NodeMCU / ESP8266 - Light Sleep Wakeup via SIM808 RI (Falling Interrupt)
Invert the RI signal of the SIM808 so you will have a rising edge at the ESP8266's pin when RI goes low. You can use a couple of resistors and a NMOSFET.







simulate this circuit &ndash; Schematic created using CircuitLab

When RI is high the WAKEUP pin will be on ground, if RI goes high then WAKEUP will be pulled up to VCC through R2. Here is a simulation, you can click on the left "L/H" to switch the input level.