Make an Oscilloscope Using the SainSmart Mega2560 With the TFT LCD Shield and the 3.5 "color Touch Screen

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This instructable will show you how to build a portable Touch Screen
Oscilloscope for less than 40 U$!


The oscilloscope is one of the most powerful electronic instruments that
is available to electronics hobbyist, experimenters, and engineers. It is
mainly used to measue time-varying signals. Any time you have a signal
that varies with time( slowly, quickly, and /or periodically ) you can use
an oscilloscope to measure it , visualize it, and to find any unexpected
features in it.

We can use an oscilloscope to observe and study signal characteristics
that we could otherwise not see .

You will learn about the Arduino mega analog to digital converter( ADC).

We will be using the Arduino analog A0 input to sample and capture time
varying signals by Writing a program that will also display those signals
in a 3.8" TFT LCD touch display, and we will input data to modify the
oscilloscope behavior, using the touch capabilities of the screen display.

Before we start building and programming, lets review some basic
characteristics of an oscilloscope.

These are functions you can control on most oscilloscopes:

Sweep speed. Sweep speed is usually measured in units of time per distance,
like milliseconds/centimeter or milliseconds per division.This might also
be referred to as the horizontal sensitivity.

Vertical sensitivity. That's the measure of how sensitive the display dot
is to voltage applied to the input terminals. It is usually measured in
volts/centimeter or volts per division.

A trigger signal can be generated when the signal value reaches some
particular level - the trigger level. In most cases you can set the trigger
level to a voltage value of your choosing. A trigger is used to capture and
stabilize the waveform on the screen, or to wait for an event before
capturing the data
.
The oscilloscope, like my 4 channel DC DVM, will not be as accurate as
a commercial unit, but it works pretty good for low voltage and low frequencies.

Step 1: UPDATE: Sketch to Convert Oscope to 3 Channel DVM With Graphic Display + Lego Enclosure

Thank you to all who voted for me! This Instructable won 3rd prize in the Arduino contest, and first prize in the Gadget contest...

Included are pictures and code to convert your oscope to a 3 Channel DVM and to show the output of each channel individually in the scope display by pressing a soft key on the display. ( the third button from the top)

you will need an L shaped female pin connector if you want to have the flexibility of inserting jumpers, otherwise, just bend the pins on one side of the jumpers to insert them in the analog channels (A0- A3) to use them as your probes.

Just download the sketch and upload it to the Arduino.

You can label each channel individually, just change the wording in the sketch.

I have also made a lego enclosure for the scope..check out the pictures.

Step 2: Parts List

You will need :

Step 3: Build the Hardware.

Construction of the Oscilloscope is fairly simple. You just have to put the parts of the Sainsmart kit together. All you need to do is add two jumpers; one for ground, and the other to use as  your oscilloscope test probe.

You will need to bend the pins on one side of the jumper wires, and insert them into the A0 pin and GND pin of the Arduino (see pictures for detail),  before installing the display shield, as the display shield will cover the ports once it's in place. 

Plug  the Shield into the Arduino ,  then plug  the display into the shield, and you're done!!! 

Now let's  test the display before we turn it into an oscilloscope.

Step 4: The Software: UTFT Library Test.

If you finished putting your kit together, plug it into the USB cable that connects to your PC running the Arduino IDE.

If you haven't done so, download the UTFT and UTouch Libraries, and copy them to the libraries folder where you have the arduino IDE installed.

If the libraries installed properly, you will see the UTFT and the UTouch options when you click on the Files option, and scroll down to examples.

If the UTFT option is in your menu list, select it, then select arduino, and finally, UTFT_Demo_320x240. This will load the cool demo program.

With the program loaded in the IDE, scroll down to view the following code:

 // Uncomment the next line for Arduino 2009/Uno
//UTFT myGLCD(ITDB32S,19,18,17,16);   // Remember to change the model parameter to suit your display module!

// Uncomment the next line for Arduino Mega
UTFT myGLCD(ITDB32S,38,39,40,41);   // Remember to change the model parameter to suit your display module!


Comment out the command for the UNO , and uncomment the  command for the Mega ,as I did.

Now, go to the tools menu, click on board, and select  Arduino Mega 2560 or Mega ADK , if not already selected.

Click on verify to compile the program. If there are no errors, click on upload to  load and execute the program.

