How To Make Mini Oscilloscope

Oscilloscopes display the change of an electrical signal over time, with voltage and time as the Y- and X-axes, respectively, on a calibrated scale. The waveform can then be analyzed for properties such as amplitude, frequency, rise time, time interval, distortion, and others. Modern digital instruments may calculate and display these properties directly. Originally, calculation of these values required manually measuring the waveform against the scales built into the screen of the instrument

Diagram:

Code:

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <avr/pgmspace.h>               // PROGMEM
#include <EEPROM.h>

#define SCREEN_WIDTH 128                // OLED display width
#define SCREEN_HEIGHT 64                // OLED display height
#define REC_LENGTH 200                  // 

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1      // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

//
const char vRangeName[10][5] PROGMEM = {"A50V", "A 5V", " 50V", " 20V", " 10V", "  5V", "  2V", "  1V", "0.5V", "0.2V"}; // \0
const char * const vstring_table[] PROGMEM = {vRangeName[0], vRangeName[1], vRangeName[2], vRangeName[3], vRangeName[4], vRangeName[5], vRangeName[6], vRangeName[7], vRangeName[8], vRangeName[9]};
const char hRangeName[8][6] PROGMEM = {" 50ms", " 20ms", " 10ms", "  5ms", "  2ms", "  1ms", "500us", "200us"};          // (48
const char * const hstring_table[] PROGMEM = {hRangeName[0], hRangeName[1], hRangeName[2], hRangeName[3], hRangeName[4], hRangeName[5], hRangeName[6], hRangeName[7]};

int waveBuff[REC_LENGTH];      //  (RAM)
char chrBuff[10];              // 
String hScale = "xxxAs";
String vScale = "xxxx";

float lsb5V = 0.0055549;       // 5V0.005371 V/1LSB
float lsb50V = 0.051513;       // 50V 0.05371

volatile int vRange;           //   0:A50V, 1:A 5V, 2:50V, 3:20V, 4:10V, 5:5V, 6:2V, 7:1V, 8:0.5V
volatile int hRange;           // 0:50m, 1:20m, 2:10m, 3:5m, 4;2m, 5:1m, 6:500u, 7;200u
volatile int trigD;            // 0:1:
volatile int scopeP;           //  0:, 1:, 2:
volatile boolean hold = false; // 
volatile boolean paraChanged = false; //  true
volatile int saveTimer;        // EEPROM
int timeExec;                  // (ms)

int dataMin;                   // (min:0)
int dataMax;                   // (max:1023)
int dataAve;                   // 10 max:10230)
int rangeMax;                  // 
int rangeMin;                  // 
int rangeMaxDisp;              // max100
int rangeMinDisp;              // min
int trigP;                     // 
boolean trigSync;              // 
int att10x;                    // 1

void setup() {
  pinMode(2, INPUT_PULLUP);    // (int0
  pinMode(8, INPUT_PULLUP);    // Select
  pinMode(9, INPUT_PULLUP);    // Up
  pinMode(10, INPUT_PULLUP);   // Down
  pinMode(11, INPUT_PULLUP);   // Hold 
  pinMode(12, INPUT);          // 1/10
  pinMode(13, OUTPUT);         // 

  //     Serial.begin(115200);        // RAM
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x64
    //       Serial.println(F("SSD1306 failed"));
    for (;;);                               // Don't proceed, loop forever
  }
  loadEEPROM();                             // EEPROM
  analogReference(INTERNAL);                // ADC1.1Vvref)
  attachInterrupt(0, pin2IRQ, FALLING);     // 
  startScreen();                            // 
}

void loop() {
  digitalWrite(13, HIGH);
  setConditions();                          // RAM40
  readWave();                               //  (1.6ms )
  digitalWrite(13, LOW);                    //
  dataAnalize();                            // (0.4-0.7ms)
  writeCommonImage();                       // (4.6ms)
  plotData();                               // (5.4ms+)
  dispInf();                                // (6.2ms)
  display.display();                        // (37ms)
  saveEEPROM();                             // EEPROM
  while (hold == true) {                    // Hold
    dispHold();
    delay(10);
  }
}

void setConditions() {   // 
  // PROGMEM
  strcpy_P(chrBuff, (char*)pgm_read_word(&(hstring_table[hRange])));  // 
  hScale = chrBuff;                                                   // hScale

