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sagar saini
Published © GPL3+

Arduino Nano 20KHz pocket sized Digital Oscilloscope

A difficult code with a try to display waveform on a small screen with precisions. Volts-time, frequency, duty cycle and divisions.

IntermediateWork in progress1 hour28,047
Arduino Nano 20KHz pocket sized Digital Oscilloscope

Things used in this project

Hardware components

Arduino Nano R3
Arduino Nano R3
×1
0.96" OLED 64x128 Display Module
ElectroPeak 0.96" OLED 64x128 Display Module
×1

Software apps and online services

EasyEDA
JLCPCB EasyEDA
Arduino IDE
Arduino IDE

Hand tools and fabrication machines

Breadboard, 830 Tie Points
Breadboard, 830 Tie Points
10 Pc. Jumper Wire Kit, 5 cm Long
10 Pc. Jumper Wire Kit, 5 cm Long

Story

Read more

Schematics

circuit PDF

Code

code

C/C++
// Follow us on Hackster, Hackaday and the Instructables.
//Please First uncomment/comment the oled driver lines, which you are using
//Circuitkicker.com -- Sagar saini --sainisagar7294

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
//#include <Adafruit_SH1106.h>            // https://github.com/wonho-maker/Adafruit_SH1106
#include <EEPROM.h>

#define SCREEN_WIDTH   128              // OLED display width
#define SCREEN_HEIGHT   64              // OLED display height
#define REC_LENG       200              // size of wave data buffer
#define DISP_LENG      100              // size of display data
#define MIN_TRIG_SWING   5              // minimum trigger swing.(Display "Unsync" if swing smaller than this value
#define DOTS_DIV        25

// 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 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);   // device name is oled
//Adafruit_SH1106 oled(OLED_RESET);        // use this when SH1106

#define R_12k   4        //  12k ohm
#define R_820k  16       //  820k ohm  for AC low range
#define R_82k   17       //  82k omm for AC Hi range

// Range name table (those are stored in flash memory)
const char vRangeName[10][5] PROGMEM = {"A50V", "A 5V", " 50V", " 20V", " 10V", "  5V", "  2V", "  1V", "0.5V", "0.2V"}; // Vertical display character (number of characters including \ 0 is required)
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[22][6] PROGMEM = {"200ms", "100ms", " 50ms", " 20ms", " 10ms", "  5ms", "  2ms", "  1ms", "500us", "200us", "100us", " 50us", " 81us", " 41us", " 20us", "156us", " 78us", " 31us", "15.6u", "7.8us", "3.1us", "1.56u"};  //  Hrizontal display characters
const char * const hstring_table[] PROGMEM = {hRangeName[0], hRangeName[1], hRangeName[2], hRangeName[3], hRangeName[4], hRangeName[5], hRangeName[6], hRangeName[7], hRangeName[8], hRangeName[9],
    hRangeName[10], hRangeName[11], hRangeName[12], hRangeName[13], hRangeName[14], hRangeName[15], hRangeName[16], hRangeName[17], hRangeName[18], hRangeName[19], hRangeName[20], hRangeName[21]};
const float hRangeValue[] PROGMEM = { 0.2, 0.1, 0.05, 0.02, 0.01, 0.005, 0.002, 0.001, 0.5e-3, 0.2e-3, 0.2e-3, 0.2e-3, 81.3e-6, 81.3e-6, 81.3e-6, 156.25e-6, 78.125e-6, 31.25e-6, 15.625e-6, 7.8125e-6, 3.125e-6, 1.5625e-6}; // record speed in second. ( = 25pix on screen) this value used for freq calc.

int waveBuff[REC_LENG];        // wave form buffer (RAM remaining capacity is barely)
char chrBuff[8];               // display string buffer
char hScale[] = "xxxAs";       // horizontal scale character
char vScale[] = "xxxx";        // vartical scale

float lsb5V    = 0.00563965;   // (5V)sensivity coefficient of 5V range. std=0.00563965 1.1*630/(1024*120)
float lsb50V   = 0.0512939;    // (50V)sensivity coefficient of 50V range. std=0.0512939 1.1*520.91/(1024*10.91)

float lsb5Vac  = 0.00630776;   //  std=0.00630776 V/LSB
float lsb50Vac = 0.0579751;    //  std=0.0579751 V/LSB

volatile int vRange;           // V-range number                   2:50V,  3:20V,  4:10V,  5:5V,  6:2V,  7:1V,  8:0.5V,  9:0.2V
volatile int hRange;           // H-range nubmer 0:200ms, 1:100ms, 2:50ms, 3:20ms, 4:10ms, 5:5ms, 6;2ms, 7:1ms, 8:500us, 9:200us, 10:100us, 11:50us, 12:
volatile int trigD;            // trigger slope flag,     0:positive 1:negative
volatile int scopeP;           // operation scope position number. 0:Veratical, 1:Hrizontal, 2:Trigger slope, 3:DC/AC/FFT
volatile boolean hold = false; // hold flag
volatile boolean switchPushed = false; // flag of switch pusshed !
volatile int saveTimer;        // remaining time for saving EEPROM
int timeExec;                  // approx. execution time of current range setting (ms)

int dataMin;                   // buffer minimum value (smallest=0)
int dataMax;                   //        maximum value (largest=1023)
int dataAve;                   // 10 x average value (use 10x value to keep accuracy. so, max=10230)
int dataRms;                   // 10x rms. value
int rangeMax;                  // buffer value to graph full swing
int rangeMin;                  // buffer value of graph botto
int rangeMaxDisp;              // display value of max. (100x value)
int rangeMinDisp;              // display value if min.
int trigP;                     // trigger position pointer on data buffer
boolean trigSync;              // flag of trigger detected
int att10x;                    // 10x attenuator ON (effective when 1)
int inMode;                    //  0=DC+, 1=DC+-, 2=AC
int offset5Vac;
int offset50Vac;

float waveFreq;                // frequency (Hz)
float waveDuty;                // duty ratio (%)

