thermostat

* Thermostat
#+CAPTION: The finished thermostat
#+NAME:   fig:Thermostat
[[./img/thermostat.jpeg]]

#+CAPTION: The innards
#+NAME:   fig:Thermostat Innards
[[./img/thermostat-back.jpeg]]

** Notes and Parts
*** Rotary Encoder
digikey part number: 118-PEC11R-4320F-S0012-ND
https://www.digikey.com/en/products/detail/bourns-inc/PEC11R-4320F-S0012/4699235?so=84473212&content=productdetail_US&mkt_tok=MDI4LVNYSy01MDcAAAGP7gCMSmK3S7iQMFn5oT0O7WjvWYwZCCJSnY_UqbFVAni8uOG82dcPK6wfp3T7Dy_SS-4I20sn1ZHBDY0ZDDaqZXyvshl6x9CQ6nFVvuls
*** Epoll
https://github.com/davecheney/gpio/blob/master/gpio_linux.go

*** Hardware Debounce
https://raspberrypi.stackexchange.com/questions/118349/what-is-the-proper-way-to-debounce-a-gpio-input
https://www.digikey.com/en/articles/how-to-implement-hardware-debounce-for-switches-and-relays
*** OLED
AZDelivery I2C 0.96-inch OLED Display • Compatible with Arduino SSD1306
& Raspberry Pi • Set of 3 • 128x64 Pixels IIC 3.3V 5V White Character
Screen Module
https://www.amazon.com/gp/product/B074N9VLZX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
*** Arduino Example
Rotary encoder decoding using two interrupt lines.
Most Arduino boards have two external interrupts,
numbers 0 (on digital pin 2) and 1 (on digital pin 3).

Program sketch is for SparkFun Rotary Encoder sku: COM-09117
Connect the middle pin of the three to ground.
The outside two pins of the three are connected to
digital pins 2 and 3

#+begin_src c
  volatile int number = 0;                // Testnumber, print it when it changes value,
                                          // used in loop and both interrupt routines
  int oldnumber = number;

  volatile boolean halfleft = false;      // Used in both interrupt routines
  volatile boolean halfright = false;

  void setup(){
    Serial.begin(9600);
    pinMode(2, INPUT);
    digitalWrite(2, HIGH);                // Turn on internal pullup resistor
    pinMode(3, INPUT);
    digitalWrite(3, HIGH);                // Turn on internal pullup resistor
    attachInterrupt(0, isr_2, FALLING);   // Call isr_2 when digital pin 2 goes LOW
    attachInterrupt(1, isr_3, FALLING);   // Call isr_3 when digital pin 3 goes LOW
  }

  void loop(){
    if(number != oldnumber){              // Change in value ?
      Serial.println(number);             // Yes, print it (or whatever)
      oldnumber = number;
    }
  }

  void isr_2(){                                              // Pin2 went LOW
    delay(1);                                                // Debounce time
    if(digitalRead(2) == LOW){                               // Pin2 still LOW ?
      if(digitalRead(3) == HIGH && halfright == false){      // -->
        halfright = true;                                    // One half click clockwise
      } 
      if(digitalRead(3) == LOW && halfleft == true){         // <--
        halfleft = false;                                    // One whole click counter-
        number--;                                            // clockwise
      }
    }
  }

  void isr_3(){                                             // Pin3 went LOW
    delay(1);                                               // Debounce time
    if(digitalRead(3) == LOW){                              // Pin3 still LOW ?
      if(digitalRead(2) == HIGH && halfleft == false){      // <--
        halfleft = true;                                    // One half  click counter-
      }                                                     // clockwise
      if(digitalRead(2) == LOW && halfright == true){       // -->
        halfright = false;                                  // One whole click clockwise
        number++;
      }
    }
  }
#+end_src