  // 
  strcpy_P(chrBuff, (char*)pgm_read_word(&(vstring_table[vRange])));  // 
  vScale = chrBuff;                                                   // vScale

  switch (vRange) {              // 
    case 0: {                    // Auto50V
        //        rangeMax = 1023;
        //        rangeMin = 0;
        att10x = 1;              // 
        break;
      }
    case 1: {                    // Auto 5V
        //        rangeMax = 1023;
        //        rangeMin = 0;
        att10x = 0;              // 
        break;
      }
    case 2: {                    // 50V
        rangeMax = 50 / lsb50V;  // 
        rangeMaxDisp = 5000;     // 100
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 1;              // 
        break;
      }
    case 3: {                    // 20V
        rangeMax = 20 / lsb50V;  // 
        rangeMaxDisp = 2000;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 1;              // 
        break;
      }
    case 4: {                    // 10V
        rangeMax = 10 / lsb50V;  // 
        rangeMaxDisp = 1000;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 1;              // 
        break;
      }
    case 5: {                    // 5V
        rangeMax = 5 / lsb5V;    // 
        rangeMaxDisp = 500;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 0;              // 
        break;
      }
    case 6: {                    // 2V
        rangeMax = 2 / lsb5V;    // 
        rangeMaxDisp = 200;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 0;              // 
        break;
      }
    case 7: {                    // 1V
        rangeMax = 1 / lsb5V;    // 
        rangeMaxDisp = 100;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 0;              // 
        break;
      }
    case 8: {                    // 0.5V
        rangeMax = 0.5 / lsb5V;  // 
        rangeMaxDisp = 50;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 0;              // 
        break;
      }
    case 9: {                    // 0.5V
        rangeMax = 0.2 / lsb5V;  // 
        rangeMaxDisp = 20;
        rangeMin = 0;
        rangeMinDisp = 0;
        att10x = 0;              // 
        break;
      }
  }
}

void writeCommonImage() {     // 
  display.clearDisplay();                   // (0.4ms)
  display.setTextColor(WHITE);              // 
  display.setCursor(86, 0);                 // Start at top-left corner
  display.println(F("av    V"));            // 1
  display.drawFastVLine(26, 9, 55, WHITE);  // 
  display.drawFastVLine(127, 9, 55, WHITE); // 

  display.drawFastHLine(24, 9, 7, WHITE);   // Max
  display.drawFastHLine(24, 36, 2, WHITE);  //
  display.drawFastHLine(24, 63, 7, WHITE);  //

  display.drawFastHLine(51, 9, 3, WHITE);   // Max
  display.drawFastHLine(51, 63, 3, WHITE);  //

  display.drawFastHLine(76, 9, 3, WHITE);   // Max
  display.drawFastHLine(76, 63, 3, WHITE);  //

  display.drawFastHLine(101, 9, 3, WHITE);  // Max
  display.drawFastHLine(101, 63, 3, WHITE); //

  display.drawFastHLine(123, 9, 5, WHITE);  // Max
  display.drawFastHLine(123, 63, 5, WHITE); // 

  for (int x = 26; x <= 128; x += 5) {
    display.drawFastHLine(x, 36, 2, WHITE); // ()
  }
  for (int x = (127 - 25); x > 30; x -= 25) {
    for (int y = 10; y < 63; y += 5) {
      display.drawFastVLine(x, y, 2, WHITE); // 3
    }
  }
}

void readWave() {                            // 
  if (att10x == 1) {                         // 1/10
    pinMode(12, OUTPUT);                     // 
    digitalWrite(12, LOW);                   // LOW
  } else {                                   // 
    pinMode(12, INPUT);                      // Hi-z
  }

  switch (hRange) {                          // 

    case 0: {                                // 50ms
        timeExec = 400 + 50;                 // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x07;              // 128 (arduino
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 112s
          delayMicroseconds(1888);           // 
        }
        break;
      }

    case 1: {                                // 20ms
        timeExec = 160 + 50;                 // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x07;              // 128 (arduino
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 112s
          delayMicroseconds(688);            // 
        }
        break;
      }

    case 2: {                                // 10 ms
        timeExec = 80 + 50;                  // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x07;              // 128 (arduino
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 112s
          delayMicroseconds(288);            // 
        }
        break;
      }

    case 3: {                                // 5 ms
        timeExec = 40 + 50;                  // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x07;              // 128 (arduino
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 112s
          delayMicroseconds(88);             // 
        }
        break;
      }

    case 4: {                                // 2 ms
        timeExec = 16 + 50;                  // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x06;              // 64 (0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 56s
          delayMicroseconds(24);             // 
        }
        break;
      }

    case 5: {                                // 1 ms
        timeExec = 8 + 50;                   // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x05;              // 16 (0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 28s
          delayMicroseconds(12);             // 
        }
        break;
      }

    case 6: {                                // 500us
        timeExec = 4 + 50;                   // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x04;              // 16(0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
        for (int i = 0; i < REC_LENGTH; i++) {     // 200
          waveBuff[i] = analogRead(0);       // 16s
          delayMicroseconds(4);              // 
          // 1.875snop 110.0625s @16MHz)
          asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop");
          asm("nop"); asm("nop"); asm("nop");
        }
        break;
      }

    case 7: {                                // 200us
        timeExec = 2 + 50;                   // (ms) EEPROM
        ADCSRA = ADCSRA & 0xf8;              // 3
        ADCSRA = ADCSRA | 0x02;              // :4(0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
        for (int i = 0; i < REC_LENGTH; i++) {
          waveBuff[i] = analogRead(0);       // 6s
          // 1.875snop 110.0625s @16MHz)
          asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop");
          asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop");
          asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop");
        }
        break;
      }
  }
}

void dataAnalize() {                   // 
  int d;
  long sum = 0;