#include <fix_fft.h>
#define FFT_N 128
volatile boolean fftMode = false; // FFT mode false:Wave, true:FFT

void setup() {
  pinMode(2, INPUT_PULLUP);             // reserve (button press interrupt (int.0 IRQ))
  pinMode(3, OUTPUT);                   // PWM for trigger level
  pinMode(R_12k, INPUT);                // pin4 1/10 attenuator(Off=High-Z, Enable=Output Low)
  pinMode(5, INPUT_PULLUP);             // FFT mode
  pinMode(7, INPUT_PULLUP);             // AC mode
  pinMode(8, INPUT_PULLUP);             // Select button
  pinMode(9, INPUT_PULLUP);             // Up
  pinMode(10, INPUT_PULLUP);            // Calibration pulse output
  pinMode(11, INPUT_PULLUP);            // Hold
  pinMode(12, INPUT_PULLUP);            // Down
  pinMode(13, OUTPUT);                  // LED
  pinMode(R_820k, INPUT);               // A2
  pinMode(R_82k, INPUT);                // A3
  DIDR0 = 0x0f;                         // disable digital input buffer of A0-A3

  oled.begin(SSD1306_SWITCHCAPVCC, 0x3C); // select 3C or 3D (set your OLED I2C address)
 // oled.begin(SH1106_SWITCHCAPVCC, 0x3C);  // use this when SH1106

  auxFunctions();                       // Voltage measure (never return)
  loadEEPROM();                         // read last settings from EEPROM
#define REFERENCE_INTERNAL
#ifdef REFERENCE_INTERNAL
  analogReference(INTERNAL);            // ADC full scale = 1.1V
  trigger_level(26);                    // PWM triger level 0.5V for ET
#else
  analogReference(DEFAULT);             // ADC full scale = 5.0V
  trigger_level(128);                   // PWM triger level 2.5V for ET
#endif
  (void) analogRead(0);                 // dummy read to select A0 and reference
#ifdef USE_PIN2IRQ
  attachInterrupt(0, pin2IRQ, FALLING); // activate IRQ at falling edge mode
#else
  PCMSK0 = _BV(PCINT4) | _BV(PCINT3) | _BV(PCINT1) | _BV(PCINT0); // D8,D9,D12 pin change interrupt
  PCICR  = _BV(PCIE0);                  // enable interrupt from PCIE0 group
#endif
  startScreen();                        // display start message
}

void loop() {
  if (hRange < 15) pulse();             // calibration pulse is for realtime sampling only
  setInputOffset();                     // coupling mode set(AC/DC)
  setConditions();                      // set measurment conditions
  digitalWrite(13, HIGH);               // flash LED
  readWave();                           // read wave form and store into buffer memory
  digitalWrite(13, LOW);                // stop LED
  setConditions();                      // set measurment conditions again (reflect change during measure)
  dataAnalize();                        // analize data
  writeCommonImage();                   // write fixed screen image (2.6ms)
  plotData();                           // plot waveform (10-18ms)
  dispInf();                            // display information (6.5-8.5ms)
  oled.display();                       // send screen buffer to OLED (37ms)
  saveEEPROM();                         // save settings to EEPROM if necessary
  while (hold == true) {                // wait if Hold flag ON
    dispHold();
    if (inMode > 0) {                   //  if DC mode,
      if (acZero() == 1) {              //  if offset adj. executed
        scopeP = 0;                     //  scope position to vartical
        hold = false;                   //  cancel hold
      }
      delay(10);
    }                                   //
  }
}

int acZero() {                         // cancel AC renge offset
  if (digitalRead(8) == LOW) {         //  if select pushed
    if (vRange >= 5) {                 //  = 5V or less
      offset5Vac = dataAve / 10;       // adjust the offset
    } else {                           // range more than 5V
      offset50Vac = dataAve / 10;      //  adjust the offset
    }
    saveEEPROM();                      // 
    return 1;                          //  adjusted
  }
  return 0;                            // no adjust
}

void setInputOffset() {                //  set offset circuit
  if (inMode >= 1) {                   //  if AC mode
    if (att10x == 1) {                 //  10X-att enabled
      pull5V(R_82k);                   //  pull 5V by 82k
      hiZ(R_820k);
    } else {                           //  10X-att disable
      hiZ(R_82k);
      pull5V(R_820k);                  //  pull 5V by 820k
    }
  } else {                             //  DC mode
    hiZ(R_820k);                       // Hi-Z
    hiZ(R_82k);                        // Hi-Z
  }
}

void hiZ(int n) {                      // set the pin to hi-z
  pinMode(n, INPUT);                   // set INPUT
  digitalWrite(n, LOW);                //  no pull up
}

void pull5V(int n) {                   //  pull 5V through registor 
  pinMode(n, OUTPUT);                  //  set OUTPUT
  digitalWrite(n, HIGH);               //  OUTPUT HIGH
}

void pullGND(int n) {                  //  pull GND through registor 
  pinMode(n, OUTPUT);                  //  set OUTPUT
  digitalWrite(n, LOW);                //  output LOW
}

void setConditions() {              //  measuring condition setting
  if (digitalRead(7) == LOW) {      // set AC/DC
    inMode = 1;                     // 
  } else {
    inMode = 0;                     // 
  }