If everything is Ok, you will see a cool demo program running. Pictures in this step, show screenshots of the demo running.


Step 5: The Software: UTouch Library Test.

Now we need to test the Utouch  Library

Go to the files menu  and select ; Examples>UTouch>Arduino>Utouch_ButtonTest and load the program to the IDE.
Verify and  run the program.

You should see a keypad show up in the display, and, as you press the number keys, they should show up at the bottom of the screen.

If all went well, we are ready to load the Oscilloscope software.

Step 6: The Oscilloscope

Below, you will find the sketch for the Oscilloscope. Before we copy and paste the program, let's review some limitations and explain the program.

I've had to do a fair amount of research to come up with the code, and many snippets have been "borrowed" from several sources.

I divided the program into several subrutines to make it easier to understand. The code is well documented, but, if you have trouble understanding it, leave a comment and I'll try to explain it.

The Oscilloscope bandwidth is limited to about 1 khz, but there is room for improvement.

The input is limited to a 5volt peak to peak waveform, unless you use a voltage divider at the input, and also limited to positive waveforms from 0 to 5 volts.

I used some code I found at: http://www.microsmart.co.za/technical/2014/03/01/advanced-arduino-adc/ to adjust the ADC sample time.

The graphics and touch functions were modified, and borrowed, from the Henning Karlsen examples provided in his libraries.

I used a LM 317 voltage regulator, and a 555 IC timer as an astable ocillator, to create the signals used to test the oscilloscope input.

Hope you enjoyed reading and hopefully building this instructable. If you find it useful, please vote for me in the contests.

Note: I included the sKetch, the UTFT and the UTouch libraries in the libraries.zip file for those of you having trouble.

Copy and paste the sketch to your Arduino IDE

//----------------------START PROGRAM
/*--------------------------------------------------------------
Program: OscopetouchLCDmega

Description: Digital Oscilloscope with data displayed
on Color TFT LCD with touch screen

Hardware: sainsmart mega2560 board with 3.5" tft lcd touch module display and shield kit
http://www.sainsmart.com/home-page-view/sainsmart...

Software: Developed using Arduino 1.0.3 software
This program requires the UTFT library and the
UTouch library from Henning Karlsen.
web: http://www.henningkarlsen.com/electronics
Version 1.00
Date: 5 April 2014

Author: johnag
--------------------------------------------------------------*/

#include
#include
// Declare which fonts we will be using
extern uint8_t SmallFont[];
// Initialize Screen and touch functions
UTFT myGLCD(ITDB32S,38,39,40,41);
UTouch myTouch(6,5,4,3,2);
// Declare variables
char buf[12];
int x,y;
int Input = 0;
byte Sample[320];
byte OldSample[320];
int StartSample = 0;
int EndSample = 0;
int Max = 100;
int Min = 100;
int mode = 0;
int dTime = 1;
int tmode = 0;
int Trigger = 0;
int SampleSize = 0;
int SampleTime = 0;
int dgvh;
int hpos = 50; //set 0v on horizontal grid
int vsens = 4; // vertical sensitivity

// Define various ADC prescaler
const unsigned char PS_16 = (1 << ADPS2);
const unsigned char PS_32 = (1 << ADPS2) | (1 << ADPS0);
const unsigned char PS_64 = (1 << ADPS2) | (1 << ADPS1);
const unsigned char PS_128 = (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);

//------------Start Subrutines------------------------------------
//--------draw buttons sub
void buttons(){
myGLCD.setColor(0, 0, 255);
myGLCD.fillRoundRect (250, 1, 310, 50);
myGLCD.fillRoundRect (250, 55, 310, 105);
myGLCD.fillRoundRect (250, 110, 310, 160);
myGLCD.fillRoundRect (250, 165, 310, 215);
}
//-------touchscreen position sub
void touch(){
while (myTouch.dataAvailable())
{
myTouch.read();
x=myTouch.getX();
y=myTouch.getY();
delay(500);
if ((y>=1) && (y<=50)) // Delay row
{
if ((x>=250) && (x<=300)) // Delay Button
waitForIt(250, 1, 310, 50);
mode= mode ++ ;
{
myGLCD.setColor(255, 0, 0);
myGLCD.drawRoundRect (250, 1, 310, 50);
// Select delay times
if (mode == 0) dTime = 0;
if (mode == 1) dTime = 1;
if (mode == 2) dTime = 2;
if (mode == 3) dTime = 5;
if (mode == 4) dTime = 10;
if (mode == 5) dTime = 20;
if (mode == 6) dTime = 30;
if (mode == 7) dTime = 50;
if (mode == 8) dTime = 100;
if (mode == 9) dTime = 200;
if (mode == 10) dTime = 500;
if (mode > 10) mode = 0;


