All right, to answer my own post :
This post helped a lot :
https://community.m5stack.com/topic/1086/problem-when-connecting-more-than-3-ds18b20-temperature-sensors-solved/6

And XX is 21.

I've connected a DS1820 waterproof sensor to the Grove / Port A of the M5basic

GND=black
VCC=red
SDA=yellow

My code is :

#include <M5Stack.h>
#include <OneWire.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS XX
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

void setup(){

M5.begin();
M5.Power.begin();

M5.Lcd.print("onewire temp test");
}

void loop() {
sensors.requestTemperatures();
String text = String(sensors.getTempCByIndex(0),2)+"C";
M5.Lcd.println(text);
delay(800);
M5.Lcd.println("test");
}

for XX, I've tried port 21,22,32,33 and a few other I read rumours about. No success to read the temperature so far. Any clue?

Hi,

has anyone been able to connect a 1 wire ds18b20 waterproof temperature sensor to the m5stack grove connector A?
I see a + and a - port, and an SDA and an SCL port. Can either of those be used to one wire connections? And how would I do that in code?

Thank you so much!

Christian