  // get range name from PROGMEM
  strcpy_P(hScale, (char*)pgm_read_word(&(hstring_table[hRange])));  // H range name
  strcpy_P(vScale, (char*)pgm_read_word(&(vstring_table[vRange])));  // V range name

  switch (vRange) {                // setting of Vrange
    case 0:                        // delaeted Auto50V range
      att10x = 1;                  // use input attenuator
      break;

    case 1:                        // delaeted Auto 5V range
      att10x = 0;                  // no attenuator
      break;

    case 2:                        // 50V range
      if (inMode == 0) {
        rangeMax = 50.0 / lsb50V;  // set full scale pixcel count number
        rangeMaxDisp = 5000;       // vartical scale (set100x value)
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset50Vac + 25.0 / lsb50Vac; // set full scale pixcel count number
        rangeMaxDisp = 2500;       // vartical scale (set100x value)
        rangeMin = offset50Vac - 25.0 / lsb50Vac;
        rangeMinDisp = -2500;
      }
      att10x = 1;                  // use input attenuator
      break;

    case 3:                        // 20V range
      if (inMode == 0) {
        rangeMax = 20.0 / lsb50V;  // set full scale pixcel count number
        rangeMaxDisp = 2000;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset50Vac + 10.0 / lsb50Vac;  // set full scale pixcel count number
        rangeMaxDisp = 1000;
        rangeMin = offset50Vac - 10.0 / lsb50Vac;
        rangeMinDisp = -1000;
      }
      att10x = 1;                  // use input attenuator
      break;

    case 4:                        // 10V range
      if (inMode == 0) {
        rangeMax = 10.0 / lsb50V;  // set full scale pixcel count number
        rangeMaxDisp = 1000;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset50Vac + 5.0 / lsb50Vac;  // set full scale pixcel count number
        rangeMaxDisp = 500;
        rangeMin = offset50Vac - 5.0 / lsb50Vac;
        rangeMinDisp = -500;
      }
      att10x = 1;                  // use input attenuator
      break;

    case 5:                        // 5V range
      if (inMode == 0) {
        rangeMax = 5.0 / lsb5V;    // set full scale pixcel count number
        rangeMaxDisp = 500;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset5Vac + 2.5 / lsb5Vac;    // set full scale pixcel count number
        rangeMaxDisp = 250;
        rangeMin = offset5Vac - 2.5 / lsb5Vac;
        rangeMinDisp = -250;
      }
      att10x = 0;                  // no input attenuator
      break;

    case 6:                        // 2V range
      if (inMode == 0) {
        rangeMax = 2.0 / lsb5V;    // set full scale pixcel count number
        rangeMaxDisp = 200;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset5Vac + 1.0 / lsb5Vac;    // set full scale pixcel count number
        rangeMaxDisp = 100;
        rangeMin = offset5Vac - 1.0 / lsb5Vac;
        rangeMinDisp = -100;
      }
      att10x = 0;                  // no input attenuator
      break;

    case 7:                        // 1V range
      if (inMode == 0) {
        rangeMax = 1.0 / lsb5V;    // set full scale pixcel count number
        rangeMaxDisp = 100;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset5Vac + 0.5 / lsb5Vac;    // set full scale pixcel count number
        rangeMaxDisp = 50;
        rangeMin = offset5Vac - 0.5 / lsb5Vac;
        rangeMinDisp = -50;
      }
      att10x = 0;                  // no input attenuator
      break;

    case 8:                        // 0.5V range
      if (inMode == 0) {
        rangeMax = 0.5 / lsb5V;    // set full scale pixcel count number
        rangeMaxDisp = 50;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset5Vac + 0.25 / lsb5Vac;  // set full scale pixcel count number
        rangeMaxDisp = 25;
        rangeMin = offset5Vac - 0.25 / lsb5Vac;
        rangeMinDisp = -25;
      }
      att10x = 0;                  // no input attenuator
      break;

    case 9:                        // 0.2V range
      if (inMode == 0) {
        rangeMax = 0.2 / lsb5V;    // set full scale pixcel count number
        rangeMaxDisp = 20;
        rangeMin = 0;
        rangeMinDisp = 0;
      } else {
        rangeMax = offset5Vac + 0.1 / lsb5Vac;  // set full scale pixcel count number
        rangeMaxDisp = 10;
        rangeMin = offset5Vac - 0.1 / lsb5Vac;
        rangeMinDisp = -10;
      }
      att10x = 0;                  // no input attenuator
      break;
  }
}

void writeCommonImage() {                 //  Common screen image drawing
  oled.clearDisplay();                    //  erase all(0.4ms)
  if (fftMode == true) return;            // no need for the FFT display
  oled.setTextColor(WHITE);               // write in white character
  oled.drawFastVLine(26, 9, 55, WHITE);   // left vartical line
  oled.drawFastVLine(127, 9, 3, WHITE);   // right vrtical line up
  oled.drawFastVLine(127, 61, 3, WHITE);  // right vrtical line bottom

  oled.drawFastHLine(24, 9, 7, WHITE);    // Max value auxiliary mark
  oled.drawFastHLine(24, 36, 2, WHITE);
  oled.drawFastHLine(24, 63, 7, WHITE);

  oled.drawFastHLine(51, 9, 3, WHITE);    // Max value auxiliary mark
  oled.drawFastHLine(51, 63, 3, WHITE);

  oled.drawFastHLine(76, 9, 3, WHITE);    // Max value auxiliary mark
  oled.drawFastHLine(76, 63, 3, WHITE);

  oled.drawFastHLine(101, 9, 3, WHITE);   // Max value auxiliary mark
  oled.drawFastHLine(101, 63, 3, WHITE);

  oled.drawFastHLine(123, 9, 5, WHITE);   // right side Max value auxiliary mark
  oled.drawFastHLine(123, 63, 5, WHITE);