}}

if ((y>=70) && (y<=120)) // Trigger row
{
if ((x>=250) && (x<=300)) // Trigger Button
waitForIt(250, 55, 310, 105);
tmode= tmode ++;
{
myGLCD.setColor(255, 0, 0);
// Select Software trigger value
myGLCD.drawRoundRect (250, 55, 310, 105);
if (tmode == 1) Trigger = 0;
if (tmode == 2) Trigger = 10;
if (tmode == 3) Trigger = 20;
if (tmode == 4) Trigger = 30;
if (tmode == 5) Trigger = 50;
if (tmode > 5)tmode = 0;
}}
if ((y>=130) && (y<=180)) // H position row
{
if ((x>=250) && (x<=300)) // H position Button
waitForIt(250, 110, 310, 160);
hpos= hpos ++;

{
myGLCD.setColor(255, 0, 0);
myGLCD.drawRoundRect (250, 110, 310, 160);
myGLCD.clrScr();
buttons();
if (hpos > 60)hpos = 50;
}}}}
//----------wait for touch sub
void waitForIt(int x1, int y1, int x2, int y2)
{
while (myTouch.dataAvailable())
myTouch.read();
}
//----------draw grid sub
void DrawGrid(){

myGLCD.setColor( 0, 200, 0);
for( dgvh = 0; dgvh < 5; dgvh ++){
myGLCD.drawLine( dgvh * 50, 0, dgvh * 50, 240);
myGLCD.drawLine( 0, dgvh * 50, 245 ,dgvh * 50);
}
myGLCD.drawLine( 245, 0, 245, 240);
myGLCD.drawLine( 0, 239, 245, 239);
myGLCD.setColor(255, 255, 255);
myGLCD.drawRoundRect (250, 1, 310, 50);
myGLCD.drawRoundRect (250, 55, 310, 105);
myGLCD.drawRoundRect (250, 110, 310, 160);
myGLCD.drawRoundRect (250, 165, 310, 215);

}
// ------ Wait for input to be greater than trigger sub
void trigger(){

while (Input < Trigger){ Input = analogRead(A0)*5/100;
}}

//---------------End Subrutines ----------------------


void setup() {
myGLCD.InitLCD();
myGLCD.clrScr();
myTouch.InitTouch();
myTouch.setPrecision(PREC_MEDIUM);
buttons();
pinMode(0, INPUT);
// set up the ADC
ADCSRA &= ~PS_128; // remove bits set by Arduino library

// you can choose a prescaler from below.
// PS_16, PS_32, PS_64 or PS_128
ADCSRA |= PS_64; // set our own prescaler
}
void loop() {

while(1) {
DrawGrid();
touch();
trigger();

// Collect the analog data into an array

StartSample = micros();
for( int xpos = 0;
xpos < 240; xpos ++) { Sample[ xpos] = analogRead(A0)*5/102;
delayMicroseconds(dTime);
}
EndSample = micros();

