//tx_rx03  Robert Hart Mar 2019.
//https://roberthart56.github.io/SCFAB/SC_lab/Sensors/tx_rx_sensors/index.html

//Modified from Adrián´s Adrianino´s step response: https://fabacademy.org/2020/labs/leon/students/adrian-torres/adrianino.html#step
//Pin changes.
//Added digitalWriteFast.
//Added Oled screen output.

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);


long result;   //variable for the result of the tx_rx measurement.
int analog_pin = A2; //  PA2 of the ATtiny1614
int tx_pin = A1;  //     PA1 of the ATtiny1614
void setup() {
pinMode(tx_pin,OUTPUT);      //Pin 2 provides the voltage step
Serial.begin(115200);
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  delay(2000);
  display.clearDisplay();
  display.setTextColor(WHITE);
}


long tx_rx(){         //Function to execute rx_tx algorithm and return a value
                      //that depends on coupling of two electrodes.
                      //Value returned is a long integer.
  int read_high;
  int read_low;
  int diff;
  long int sum;
  int N_samples = 100;    //Number of samples to take.  Larger number slows it down, but reduces scatter.

  sum = 0;

  for (int i = 0; i < N_samples; i++){
   digitalWriteFast(tx_pin,HIGH);              //Step the voltage high on conductor 1.
   read_high = analogRead(analog_pin);        //Measure response of conductor 2.
   delayMicroseconds(100);            //Delay to reach steady state.
   digitalWriteFast(tx_pin,LOW);               //Step the voltage to zero on conductor 1.
   read_low = analogRead(analog_pin);         //Measure response of conductor 2.
   diff = read_high - read_low;       //desired answer is the difference between high and low.
 sum += diff;                       //Sums up N_samples of these measurements.
 }
  return sum;
}                         //End of tx_rx function.


void loop() {

result = tx_rx();
result = map(result, 19000, 50000, 0, 1024);  //I recommend mapping the values of the two copper plates, it will depend on their size
Serial.println(result);
delay(100);
delay(100);

   //clear display
  display.clearDisplay();
   
 if (result > 0)
 {// display 
  display.setTextSize(1);
  display.setCursor(0,0);
  display.print("OOPS TILTED!");
  display.setTextSize(2);}
  else 
 { // display 
  display.setTextSize(1);
  display.setCursor(0,0);
  display.print("Value:");
  display.setTextSize(2);
  display.setCursor(0,10);
  display.print(result);
  display.print("");}

  

  display.display(); 
}