  for (int x = 26; x <= 128; x += 5) {
    oled.drawFastHLine(x, 36, 2, WHITE);  // Draw the center line (horizontal line) with a dotted line
  }
  for (int x = (127 - 25); x > 30; x -= 25) {
    for (int y = 10; y < 63; y += 5) {
      oled.drawFastVLine(x, y, 2, WHITE); // Draw 3 vertical lines with dotted lines
    }
  }
}

void readWave() {                          //  Record waveform to memory array
  byte *p = (byte *) waveBuff;
  if (att10x == 1) {                       // if 1/10 attenuator required
    pullGND(R_12k);
  } else {                                 // if not required
    hiZ(R_12k);
  }
  switchPushed = false;                    // Clear switch operation flag

  switch (hRange) {                        // set recording conditions in accordance with the range number
    case 0:                                // 200ms range
      timeExec = 1600 + 60;                // Approximate execution time(ms) Used for countdown until saving to EEPROM
      sample_us(200000L);
      break;

    case 1:                                // 100ms range
      timeExec = 800 + 60;                 // Approximate execution time(ms) Used for countdown until saving to EEPROM
      sample_us(100000L);
      break;

    case 2:                                // 50ms range
      timeExec = 400 + 60;                 // Approximate execution time(ms)
      sample_us(50000L);
      break;

    case 3:                                // 20ms range
      timeExec = 160 + 60;                 // Approximate execution time(ms)
      sample_us(20000L);
      break;

    case 4:                                // 10ms range
      timeExec = 80 + 60;                  // Approximate execution time(ms)
      sample_us(10000L);
      break;

    case 5:                                // 5ms range
      timeExec = 40 + 60;                  // Approximate execution time(ms)
      sample_us(5000L);
      break;

    case 6:                                // 2ms range
      timeExec = 16 + 60;                  // Approximate execution time(ms)
      ADCSRA = (ADCSRA & 0xf8) | 0x06;     // dividing ratio = 64 (0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
      for (int i = 0; i < REC_LENG; i++) { // up to rec buffer size
        waveBuff[i] = analogRead(0);       // read and save approx 56us
        delayMicroseconds(23);             // timing adjustmet tuned
      }
      break;

    case 7:                                // 1ms range
      timeExec = 8 + 60;                   // Approximate execution time(ms)
      ADCSRA = (ADCSRA & 0xf8) | 0x05;     // dividing ratio = 16 (0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
      for (int i = 0; i < REC_LENG; i++) { // up to rec buffer size
        waveBuff[i] = analogRead(0);       // read and save approx 28us
        delayMicroseconds(11);             // timing adjustmet tuned
      }
      break;

    case 8:                                // 500us range
      timeExec = 4 + 60;                   // Approximate execution time(ms)
      ADCSRA = (ADCSRA & 0xf8) | 0x04;     // dividing ratio = 16(0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
      for (int i = 0; i < REC_LENG; i++) { // up to rec buffer size
        waveBuff[i] = analogRead(0);       // read and save approx 16us
        delayMicroseconds(4);              // timing adjustmet
        // time fine adjustment 0.0625 x 8 = 0.5usnop=0.0625us @16MHz)
        asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop"); asm("nop");
      }
      break;

    case 9:
    case 10:
    case 11:                               //  common 200, 100, 50us range
      timeExec = 2 + 60;                   // Approximate execution time(ms)
      ADCSRA = (ADCSRA & 0xf8) | 0x02;     // dividing ratio = 4(0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
      for (int i = 0; i < REC_LENG; i++) { // up to rec buffer size
        waveBuff[i] = analogRead(0);       // read and save approx 6us
        // time fine adjustment 0.0625 * 20 = 1.25us (nop=0.0625us @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");
      }
      break;

    case 12:                               // full speed, ADC free run. 81.25us/div 308ksps
    case 13:                               // x2 40.625us/div
    case 14:                               // x4 20.3125us/div
      timeExec = 1 + 60;                   // Approximate execution time(ms)
      ADCSRB = 0x40;                       // Auto Trigger free run
      ADCSRA = (ADCSRA & 0xf8) | 0x62;     // Auto Trigger Enable. dividing ratio = 4(0x1=2, 0x2=4, 0x3=8, 0x4=16, 0x5=32, 0x6=64, 0x7=128)
      cli();                               //  no interrupt for TIMING
      for (int i = 0; i < REC_LENG; i++) {
        while ((ADCSRA & 0x10) == 0);      // polling until adif==1
        ADCSRA |= 0x10;                    // clear ADIF bit so that ADC can do next operation
        *p++ = ADCL;                       // must read adch low byte first
        *p++ = ADCH;                       // read adch high byte
      }
      ADCSRA = ADCSRA & 0x9f;              // stop ADC free run ADSC=0 ADATE=0
      sei();                               // no interrupt for TIMING
      break;
    case 15:                               // 156.25us/div equivalent time sampling
    case 16:                               // 78.125us/div equivalent time sampling
    case 17:                               // 31.25us/div equivalent time sampling
    case 18:                               // 15.625us/div equivalent time sampling
    case 19:                               // 7.8125us/div equivalent time sampling
    case 20:                               // 3.125us/div equivalent time sampling
    case 21:                               // 1.5625us/div equivalent time sampling
      extern byte oscspeed;
      timeExec = 2 + 60;                   // Approximate execution time(ms)
      oscspeed = 21 - hRange;              // oscspeed = 6...0
      modeequiv();
      break;
  }
}

void dataAnalize() {                       //  get various information from wave form
  long d;
  long sum = 0;

  // search max and min value
  dataMin = 1023;                          // min value initialize to big number
  dataMax = 0;                             // max value initialize to small number
  for (int i = 0; i < REC_LENG; i++) {     // serach max min value
    d = waveBuff[i];
    sum = sum + d;
    if (d < dataMin) {                     // update min
      dataMin = d;
    }
    if (d > dataMax) {                     // updata max
      dataMax = d;
    }
  }

