What I wanted to learn, and why it interested me: I wanted to learn how to use a motion detector, and use it as the signal to print text through a thermal receipt printer. It's interesting to me because so many automative processes are triggered by motion in daily life, specifically motion of human body, like the water fountain for example. A thermal receipt printer interests me because it outputs something physical and that I can manipulate the text to make it personal. 

Final outcome: A thermal receipt printer printing out a text for my roommate, triggered by human motion. 

When motion is detected by the Passive Infrared Sensor, the Thermal Receipt Printer prints a note for my roommate, which says "Hello roommate, Hello roommate, Good morning roommate, Have a nice day roommate."

Process and reflection: 

I started exploring the thermal receipt printer by printing the test page and checking what baud rate my printer is. Then, I wired up two buttons, one triggers the printer to print a short poem, the other triggers the printer to print an image of a house. It was really fun to see the possibility of printing images. However, images with high resolution couldn't be printed, I had to compress my images. 

After understanding how to use one component as the digital input trigger to signalize the thermal receipt printer to print, all I had to do was to replace it with the passive infrared sensor. The HIGH/LOW OUTPUT of the sensor goes into the Arduino and then acts as an input to tell the printer whether to print or not. One of the things that I had to ask AI for help was whether the sensor PIN is an INPUT_PULLUP, or just INPUT. I set it to be INPUT_PULLUP so that it "pulls" the pin's voltage up to a steady HIGH state by default.

Everything went pretty smooth with the help of online resources and some AI. I just have to keep reminding myself to understand things that I'm copying from AI. 

#include "Adafruit_Thermal.h"

#include "adalogo.h"

#include "adaqrcode.h"

#include "SoftwareSerial.h"

#define TX_PIN 6 // Arduino transmit  YELLOW WIRE  labeled RX on printer

#define RX_PIN 5 // Arduino receive   GREEN WIRE   labeled TX on printer

#define SENSOR_PIN 7 // connects to the infrared sensor signal

SoftwareSerial mySerial(RX_PIN, TX_PIN); // Declare SoftwareSerial obj first

Adafruit_Thermal printer(&mySerial);     // Pass addr to printer constructor

void setup() {

 pinMode(SENSOR_PIN, INPUT_PULLUP); // (inspired by Gemini)

 mySerial.begin(9600);  // Initialize SoftwareSerial

 //Serial1.begin(19200); // Use this instead if using hardware serial

 printer.begin();        // Init printer (same regardless of serial type)

 printer.setDefault(); // Restore printer to defaults

}

void loop() {

 if (digitalRead(SENSOR_PIN) == LOW) { // (inspired by Gemini)

   printer.wake();      

   delay(100);            // (inspired by Gemini)

   printer.reset();       // (inspired by Gemini)

   printer.setDefault();  // (inspired by Gemini)

   printer.println(F("Hello roommate,"));

   printer.println(F("Hello roommate,"));

   printer.println(F("Good morning rooommate,"));

   printer.println(F("Have a nice day roommate."));

   printer.feed(3);     

   printer.sleep();

   delay(10000); // (inspired by Gemini)

 }

}