M5stack BASIC v2.6 GPIO16 input problem

[kazyam53]

I want to use GPIO16 on M5stack basic v2.6 as digital input but it doesn't work.
I have tried on the code below but it always return 1.
・It's work well on M5 stack gray (default 0, when input 3.3V it return 1).
・In case I use GPIO17,25,26, it can also work well.
・I have 2 of basic v2.6 but both of them have same issue.

This is the code I have tested.

#include "Wire.h"
#include <M5Stack.h>

#define DIN 16
void setup() {
  //start serial connection
  M5.begin();
  M5.Power.begin();
  Wire.begin();
  Serial.begin(9600);
  pinMode(DIN, INPUT_PULLDOWN);
}

void loop() {
  int sensorVal = digitalRead(DIN);
  Serial.println(sensorVal);
}

Do you have any solution or find issue on my code?
Thank you in advance for your help.

[felmue]

Hello @kazyam53

M5Stack basic v2.6 seems to have some kind of pull-up resistor (about 3.3 k) on GPIO16. Not sure why and not sure why only on GPIO16.

That said, you'll need to change your code to pinMode(DIN, INPUT_PULLUP); and then either leave GPIO16 open (reads 1) or connected to GND (read 0).

Thanks
Felix

[kazyam53]

@felmue
Then I need to change design... thank you so much for answer.

[macsbug]

Hello @kazyam53

M5Stack Basic V2.6

There is a small clearance between the M-BUS and the metal surface on the back of the Speaker, and some are in contact with each other.
There is a risk of short circuit of M-BUS (GND, 23,19,18,3,16,21).

[felmue]

Hello @macsbug

I've noticed that too. However there is insulation (capton tape) on the back of the speaker in my M5Stack base v2.6.

Thanks
Felix