  // calculate average
  dataAve = (sum + 10) / 20;               // Average value calculation (calculated by 10 times to improve accuracy)

  //  rms value calc.
  sum = 0;
  for (int i = 0; i < REC_LENG; i++) {     //  to all buffer
    d = waveBuff[i] - (dataAve + 5) / 10;  // (10
    sum += d * d;                          // 
  }
  dataRms = sqrt(sum / REC_LENG);          // 10 get rms value

  // Trigger position search
  for (trigP = (DISP_LENG / 2); trigP < (REC_LENG - 1 - (DISP_LENG / 2)); trigP++) { // Find the points that straddle the median at the center  50 of the data range
    if (trigD == 0) {                             // if trigger direction is positive
      if ((waveBuff[trigP - 1] < (dataMax + dataMin) / 2) && (waveBuff[trigP] >= (dataMax + dataMin) / 2)) {
        break;                                    // positive trigger position found !
      }
    } else {                                      // trigger direction is negative
      if ((waveBuff[trigP - 1] > (dataMax + dataMin) / 2) && (waveBuff[trigP] <= (dataMax + dataMin) / 2)) {
        break;
      }                                           // negative trigger poshition found !
    }
  }
#ifdef ET_NATIVE_TRIGGER
  if (hRange > 14)
    trigP = 50;     // equivalent time sampling use delayed trigger
#endif
  trigSync = true;
  if (trigP >= ((REC_LENG / 2) + (DISP_LENG / 2))) {  // If the trigger is not found in range
    trigP = (REC_LENG / 2);                       // Set it to the center for the time being
    trigSync = false;                             // set Unsync display flag
  }
  if ((dataMax - dataMin) <= MIN_TRIG_SWING) {    // amplitude of the waveform smaller than the specified value
    trigSync = false;                             // set Unsync display flag
  }
  freqDuty();
}

void freqDuty() {                               //  detect frequency and duty cycle value from waveform data
  int swingCenter;                              // center of wave (half of p-p)
  float p0 = 0;                                 // 1-st posi edge
  float p1 = 0;                                 // total length of cycles
  float p2 = 0;                                 // total length of pulse high time
  float pFine = 0;                              // fine position (0-1.0)
  float lastPosiEdge;                           // last positive edge position

  float pPeriod;                                // pulse period
  float pWidth;                                 // pulse width

  int p1Count = 0;                              // wave cycle count
  int p2Count = 0;                              // High time count

  boolean a0Detected = false;
  //  boolean b0Detected = false;
  boolean posiSerch = true;                     // true when serching posi edge

  swingCenter = (3 * (dataMin + dataMax)) / 2;  // calculate wave center value

  for (int i = 1; i < REC_LENG - 2; i++) {      // scan all over the buffer
    if (posiSerch == true) {   // posi slope (frequency serch)
      if ((sum3(i) <= swingCenter) && (sum3(i + 1) > swingCenter)) {  // if across the center when rising (+-3data used to eliminate noize)
        pFine = (float)(swingCenter - sum3(i)) / ((swingCenter - sum3(i)) + (sum3(i + 1) - swingCenter) );  // fine cross point calc.
        if (a0Detected == false) {              // if 1-st cross
          a0Detected = true;                    // set find flag
          p0 = i + pFine;                       // save this position as startposition
        } else {
          p1 = i + pFine - p0;                  // record length (length of n*cycle time)
          p1Count++;
        }
        lastPosiEdge = i + pFine;               // record location for Pw calcration
        posiSerch = false;
      }
    } else {   // nega slope serch (duration serch)
      if ((sum3(i) >= swingCenter) && (sum3(i + 1) < swingCenter)) {  // if across the center when falling (+-3data used to eliminate noize)
        pFine = (float)(sum3(i) - swingCenter) / ((sum3(i) - swingCenter) + (swingCenter - sum3(i + 1)) );
        if (a0Detected == true) {
          p2 = p2 + (i + pFine - lastPosiEdge); // calucurate pulse width and accumurate it
          p2Count++;
        }
        posiSerch = true;
      }
    }
  }

  pPeriod = p1 / p1Count;                 // pulse period
  pWidth  = p2 / p2Count;                 // palse width

  waveFreq = DOTS_DIV / ((pgm_read_float(hRangeValue + hRange) * pPeriod)); // frequency
  waveDuty = 100.0 * pWidth / pPeriod;                                      // duty ratio
}

int sum3(int k) {       // Sum of before and after and own value
  int m = waveBuff[k - 1] + waveBuff[k] + waveBuff[k + 1];
  return m;
}

void startScreen() {                      //  Staru up screen
  oled.clearDisplay();
//  oled.setTextSize(2);                  // at double size character
  oled.setTextColor(WHITE);
  oled.println(F("Oscilloscope"));       // Title(Poor Man's Osilloscope, RadioPench 1)
  oled.println(F("Sagar Saini"));          // this for SH1106
  oled.display();                         // actual display here
  delay(1500);
  oled.clearDisplay();
  oled.setTextSize(1);                    // After this, standard font size
}

void dispHold() {                         // display "Hold"
  oled.fillRect(42, 11, 24, 8, BLACK);    // black paint 4 characters
  oled.setCursor(42, 11);
  oled.print(F("Hold"));                  // Hold
  oled.display();                         //
}

void dispInf() {                          //   Display of various information
  float volt;
  // DC/AC display DC/AC couple mode
  oled.setCursor(1, 0);
#ifndef UNDERLINE_SCOPE
  if (scopeP == 3) {                      // if scoped
    oled.setTextColor(BLACK, WHITE);
  }
#endif
  if (fftMode == true) {
    oled.print(F("FF"));
  } else if (inMode == 0) {
    oled.print(F("DC"));
  } else {
    oled.print(F("AC"));
  }
#ifndef UNDERLINE_SCOPE
  oled.setTextColor(WHITE);
#else
  if (scopeP == 3) {                      // if scoped
    oled.drawFastHLine(0, 7, 14, WHITE); // display scoped mark at the bottom
    oled.drawFastVLine(0, 5,  2, WHITE);
    oled.drawFastVLine(13, 5,  2, WHITE);
  }
#endif