  // 
  dataMin = 1023;                         // 
  dataMax = 0;                            // 
  for (int i = 0; i < REC_LENGTH; i++) {  // 
    d = waveBuff[i];
    sum = sum + d;
    if (d < dataMin) {                    // 
      dataMin = d;
    }
    if (d > dataMax) {                    // 
      dataMax = d;
    }
  }

  // 
  dataAve = (sum + 10) / 20;               // 10

  // max,min
  if (vRange <= 1) {                       // Auto1
    rangeMin = dataMin - 20;               // -20
    rangeMin = (rangeMin / 10) * 10;       // 10
    if (rangeMin < 0) {
      rangeMin = 0;                        // 0
    }
    rangeMax = dataMax + 20;               // +20
    rangeMax = ((rangeMax / 10) + 1) * 10; // 10
    if (rangeMax > 1020) {
      rangeMax = 1023;                     // 10201023
    }

    if (att10x == 1) {                            // 
      rangeMaxDisp = 100 * (rangeMax * lsb50V);   // ADC
      rangeMinDisp = 100 * (rangeMin * lsb50V);   // 
    } else {                                      // 
      rangeMaxDisp = 100 * (rangeMax * lsb5V);
      rangeMinDisp = 100 * (rangeMin * lsb5V);
    }
  } else {                                   // 
    // 
  }

  // 
  for (trigP = ((REC_LENGTH / 2) - 51); trigP < ((REC_LENGTH / 2) + 50); trigP++) { // 
    if (trigD == 0) {                        // 0
      if ((waveBuff[trigP - 1] < (dataMax + dataMin) / 2) && (waveBuff[trigP] >= (dataMax + dataMin) / 2)) {
        break;                              // 
      }
    } else {                                // 0
      if ((waveBuff[trigP - 1] > (dataMax + dataMin) / 2) && (waveBuff[trigP] <= (dataMax + dataMin) / 2)) {
        break;
      }                                    // 
    }
  }
  trigSync = true;
  if (trigP >= ((REC_LENGTH / 2) + 50)) {  // 
    trigP = (REC_LENGTH / 2);
    trigSync = false;                      // Unsync
  }
}

void startScreen() {                 // 
  display.clearDisplay();
  display.setTextSize(1);            // 2
  display.setTextColor(WHITE);       //
  display.setCursor(10, 25);         //
  display.println(F("EASY TECH"));   // 
  display.setCursor(10, 45);         //
  display.println(F("Mini OscilLoscope"));
  display.display();                 // 
  delay(5000);
  display.clearDisplay();
  display.setTextSize(1);            // 
}

void dispHold() {                            // Hold
  display.fillRect(32, 12, 24, 8, BLACK);    // 4
  display.setCursor(32, 12);
  display.print(F("Hold"));                  // Hold 
  display.display();                         //
}

void dispInf() {                             // 
  float voltage;
  // 
  display.setCursor(2, 0);                   // 
  display.print(vScale);                     // 
  if (scopeP == 0) {                         // 
    display.drawFastHLine(0, 7, 27, WHITE);  // 
    display.drawFastVLine(0, 5, 2, WHITE);
    display.drawFastVLine(26, 5, 2, WHITE);
  }

  // 
  display.setCursor(34, 0);                  //
  display.print(hScale);                     // (time/div)
  if (scopeP == 1) {                         // 
    display.drawFastHLine(32, 7, 33, WHITE); // 
    display.drawFastVLine(32, 5, 2, WHITE);
    display.drawFastVLine(64, 5, 2, WHITE);
  }

  // 
  display.setCursor(75, 0);                  // 
  if (trigD == 0) {
    display.print(char(0x18));               // 
  } else {
    display.print(char(0x19));               //               
  }
  if (scopeP == 2) {      // 
    display.drawFastHLine(71, 7, 13, WHITE); // 
    display.drawFastVLine(71, 5, 2, WHITE);
    display.drawFastVLine(83, 5, 2, WHITE);
  }

