After examining the schematic of the WiFi LoRa (V3) board it shows that the OLED display is powered by pin36 which clearly isn’t true. A small sketch switching the pin 36 from high to low doesn’t affect the display at all. I have measured the output of this pin and it behaves as expected. Is the OLED display powered from a different pin or has it just got a permanent supply? This would make it really bad for battery applications. I really need an accurate schematic.
WiFi LoRa 32 (V3) Vext not connected to pin gpio36
Thanks for the reply but the schematic doesnt make sense to me.
I am runniing the sketch below setting Vext gpio pin 36 from on to off every 2 seconds
In theory the display should only show a “1” in the display as when “0” it should have no power and should display nothing.
I have measured with a multimeter the output of Vext (gpio36) and it goes from 3 volt to 0 volt every 2 seconds so the sketch seems to be working as expected.
#include “HT_SSD1306Wire.h”
int myval = 0;
SSD1306Wire display(0x3c, 500000, SDA_OLED, SCL_OLED, GEOMETRY_128_64, RST_OLED); // addr , freq , i2c group , resolution , rst
void setup() {
pinMode(Vext, OUTPUT);
Serial.begin(115200);
VextON();
delay(100);
display.init();
}
void VextON(void) {
digitalWrite(Vext, HIGH);
}
void VextOFF(void) {
digitalWrite(Vext, LOW);
}
void Demo() {
myval = digitalRead(Vext);//read value of Vext pin 36
Serial.println(myval);//send value of Vext to com port
display.drawString(0, 0, String(myval));// show value on screen
}
void loop() {
VextOFF();
display.clear();
Demo();
display.display();
delay(2000);
VextON();
display.clear();
Demo();
display.display();
delay(2000);
}
Vext is shown as being gpio36 but doesnt seem to control the display.
As a point of clarification here, GPIO36 is the Vext-Ctrl pin, not Vext as such. Vext is switched ON and OFF through a MOSFET, which is controlled by GPIO36. Regardless, and in spite of what appears in the Schematic, I agree that the OLED display does not appear to be powered through Vext.
For what it might be worth, I turn the OLED display off explicitly via:
display.displayOff();
then back on again if/when required via:
display.displayOn();
noting that the OLED display needs to be (re)initialised any time it is turned ON, just as it would otherwise be in the setup() function.
Thanks UniquePete for the clarification on the Vext-Ctrl pin. I was a little concerned that display.displayOff wouldn’t fully power down the display but difficult to know what is happening as it doesnt seem to be documented. I have requested clarification from Heltec so will post here if I get more detail.