Hello,
I feel like I have to be missing something very simple here. I have connected the Adafruit MCP23017 expander board using the Qwiic connector to my Uno, and using an I2C scanning sketch I can see that it is properly recognized at the default address of 0x20.
I am trying to use a photo interrupt module but cannot get it to work while I have no problems using it directly connected to the Uno's GPIO pins.
As long as the non-transparent object passes through the slot type, it can be triggered to output TTL low level.
Working Sketch while connected directly to the Uno:
#include <Arduino.h>
#define OPTICAL_PIN 2
bool lastOpticalState = HIGH; // Assume the beam starts unblocked
void setup() {
Serial.begin(115200);
pinMode(OPTICAL_PIN, INPUT_PULLUP);
lastOpticalState = digitalRead(OPTICAL_PIN);
}
void loop() {
bool currentOpticalState = digitalRead(OPTICAL_PIN);
if (lastOpticalState != currentOpticalState) {
if (currentOpticalState == LOW) {
Serial.println("Beam BLOCKED");
} else {
Serial.println("Beam UNBLOCKED");
}
lastOpticalState = currentOpticalState;
}
delay(10);
}
This works as expected, when the sensor is blocked, serial prints out "Beam BLOCKED" and when I remove the block, it prints out "Beam UNBLOCKED", so exactly what I am looking for.
When I modified the code to use the Adafruit_MCP23X17 library, connect the module to the expander board (and VCC to the Uno's 5v pin) I get no output:
#include <Arduino.h>
#include <Adafruit_MCP23X17.h>
#define OPTICAL_PIN 0
Adafruit_MCP23X17 mcp;
bool lastOpticalState = HIGH; // Assume the beam starts unblocked
void setup() {
Serial.begin(115200);
mcp.begin_I2C();
mcp.pinMode(OPTICAL_PIN, INPUT_PULLUP);
lastOpticalState = mcp.digitalRead(OPTICAL_PIN);
}
void loop() {
bool currentOpticalState = mcp.digitalRead(OPTICAL_PIN);
if (lastOpticalState != currentOpticalState) {
if (currentOpticalState == LOW) {
Serial.println("Beam BLOCKED");
} else {
Serial.println("Beam UNBLOCKED");
}
lastOpticalState = currentOpticalState;
}
delay(10);
}
Trying to get down to what could be the issue, I tried the mcp23xx_button example:
#include <Adafruit_MCP23X17.h>
#define BUTTON_PIN 1 // MCP23XXX pin button is attached to
Adafruit_MCP23X17 mcp;
void setup() {
Serial.begin(9600);
//while (!Serial);
Serial.println("MCP23xxx Button Test!");
// uncomment appropriate mcp.begin
if (!mcp.begin_I2C()) {
//if (!mcp.begin_SPI(CS_PIN)) {
Serial.println("Error.");
while (1);
}
// configure pin for input with pull up
mcp.pinMode(BUTTON_PIN, INPUT_PULLUP);
Serial.println("Looping...");
}
void loop() {
// LOW = pressed, HIGH = not pressed
if (!mcp.digitalRead(BUTTON_PIN)) {
Serial.println("Button Pressed!");
delay(250);
}
}
but I only ever get
02:20:40.177 -> MCP23xxx Button Test!
02:20:42.196 -> Error.
Which I do not understand why even this is not working, leading me to think that I am misunderstanding something very simple. I feel like I've read every post in the last decade about the MCP23017 but lack the programming knowledge to understand interfacing with it directly. The simple button sketch not working drove me to make my own post in hopes that I can get to the bottom of this.
Thank you