  // 
  if (att10x == 1) {                         // 10
    voltage = dataAve * lsb50V / 10.0;       // 50V
  } else {
    voltage = dataAve * lsb5V / 10.0;        // 5V
  }
  dtostrf(voltage, 4, 2, chrBuff);           // x.xx 
  display.setCursor(98, 0);                  // 
  display.print(chrBuff);                    // 
  //  display.print(saveTimer);                  // 

  // 
  voltage = rangeMaxDisp / 100.0;            // Max
  if (vRange == 1 || vRange > 4) {           // 5VAuto5V
    dtostrf(voltage, 4, 2, chrBuff);         //  *.** 
  } else {                                   //
    dtostrf(voltage, 4, 1, chrBuff);         // **.* 
  }
  display.setCursor(0, 9);
  display.print(chrBuff);                    // Max

  voltage = (rangeMaxDisp + rangeMinDisp) / 200.0; // 
  if (vRange == 1 || vRange > 4) {           // 5VAuto5V
    dtostrf(voltage, 4, 2, chrBuff);         // 2
  } else {                                   //
    dtostrf(voltage, 4, 1, chrBuff);         // 1
  }
  display.setCursor(0, 33);
  display.print(chrBuff);                    // 

  voltage = rangeMinDisp / 100.0;            // Min
  if (vRange == 1 || vRange > 4) {           // 5VAuto5V
    dtostrf(voltage, 4, 2, chrBuff);         // 2
  } else {
    dtostrf(voltage, 4, 1, chrBuff);         // 1
  }
  display.setCursor(0, 57);
  display.print(chrBuff);                    // Min

  // 
  if (trigSync == false) {                   // 
    display.setCursor(60, 55);               // 
    display.print(F("Unsync"));              // Unsync 
  }
}

void plotData() {                    // 
  long y1, y2;
  for (int x = 0; x <= 98; x++) {
    y1 = map(waveBuff[x + trigP - 50], rangeMin, rangeMax, 63, 9); // 
    y1 = constrain(y1, 9, 63);                                     // 
    y2 = map(waveBuff[x + trigP - 49], rangeMin, rangeMax, 63, 9); //
    y2 = constrain(y2, 9, 63);                                     //
    display.drawLine(x + 27, y1, x + 28, y2, WHITE);               // 
  }
}

void saveEEPROM() {                    // EEPROM
  if (paraChanged == true) {           // 
    saveTimer = saveTimer - timeExec;  // 
    if (saveTimer < 0) {               // 
      paraChanged = false;             // 
      EEPROM.write(0, vRange);        // 
      EEPROM.write(1, hRange);
      EEPROM.write(2, trigD);
      EEPROM.write(3, scopeP);
    }
  }
}

void loadEEPROM() {                // EEPROM
  int x;
  x = EEPROM.read(0);             // vRange
  if ((x < 0) || (x > 9)) {        // 0-9
    x = 3;                         // 
  }
  vRange = x;

  x = EEPROM.read(1);             // hRange
  if ((x < 0) || (x > 7)) {        // 0-9
    x = 3;                         // 
  }
  hRange = x;
  x = EEPROM.read(2);             // trigD
  if ((x < 0) || (x > 1)) {        // 0-9
    x = 1;                         // 
  }
  trigD = x;
  x = EEPROM.read(3);             // scopeP
  if ((x < 0) || (x > 2)) {        // 0-9
    x = 1;                         // 
  }
  scopeP = x;
}

void pin2IRQ() {                   // Pin2(int0)
  //pin8,9,10,11Pin2
  //

  int x;                           // 
  x = PINB;                        // B

  if ( (x & 0x07) != 0x07) {       // 3High
    saveTimer = 5000;              // EEPROM(ms
    paraChanged = true;            // ON
  }

  if ((x & 0x01) == 0) {
    scopeP++;
    if (scopeP > 2) {
      scopeP = 0;
    }
  }

  if ((x & 0x02) == 0) {           // UP
    if (scopeP == 0) {             // 
      vRange++;
      if (vRange > 9) {
        vRange = 9;
      }
    }
    if (scopeP == 1) {             // 
      hRange++;
      if (hRange > 7) {
        hRange = 7;
      }
    }
    if (scopeP == 2) {             // 
      trigD = 0;                   // 
    }
  }

  if ((x & 0x04) == 0) {           // DOWN
    if (scopeP == 0) {             // 
      vRange--;
      if (vRange < 0) {
        vRange = 0;
      }
    }
    if (scopeP == 1) {             // 
      hRange--;
      if (hRange < 0) {
        hRange = 0;
      }
    }
    if (scopeP == 2) {             // 
      trigD = 1;                   // 
    }
  }

  if ((x & 0x08) == 0) {           // HOLD
    hold = ! hold;                 // 
  }
}