  //  vertical sensitivity
  oled.setCursor(15, 0);                  // around top left
  oled.print(vScale);                     // vertical sensitivity value
  if (scopeP == 0) {                      // if scoped
    oled.drawFastHLine(13, 7, 27, WHITE); // display scoped mark at the bottom
    oled.drawFastVLine(13, 5,  2, WHITE);
    oled.drawFastVLine(39, 5,  2, WHITE);
  }

  //  horizontal sweep speed
  oled.setCursor(42, 0);                  //
  oled.print(hScale);                     // display sweep speed (time/div)
  if (scopeP == 1) {                      // if scoped
    oled.drawFastHLine(40, 7, 33, WHITE); // display scoped mark
    oled.drawFastVLine(40, 5,  2, WHITE);
    oled.drawFastVLine(72, 5,  2, WHITE);
  }
  if (hRange > 14 && fftMode == false) {  // if equivalent time sampling
    oled.setCursor(0, 21);                //
    oled.print(F("ET"));
  }

  //  trigger polarity
  oled.setCursor(75, 0);                  // at top center
  if (trigD == 0) {                       // if positive
    oled.print(char(0x18));               // up mark
  } else {
    oled.print(char(0x19));               // down mark              
  }
  if (scopeP == 2) {                      // if scoped
    oled.drawFastHLine(72, 7, 11, WHITE); // display scoped mark
    oled.drawFastVLine(72, 5,  2, WHITE);
    oled.drawFastVLine(82, 5,  2, WHITE);
  }

  // average voltage
  if (inMode == 0) {                      // DC if DC mode
    oled.setCursor(86, 0);
    oled.print(F("av"));                  // av : average
    if (att10x == 1) {                    // if 10x attenuator is used
      volt = dataAve * lsb50V / 10.0;     // 50V(10) range value
    } else {                              // no!
      volt = dataAve * lsb5V / 10.0;      // 5V 10range value
    }
    if (volt < 9.995) {                   // if less than 10V
      dtostrf(volt, 4, 2, chrBuff);       // format x.xx
    } else {                              // no! over 10
      dtostrf(volt, 4, 1, chrBuff);       // format xx.x
    }
  } else {                                // AC  AC mode
    oled.setCursor(86, 0);
    oled.print(F("rm"));                  // rm : rms root mean square

    if (att10x == 1) {                    // if 10x attenuator is used
      volt = dataRms * lsb50Vac;          //  50V range value
    } else {                              // no!
      volt = dataRms * lsb5Vac;           // 5V range value
    }

    if (volt < 9.995) {                   // if less than 10V
      dtostrf(volt, 4, 2, chrBuff);       // format x.xx
    } else {                              // no!
      dtostrf(volt, 4, 1, chrBuff);       // format xx.x
    }
  }
  oled.setCursor(98, 0);                  // at top right
  oled.print(chrBuff);                    //  display voltage 
  oled.print(F("V"));

  //  display frequency, duty % or trigger missed
  if (trigSync == false) {                // If trigger point can't found
    oled.fillRect(92, 14, 24, 8, BLACK);  // black paint 4 character
    oled.setCursor(92, 14);               //
    oled.print(F("unSync"));              // display Unsync
  } else {
    oled.fillRect(91, 12, 25, 9, BLACK);  // erase Freq area
    oled.setCursor(92, 13);               // set display location
    if (waveFreq < 9.9995) {              // if less than 9.9995Hz
      oled.print(waveFreq, 2);            // display 9.99Hz
      oled.print(F("Hz"));
    } else if (waveFreq < 99.995) {       // if less than 99.995Hz
      oled.print(waveFreq, 1);            // display 99.9Hz
      oled.print(F("Hz"));
    } else if (waveFreq < 999.95) {       // if less than 999.95Hz
      oled.print(waveFreq, 1);            // display 999.9H
      oled.print(F("H"));
    } else if (waveFreq < 9995.0) {       // if less than 9.995kHz
      oled.print((waveFreq / 1000.0), 2); // display 9.99kH
      oled.print(F("kH"));
    } else if (waveFreq < 99950.0) {      // if less than 99.95kHz                         // if more
      oled.print((waveFreq / 1000.0), 1); // display 99.9kH
      oled.print(F("kH"));
    } else {                              // if more
      oled.print((waveFreq / 1000.0), 0); // display 999kHz
      oled.print(F("kHz"));
    }
    oled.fillRect(97, 21, 25, 10, BLACK); // erase Freq area (as small as possible)
    oled.setCursor(98, 23);               // set location
    oled.print(waveDuty, 1);              // display duty (High level ratio) in %
    oled.print(F("%"));
  }

