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In previously published articles we discussed about oscilloscope and also kit to build oscilloscope. Logic analyzer is another tool which somewhat used for production grade checking of circuits. Ordinary users do not need dedicated oscilloscope, a multimeter should serve most purposes. Here is a Basic Arduino Oscilloscope, Which Will Show Plotting on Serial Plotter of Arduino IDE and Analog Inputs Work as 6 Channels. This project we found on Arduino Project Hub :
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https://create.arduino.cc/projecthub/Meeker6751/arduino-oscilloscope-6-channel-674166 |
There is another such project published on Instructables :
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https://www.instructables.com/id/Another-Arduino-Oscilloscope/ |
How to Create, Test This Basic Arduino Oscilloscope
This is practically a code dependent oscilloscope. Arduino boards have six analog inputs – A0, A1, A2, A3, A4, A5. One need to check the code and set the adjustable variables, then run the sketch. Then open the serial plotter of Arduino IDE. On Arduino web IDE, you’ll find serial plotter under tool’s menu.
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This sketch will simulates a 6 channel oscilloscope. The input at the analog pins expected be be between 0 volt and 5 volts, with a maximum frequency of 1 KHz. Adjustable variables are within the code. This oscilloscope runs in two modes:
Continuous
Triggered
The criterion is further conditioned in code by whether it is increasing or decreasing. In triggered mode the total sweep time may be set in milliseconds. The beginning of a triggered sweep is indicated when the timing mark spikes to 5 Volt. The builtin LED (which is on-board LED, usually at pin 13) is an indicator of the oscilloscope states – (1) ON : continuous mode, sweeping in triggered mode
(2) Blinking : armed in triggered mode
(3) Off : all operations paused (by push button).
A push button can be connected to ground and digital pin 12 as optional component. When push button will be pressed, signal sampling and sweep will be stopped. Here is the code, it is heaving commented for helping the users :
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/* File: Oscilloscope.ino Title: Standalone Arduino 6 channel Triggered Oscilloscope Author: Meeker6751 Verson: 2018.4.23 Method: (0) Set the adjustable variables, (1) run the sketch (2) activate the serial plotter. Description: This sketch simulates a 6 beam oscilloscope. It is expected that the input(s) presented at the analog pins will be between 0 and 5 volts with a maximum frequency of 1 KHz. The adjustable variables are declared in a separate section. These variables can be found after the define statements. 1-6 beams may be selected which display voltages at A0-A5, respectively. Open analog pins produce spurious voltages. The oscilloscope runs in 2 modes: 'continuous' (free running) and 'triggered' (start sweep when a criterion is met. The triggering criterion is met when the input signal read off od A0 crosses over a predefined triggering voltage. The criterion is further conditioned by whether it is 'rising' or 'falling' when it crosses the predefined voltage. In triggered mode the total sweep time may be set in milliseconds. The beginning of a triggered sweep is indicated when the timing mark spikes to 5 vdc. When sweeping, the analog pin(s) will be sampled every 'SampleInterval' milliseconds. At the bottom of the plot, timing marks (a square wave) will be toggled every 10th 'SampleInterval' milliseconds. When more than 1 signal is being sampled, the signal displays may be 'superimposed' or 'channeled'. When channels are used, the voltages on the vertical axis are not calibrated. The builtin LED (pin 13) is an indicator of the oscilloscope state: (1) On, continuous mode or sweeping in triggered mode; (2) blinking, Armed in triggered mode, (3) Off, all operations paused (by push button). Optionally a push button, can be connected to ground and digital pin 12. When pressed, signal sampling and sweep are stopped. Pressing the push button again resumes the sweep (but with a gap in the signal trace(s)). The order of the plotted line legend is: timing marks (blue), trigger level (red, if in triggered mode), analog signals A0-A6, respectively (multi colored). */ #define ul unsigned long #define armed true // trigger and pushbutton state #define continuous true // sweep mode (free running) #define falling false // trigger slope positive #define rising true // trigger slope negative #define triggered false // sweep mode (sweep starts when triggered) #define sweeping false // sweeping for TriggeredSweepInterval msecs #define superimposed true // signals superimposed on display #define channeled false // signals channeled on display // adjustable variables int Beams = 6; // number of beams read bool DisplayMode = channeled; // 'superimposed' or 'channeled' ul SampleInterval = 200; // units: msecs * 10; 0.1 <= SampleInterval bool SweepMode = triggered; // 'continuous' or 'triggered' ul TriggeredSweepInterval = 40000; // total sweep time, units: seconds * 10,000 float TriggerDirection = rising; // 'rising' or 'falling' float TriggerVolts = 3.5; // trigger vdc; 0 <= TriggerVolts <= 5 // interrupt controlled variables ul LastSample = -1; // initially, no last sample bool LED = HIGH; int BlinkCount = 0; ul SweepCount = 0; // counts up to Sweep Interval bool Tick = false; // set to true when TickCount = SampleRate ul TickCount = 0; // counts up to SampleRate bool TimingMark; // toggles every 10th 'Sample Intewrval' ul TimingMarkCount = 0; // counts up to SampleInterval * 10 bool TriggerState; // 'armed' or 'sweeping' bool TriggerOnset = false; // marks first tick after trigger occurs // loop procedure variables float ChannelFloor; float ChannelHeight; bool freeze = false; // true: stop; false: run int PBPin = 12; // grounded push button on pin 12 (optional) int PBLastState = HIGH; // LOW (pressed) or HIGH (released) int PBVal; // inverse logic, push button tied to ground float ChannelScale; // proportion og signal to display float TriggerDisplay; // vertical position of trigger int TriggerLevel; // calculated from 'TriggerVolts' float Value; void interruptSetup() { noInterrupts(); // generate an interrupt every 0.1 msec TCCR2A = 2; // clear timer on compare, OCR2 TCCR2B = 2; // 16,000,000Hz/8=2,000,000 Hz; T2 clock ticks every 0.0005 msecs OCR2A = 199; // interrupt = 0.0005*200 = 0.1 msec TIMSK2 = 2; // set the ISR COMPA vect interrupts(); } ISR(TIMER2_COMPA_vect) { // interrupt every 0.1 msecs if (TickCount < SampleInterval) { TickCount++; BlinkCount++; if (BlinkCount >= 500) { BlinkCount = 0.0; LED = !LED; // toggle LED every 50 msecs } } else { // 'SampleInterval' has elapsed Tick = true; TickCount = 0; TimingMarkCount++; // update Timing mark if (TimingMarkCount >= 10) { // 10th 'SDampleInterval' has occurred TimingMark = !TimingMark; TimingMarkCount = 0; } if (SweepMode == triggered) { if (TriggerState == sweeping) { // sweeping, update sweep time SweepCount += SampleInterval; if (SweepCount >= TriggeredSweepInterval) { // sweep complete TriggerState = armed; LastSample = -1; } } else { // armed, look for trigger Value = analogRead(A0); if (LastSample > 0 and ((TriggerDirection == rising and Value >= TriggerLevel and LastSample < TriggerLevel) or (TriggerDirection == falling and Value <= TriggerLevel and LastSample > TriggerLevel))) { TriggerState = sweeping; // triggered SweepCount = 0; TriggerOnset = true; TimingMarkCount = 0; TimingMark = true; } LastSample = Value; } } } } void setup() { pinMode (LED_BUILTIN, OUTPUT); pinMode(PBPin, INPUT); // connected to a grounded push button digitalWrite(PBPin, HIGH); // pullup push button pin Serial.begin(115200); if (SweepMode == continuous) { TriggerState = sweeping; } else { TriggerState = armed; } TriggerLevel = (TriggerVolts / 5.0 ) * 1023; ChannelHeight = 5.0 / Beams; ChannelScale = 5.0 / 1024.0 / Beams; TriggerDisplay = TriggerVolts * ChannelScale + 5.0 - ChannelHeight; interruptSetup(); } void loop() { if (freeze) { digitalWrite(LED_BUILTIN, LOW); } else if (TriggerState == armed) { digitalWrite(LED_BUILTIN, LED); } else { digitalWrite(LED_BUILTIN, HIGH); } PBVal = digitalRead(PBPin); if (PBVal == LOW and PBLastState == HIGH) { // falling edge freeze = !freeze; delay (2); // ignore contact bounce } PBLastState = PBVal; if (!freeze and TriggerState == sweeping) { if (Tick) { // sample if Sample Interval msecs have elapsed if (TimingMark) { // display timing marks and trigger, if present if (TriggerOnset) { Serial.print(5.0); TriggerOnset = false; } else { Serial.print(0.1); } } else { Serial.print(0.0); } Serial.print(" "); ChannelFloor = 5.0 - ChannelHeight; // display trigger level, if applicable if (SweepMode == triggered) { Serial.print(TriggerLevel * ChannelScale + ChannelFloor); Serial.print (" "); } for (int AnalogPin = 0; AnalogPin <= Beams - 1; AnalogPin++) { // sample 1-6 analog signals and display them Value = analogRead(AnalogPin); Value = Value * ChannelScale + ChannelFloor; Serial.print(Value); Serial.print(" "); ChannelFloor -= ChannelHeight; } Tick = false; Serial.println(""); } } } |
