analogRead on M5Atom

[sbollaerts]

Hello, I'm trying to make analog readings on pin "G33" and "G23".

• When I do analogRead(33), I get the same values whatever I send the signal on G33 or G23
• When I do analogRead(23), I receive no signal on G33 and G23

What am I missing?

#if !defined(ARDUINO_M5Stick_C)
#error Wrong target platform (M5StickC - M5Atom)
#endif

#include "M5Atom.h"
#include "pixelTypes.h"

uint8_t pinNorth = 33;
//uint8_t pinSouth = 19;

void setup()
{
M5.begin(false, false, true);
Serial.begin(115200);
}

void loop()
{
int readValue;
int ledValue;

// Read the North pin
readValue = analogRead(pinNorth);
ledValue = map(readValue, 0, 4095, 0, 255);
Serial.print("- North: ");
Serial.print(readValue);
Serial.print(" -> ");
Serial.println(ledValue);

M5.dis.drawpix(2, ledValue);
M5.dis.drawpix(6, ledValue);
M5.dis.drawpix(7, ledValue);
M5.dis.drawpix(8, ledValue);

delay(10);

// Read the South pin
// readValue = analogRead(pinSouth);
// ledValue = map(readValue, 0, 4095, 0, 255);
//
// Serial.print("- South: ");
// Serial.print(readValue);
// Serial.print(" -> ");
// Serial.println(ledValue);
//
// M5.dis.drawpix(16, ledValue);
// M5.dis.drawpix(17, ledValue);
// M5.dis.drawpix(18, ledValue);
// M5.dis.drawpix(22, ledValue);
//
// Serial.println("");
// delay(10);
}

[AndyT]

@sbollaerts

Are you usiing a gpio that does not have a ADC?

Ah yes GPIO19 is not an ADC pin.
here is a picture of the pins of the M5Stack
https://www.instructables.com/Automation-With-SIM800L-ESP32-M5Stack/
PINS 35 or 36 are the ADC's

/

[felmue]

Hello @sbollaerts

there is only one analog input available on the M5Atom Matrix: GPIO34 which is shared with GPIO23.

Please check out M5AtomMatrix Schematic

In order to use the analog input you'll need to set GPIO34 as input and disable pullup/pulldown resistors of GPIO23.

Below code works for me:

#include <M5Atom.h>

void setup()
{
  M5.begin(true, false, true);

  pinMode(GPIO_NUM_34, INPUT);
  gpio_pulldown_dis(GPIO_NUM_23);
  gpio_pullup_dis(GPIO_NUM_23);
}

void loop()
{
  Serial.printf("GPIO34: %d\n", analogRead(GPIO_NUM_34));
  delay(1000);
}

Update: I just realised that GPIO33 can also be used as analog input.

  pinMode(GPIO_NUM_33, INPUT);
  Serial.printf("GPIO33: %d\n", analogRead(GPIO_NUM_33));

Cheers
Felix