  //  vartical scale lines
  if (fftMode == true) return;            // no need for the FFT display
  volt = rangeMaxDisp / 100.0;            // convert Max voltage
  if (vRange <= 3) {                      // 20V if range is 20 or more
    dtostrf(volt, 4, 0, chrBuff);         // format **
  } else {
    if (vRange <= 7) {
      dtostrf(volt, 4, 1, chrBuff);       // format **.*
    } else {
      dtostrf(volt, 4, 2, chrBuff);       // format *.**
    }
  }
  oled.setCursor(0, 9);
  oled.print(chrBuff);                    //  display Max value

  volt = (rangeMaxDisp + rangeMinDisp) / 200.0; // center value calculation
  if (vRange <= 3) {                      // 20V
    dtostrf(volt, 4, 0, chrBuff);         // format **20
  } else {
    if (vRange <= 7) {
      dtostrf(volt, 4, 1, chrBuff);       // format **.*
    } else {
      dtostrf(volt, 4, 2, chrBuff);       // format *.**
    }
  }
  oled.setCursor(0, 33);
  oled.print(chrBuff);                    //  display the value

  volt = rangeMinDisp / 100.0;            //  convart Min voltage
  if (vRange <= 3) {                      // 20V
    dtostrf(volt, 4, 0, chrBuff);         // format **20
  } else {
    if (vRange <= 7) {
      dtostrf(volt, 4, 1, chrBuff);       // format **.*
    } else {
      dtostrf(volt, 4, 2, chrBuff);       // format *.**
      if (inMode >= 1 ) {                 // 0.5 0.2V  compress zero(-0.25 -> -.25)
        chrBuff[1] = chrBuff[2];          //  
        chrBuff[2] = chrBuff[3];
        chrBuff[3] = chrBuff[4];
        chrBuff[4] = chrBuff[5];
      }
    }
  }
  oled.setCursor(0, 57);
  oled.print(chrBuff);                    //  display the value
  //  this for debug (value display on screen)
  //  oled.fillRect(40, 12, 25, 9, BLACK);    //  
  //  oled.setCursor(40, 13);                 //
  //  oled.print(hRange);                     // 
}

void plotData() {                    //  plot waveform on OLED
  long y1, y2;
  if (fftMode == true) {                            // FFT
      plotFFT();
  } else if (hRange <= 9 || hRange == 12 || hRange > 14) {          //  noromal plot
    for (int x = 0; x <= 98; x++) {
      y1 = map(waveBuff[x + trigP - 50], rangeMin, rangeMax, 63, 9); // convert to plot address
      y1 = constrain(y1, 9, 63);                                     // Crush(Saturate) the protruding part
      y2 = map(waveBuff[x + trigP - 49], rangeMin, rangeMax, 63, 9); // to address calucurate
      y2 = constrain(y2, 9, 63);                                     //
      oled.drawLine(x + 27, y1, x + 28, y2, WHITE);                  // connect between point
    }
  } else if (hRange == 10 || hRange == 13) {         // 100us2 zoom 2X when 100us range
    for (int x = 0; x <= 49; x++) {
      y1 = map(waveBuff[x + trigP - 25], rangeMin, rangeMax, 63, 9); // convert to plot address
      y1 = constrain(y1, 9, 63);                                     // Crush(Saturate) the protruding part
      y2 = map(waveBuff[x + trigP - 24], rangeMin, rangeMax, 63, 9); // to address calucurate
      y2 = constrain(y2, 9, 63);                                     //
      oled.drawLine(x * 2 + 27, y1, x * 2 + 29, y2, WHITE);              // connect between point
    }
  } else if (hRange == 11 || hRange == 14) {        // 50us4 zoom 4x when 50us range
    for (int x = 0; x <= 24; x++) {
      y1 = map(waveBuff[x + trigP - 13], rangeMin, rangeMax, 63, 9); // convert to plot address
      y1 = constrain(y1, 9, 63);                                     // Crush(Saturate) the protruding part
      y2 = map(waveBuff[x + trigP - 12], rangeMin, rangeMax, 63, 9); // to address calucurate
      y2 = constrain(y2, 9, 63);                                     //
      oled.drawLine(x * 4 + 27, y1, x * 4 + 31, y2, WHITE);              // connect between point
    }
  }
}

void saveEEPROM() {                    // Save the setting value in EEPROM after waiting a while after the button operation.
  if (saveTimer > 0) {                 // If the timer value is positive,
    saveTimer = saveTimer - timeExec;  // Timer subtraction
    if (saveTimer < 0) {               // if time up
      EEPROM.write(0, vRange);         // save current status to EEPROM
      EEPROM.write(1, hRange);
      EEPROM.write(2, trigD);
      EEPROM.write(3, scopeP);
      EEPROM.write(4, offset5Vac >> 8);    // AC5V(
      EEPROM.write(5, offset5Vac & 0xFF);  // 
      EEPROM.write(6, offset50Vac >> 8);   //      50V                  
      EEPROM.write(7, offset50Vac & 0xFF); //                           
    }
  }
}

void loadEEPROM() {                    // Read setting values from EEPROM (abnormal values will be corrected to default)
  int x;
  x = EEPROM.read(0);                  // vRange
  if ((x < 0) || (x > 9)) {            // if out side 0-9
    x = 5;                             // default value
  }
  vRange = x;

  x = EEPROM.read(1);                  // hRange
  if ((x < 0) || (x > 21)) {           // if out of 0-21
    x = 3;                             // default value
  }
  hRange = x;
  x = EEPROM.read(2);                  // trigD
  if ((x < 0) || (x > 1)) {            // if out of 0-1
    x = 1;                             // default value
  }
  trigD = x;
  x = EEPROM.read(3);                  // scopeP
  if ((x < 0) || (x > 3)) {            // if out of 0-3
    x = 1;                             // default value
  }
  scopeP = x;

  x = EEPROM.read(4);                  // AC 5V offset value of AC5V
  x = x << 8 ;
  x = x | EEPROM.read(5);
  if ((x < 350) || (x > 650 )) {       //  350-650if abnormal value,
    x = 594;                           //  default value
  }
  offset5Vac = x;

  x = EEPROM.read(6);                  //AC 50V offset value of AC50V
  x = x << 8 ;
  x = x | EEPROM.read(7);
  if ((x < 350) || (x > 650 )) {       //  (350-650) if abnormal value,
    x = 546;                           //  default value
  }
  offset50Vac = x;
}

