I2C trouble interfacing the Sensirion SDP810 differential pressure sensor

[JohanThomsen]

Hi guys

I'm trying to make the Sensirion SDP810 differential pressure sensor work with my Teensy 3.2. (datasheet: https://docs.rs-online.com/dd4e/0900766b81568896.pdf), but nothing works so far.

First, I tried to use the Arduino library Sensirion has provided on their GitHub (https://github.com/Sensirion/arduino-sdp) with the following code (taken from the library example):

#include <Wire.h>

#include <sdpsensor.h>

SDP8XXSensor sdp;

void setup() {
  Wire.begin();
  //Wire.setClock(100000);
  Serial.begin(9600);
  delay(1000); // let serial console settle
  do {
    int ret = sdp.init();
    if (ret == 0) {
      Serial.print("init(): success\n");
      break;
    } else {
      Serial.print("init(): failed, ret = ");
      Serial.println(ret);
      delay(1000);
    }
  } while(true);
}

void loop() {
  int ret = sdp.readSample();
  if (ret == 0) {
    Serial.print("Differential pressure: ");
    Serial.print(sdp.getDifferentialPressure());
    Serial.print("Pa | ");

    Serial.print("Temp: ");
    Serial.print(sdp.getTemperature());
    Serial.print("C\n");
  } else {
    Serial.print("Error in readSample(), ret = ");
    Serial.println(ret);
  }

  delay(500);
}

This code works just fine on an Arduino UNO R3, but results in an "init(): failed, ret = 1" in the Serial Monitor on the Teensy 3.2.
I simply don't understand why that is?

I also found on this forum, that other's had the same issue with this exact sensor: https://forum.pjrc.com/threads/47868-I2C-pains-with-Sensirion-Pressure-Sensor-SDP810
Based on this post, I tried the following code, but still no luck:

#include "Wire.h"

void setup() {
  Wire.begin();
  Serial.begin(9600);

}

void loop() {
  uint16_t combined;  //32 bit variable to store the msb and lsb

  byte msb;    
  byte lsb;
  
  Wire.beginTransmission(0x25); 
  Wire.write(0x361E);
  Wire.endTransmission();
   
  Wire.requestFrom(0x25, 2);     // contents of your first two bytes
  delay(8);                               //first measurement is available after 8ms, on page 7
  msb = Wire.read();               //byte1 is msb
  lsb = Wire.read();                //byte2 is lsb
  combined = msb<<8;                //assign msb to combined variable
  combined |= lsb;              //add the lsb to the combined variable
  Serial.println(combined);   //print the differential pressure
  delay(500); 
}

Here, the Serial Monitor just prints "65535" no matter the actual pressure.
I triple-checked the Wiring and tried three different Teensy boards, so I'm pretty sure that the issue lies in the code.

Help is much appreciated!
Best regards
Johan