful for what you are trying to do.
Well Mike, thank you for your solution! I'll try it tomorrow, and will let you know!
This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.