GM,
OK I did it by your instructions.
Appears to work but the numbers are different?
HTH
GL 
code + Chop
//----------------------------------------------------------------------------------------------
//CHOP CHOP
//Board Library : Seeed nRF52 mbed-enable Borads 2.9.1
//Board Select : Seeed nRF52 mbed-enable Borads / Seeed XIAO BLE - (nRF52840)
//2023/02/12
//Arduino15\packages\Seeeduino\hardware\mbed\2.9.1\variants\SEEED_XIAO_NRF52840/
// replase pins_arduino.h and variant.cpp
//----------------------------------------------------------------------------------------------
#include <Arduino.h>
#include <U8x8lib.h>
//#define LED LED_BUILTIN // default
//#define LED LEDR
#define LED LEDG
//#define LED LEDB
//#define LED P0_26 // RED
//#define LED P0_30 // GREEN
//#define LED P0_6 // BLUE
//Create a instance of class
U8X8_SSD1306_128X64_NONAME_HW_I2C u8x8(/* clock=*/PIN_WIRE_SCL, /* data=*/PIN_WIRE_SDA, /* reset=*/U8X8_PIN_NONE); // OLEDs without Reset of the Display
const int analogInPin = PIN_VBAT;
bool state = false;
void setup() {
Serial.begin(9600);
while (!Serial);
delay(3000);//relax...Get Ready for serial port
Serial.println();
Serial.println("Power ON \n "); // Let's BEGIN!!
Serial.println("Test program compiled on " __DATE__ " at " __TIME__);
Serial.println();
Serial.println("Processor came out of reset.");
u8x8.begin();
u8x8.setFlipMode(1); // set number from 1 to 3, the screen word will rotary 180
u8x8.setFont(u8x8_font_8x13B_1x2_r);
u8x8.clearDisplay();
u8x8.setCursor(0, 0);
u8x8.print("Power ON ");
delay(3000);
pinMode(PIN_VBAT_ENABLE, OUTPUT); // P0_14
digitalWrite(PIN_VBAT_ENABLE, LOW);
pinMode(PIN_CHARGE_HIGH, OUTPUT); // P0_13
digitalWrite(PIN_CHARGE_HIGH, LOW);
}
void loop() {
state = !state;
digitalWrite(LED, (state ? LOW: HIGH));
digitalWrite(LED, state);
u8x8.clearDisplay();
u8x8.setCursor(0, 0);
u8x8.print("PIN_VBAT=");
u8x8.setCursor(3, 2);
u8x8.print((analogRead(PIN_VBAT) * 3 * 3300) / 1024);
digitalWrite(LED_GREEN, LOW);
u8x8.setCursor(0, 4);
u8x8.print(" P0_31=");
u8x8.setCursor(3, 6);
u8x8.print((analogRead(P0_31) * 3 * 3300) / 1024);
Serial.print("PIN_VBAT=");
Serial.print((analogRead(PIN_VBAT) * 3 * 3300) / 1024);
Serial.print(" P0_31=");
Serial.print((analogRead(P0_31) * 3 * 3300) / 1024);
Serial.println();
delay(500);
setupblink();
}
//========================functions===============
void initdisplay() {
pinMode(LEDR, OUTPUT); // initialize the LED pin as an output:
pinMode(LEDG, OUTPUT); // initialize the LED pin as an output:
pinMode(LEDB, OUTPUT);
pinMode(LED_BUILTIN, OUTPUT); // initialize the LED pin as an output:
u8x8.begin();
u8x8.setFlipMode(1); // set number from 1 to 3, the screen word will rotary 180
u8x8.setFont(u8x8_font_8x13B_1x2_r);
u8x8.clearDisplay();
u8x8.setCursor(0, 0);
u8x8.print("Power ON ");
}
void setupblink() {
setLedRGB(false, true, false); // Red
delay(1000);
setLedRGB(true, false, false); // Green
delay(1000);
setLedRGB(false, false, true); // Blue
delay(1000);
setLedRGB(false, false, false); // OFF
}
void setLedRGB(bool red, bool green, bool blue) {
if (!blue) {
digitalWrite(LEDB, HIGH);
} else {
digitalWrite(LEDB, LOW);
}
if (!green) {
digitalWrite(LEDG, HIGH);
} else {
digitalWrite(LEDG, LOW);
}
if (!red) {
digitalWrite(LEDR, HIGH);
} else {
digitalWrite(LEDR, LOW);
}
}
Output
Power ON
Test program compiled on Feb 14 2023 at 11:59:31
Processor came out of reset.
PIN_VBAT=8343 P0_31=8459
PIN_VBAT=8382 P0_31=8478
PIN_VBAT=8343 P0_31=8527
PIN_VBAT=8353 P0_31=8517
PIN_VBAT=8343 P0_31=8488
PIN_VBAT=8333 P0_31=8459