void auxFunctions() {                     //  select AUX function
  if (digitalRead(8) == LOW) {            //  if SELECT button pushed, measure battery voltage
    battVolt();
  }
  if (digitalRead(9) == LOW) {            // UP  DMM5V
    dmm5V();
  }
  if (digitalRead(12) == LOW) {           // DOWN DMM50V
    dmm50V();
  }
}

void battVolt() {                         //  Battery voltage measure (this for pen osillo)
  float volt;
  long x;
  analogReference(DEFAULT);               // ADC full scale set to Vcc
  while (1) {                             // do forever
    x = 0;
    for (int i = 0; i < 100; i++) {       // 100 times
      x = x + analogRead(1);              // A1read A1 pin voltage and accumulate
    }
    volt = (x / 100.0) * 5.0 / 1023.0;    // convert voltage value
    oled.clearDisplay();                  // all erase screen(0.4ms)
    oled.setTextColor(WHITE);             // write in white character
    oled.setCursor(20, 16);               //
    oled.setTextSize(1);                  // standerd size character
    oled.println(F("Battery voltage"));
    oled.setCursor(35, 30);               //
    oled.setTextSize(2);                  // double size character
    dtostrf(volt, 4, 2, chrBuff);         // display batterry voltage x.xxV
    oled.print(chrBuff);
    oled.println(F("V"));
    oled.display();
    delay(150);
  }
}

void dmm5V() {                             //  5V  digital voltmeter 5V range
  float volt, vPP;
  analogReference(INTERNAL);
  while (1) {                              // 
    digitalWrite(13, HIGH);                // flash LED
    oled.clearDisplay();                   // erase screen (0.4ms)
    oled.setTextColor(WHITE);              // write in white character
    oled.setCursor(0, 0);                  //
    oled.setTextSize(1);                   // by standerd size character

    if (digitalRead(7) == HIGH) {          // DC   if switch is DC mode
      hiZ(R_820k);                         //  set measure condition
      hiZ(R_82k);
      hiZ(R_12k);                          //
      volt = analogRead(0) * lsb5V;        // DC measure voltage
      oled.println(F("DC DVM 5V range"));  //
      oled.setCursor(20, 22);              //
      oled.setTextSize(2);                 // double size character
      dtostrf(volt, 4, 2, chrBuff);        // display voltage x.xxV
      oled.print(chrBuff);
      oled.print(F("V"));
    } else {                               // AC  AC mode
      pull5V(R_820k);                      // give offset
      hiZ(R_82k);
      hiZ(R_12k);                          // Set the attenuator control pin to Hi-z (use as input)

      ADCSRA = ADCSRA & 0xf8;              // clear bottom 3bit
      ADCSRA = ADCSRA | 0x07;              // dividing ratio = 128 (default of Arduino
      for (int i = 0; i < REC_LENG; i++) { // 5msrecoord to buffer at 5ms range settings
        waveBuff[i] = analogRead(0);       // read and save approx 112s
        delayMicroseconds(87);             // timing adjustmet tuned
      }
      dataAnalize();                       //  analize data

      volt = dataRms * lsb5Vac;            //  get RMS value
      vPP = (dataMax - dataMin) * lsb5Vac; // P-P get Peak to peak voltage

      oled.println(F("AC DVM 5V range"));
      oled.setTextSize(2);                 // double size character
      dtostrf(volt, 4, 2, chrBuff);        // foromat x.xx
      oled.setCursor(20, 16);              //
      oled.print(chrBuff);                 //  display rms voltage
      oled.println(F("Vrms"));
      dtostrf(vPP, 4, 2, chrBuff);         // format x.xx
      oled.setCursor(20, 38);              //
      oled.print(chrBuff);                 // P-P
      oled.println(F("Vpp"));
    }
    oled.display();                        //  actual display here
    digitalWrite(13, LOW);                 // stop LED flash
    delay(150);                            // wait next measure
  }
}

void dmm50V() {                            //  5V  digital voltmeter 5V range
  float volt, vPP;
  analogReference(INTERNAL);
  while (1) {                              // forever,
    digitalWrite(13, HIGH);                // flash LED
    oled.clearDisplay();                   // erase screen (0.4ms)
    oled.setTextColor(WHITE);              // write in white character
    oled.setCursor(0, 0);                  //
    oled.setTextSize(1);                   // by standerd size character

    if (digitalRead(7) == HIGH) {          // DC   if awitch is DC mode
      hiZ(R_820k);                         //  set measure condition
      hiZ(R_82k);
      pullGND(R_12k);                      //
      volt = analogRead(0) * lsb50V;       // DC measure voltage
      oled.println(F("DC DVM 50V range")); //
      oled.setCursor(20, 22);              //
      oled.setTextSize(2);                 // double size character
      dtostrf(volt, 4, 1, chrBuff);        // display voltage xx.xV
      oled.print(chrBuff);
      oled.print(F("V"));
    } else {                               // AC  AC mode
      hiZ(R_820k);                         //  set measure condition
      pull5V(R_82k);                       // pull up
      pullGND(R_12k);                      // att 10x

      ADCSRA = ADCSRA & 0xf8;              // clear bottom 3bit
      ADCSRA = ADCSRA | 0x07;              // dividing ratio = 128 (default of Arduino
      for (int i = 0; i < REC_LENG; i++) { // 5msrecoord to buffer at 5ms range settings
        waveBuff[i] = analogRead(0);       // read and save approx 112s
        delayMicroseconds(87);             // timing adjustmet tuned
      }
      dataAnalize();                       //  analize data

      volt = dataRms * lsb50Vac;            //  get RMS value
...

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Credits

sagar saini
81 projects • 85 followers
I am Sagar Saini an electronic hardware enthusiast

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