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Thread: Teensy 3.5 I2C stops working after a while

  1. #1

    Teensy 3.5 I2C stops working after a while

    I made a simple sketch for using the I2C IO Expander MCP23017 with a teensy 3.5 board.
    Using Teensyduino v1.40 with Arduino IDE 1.8.5
    The pullup resistors (4.7k) are OK.
    After a short while (between 5s up to 2min) the expander stops working.

    #include <Wire.h>
    #include "Adafruit_MCP23017.h"
    Adafruit_MCP23017 mcp;
    void setup() {  
      mcp.begin();      // use default address 0
      mcp.pinMode(6, OUTPUT);
      mcp.pinMode(7, OUTPUT);
    void loop() {
      mcp.digitalWrite(6, HIGH);
      mcp.digitalWrite(7, LOW);
      mcp.digitalWrite(6, LOW);
      mcp.digitalWrite(7, HIGH); 
    What's wrong?

  2. #2
    It seems that it is a problem with the chip. I have the same problem on Arduino UNO.

  3. #3
    Senior Member+ Theremingenieur's Avatar
    Join Date
    Feb 2014
    Colmar, France
    Isn't there an improved and optimized wire library, especially for the Teensy 3.x processors?

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