// Display the collected analog data from array
for( int xpos = 0; xpos < 239;
xpos ++)
{
// Erase previous display
myGLCD.setColor( 0, 0, 0);
myGLCD.drawLine (xpos + 1, 255-OldSample[ xpos + 1]* vsens-hpos, xpos + 2, 255-OldSample[ xpos + 2]* vsens-hpos);
if (xpos == 0) myGLCD.drawLine (xpos + 1, 1, xpos + 1, 239);
// Draw the new data
myGLCD.setColor (255, 255, 255);
myGLCD.drawLine (xpos, 255-Sample[ xpos]* vsens-hpos, xpos + 1, 255-Sample[ xpos + 1]* vsens-hpos);
}
// Determine sample voltage peak to peak
Max = Sample[ 100];
Min = Sample[ 100];
for( int xpos = 0;
xpos < 240; xpos ++)
{
OldSample[ xpos] = Sample[ xpos];
if (Sample[ xpos] > Max) Max = Sample[ xpos];
if (Sample[ xpos] < Min) Min = Sample[ xpos];
}
// display the sample time, delay time and trigger level
myGLCD.setBackColor( 0, 0, 255);
myGLCD.setFont( SmallFont);
myGLCD.setBackColor( 0, 0, 255);
myGLCD.print("Delay", 260, 5);
myGLCD.print(" ", 270, 20);
myGLCD.print(itoa ( dTime, buf, 10), 270, 20);
myGLCD.print("Trig.", 260, 60);
myGLCD.print(" ", 270, 75);
myGLCD.print(itoa( Trigger, buf, 10), 270, 75);
myGLCD.print("H Pos.", 260, 120);
myGLCD.print( itoa( hpos, buf, 10), 270, 135);
//myGLCD.setBackColor( 0, 0, 0);
SampleTime =( EndSample-StartSample)/1000;
myGLCD.print("Sec.", 205, 210);
myGLCD.print(" ", 280, 30);
myGLCD.print(itoa( SampleTime, buf, 10), 205, 220);
// Range of 0 to 64 * 78 = 4992 mV
SampleSize =( Max-Min)*78;
myGLCD.print("mVolt", 5, 210);
myGLCD.print( itoa( SampleSize, buf, 10),5, 220);
myGLCD.print(itoa( analogRead(A0)*4.15/10.23, buf, 10),110 ,220);

}}

//-------------------------END PROGRAM

Step 7: Video of the Oscope in Action

Step 8: Another Video

Arduino Contest

Runner Up in the
Arduino Contest

Gadget Hacking and Accessories Contest

Second Prize in the
Gadget Hacking and Accessories Contest

4 People Made This Project!

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84 Discussions

0
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johnagDavidPatterson

Reply 4 years ago on Introduction

Sorry for the delay in responding. Thanks for your comment. I don't know the refresh rate of the screen, haven't checked the specs in detail. It would definitely improve the scope if you could increase the bandwidth by using your design. If you get the kit and try your concepts on it , please share.. If I have time I might try it myself..Again thanks.

0
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DavidPattersonjohnag

Reply 4 years ago on Introduction

The 3.2 inch screen and Shield finally arrived. I used my Mega rather than the Sainsmart.

Assembly was easy- I added connecters for the analogue port, pwm10, zero and 5V. Programming was not difficult- Henning, the library author has excellent documentation. I found no issues in implementing his protocols.

My scope runs at up to 237-238 Khz.

The sdcard reader which is on the shield, works and opens up the possibility of data saving. (Not to mention adding pictures)

This has produced a very nice stand alone oscilloscope.

Thanks for your work.

connections.jpgendview.jpginfo.jpgrun.jpgstartup2.jpginsidebox2.jpg

Hi,

For this application I used
Henning's loadBitmap function- which is documented in the examples
supplied with his library. This requires that you convert a screen sized
(or less) picture to raw format. He supplies a program with his library
download for this. Or you can use his online converter at :

http://www.henningkarlsen.com/electronics/t_imagec...

I used a screen sized (320 x 240) file.

#include <tinyFAT.h>
#include <UTFT.h>
#include <UTFT_tinyFAT.h>
#include <UTouch.h>

// Initialize Screen and touch functions
UTFT myGLCD(ITDB32S,38,39,40,41);
UTFT_tinyFAT myFiles(&myGLCD);
UTouch myTouch(6,5,4,3,2);
boolean logo = true;

word res;

const int chipSelect = 53; // sd select pin

void setup(){

pinMode(chipSelect, OUTPUT);

myGLCD.InitLCD();
myGLCD.clrScr();

int picsize_x = myGLCD.getDisplayXSize();
int picsize_y = myGLCD.getDisplayYSize();

if (logo){
if (file.initFAT()==0){
switch (picsize_x);
res = myFiles.loadBitmap(0, 0, picsize_x, picsize_y, "LOGO.RAW");
if (res == 0){
delay(5000);
myGLCD.clrScr();
}

}

}

// more setup stuff

}

The use of the raw file for a one off display is fine.

However
having to convert multiple files seemed a little time consuming to me.
So I wrote an addition to the Henning's utft library to process 24 bit
bmp files directly. This works great and does not require UTFT_tinyFat
and tinyFat. The sdcard can be accessed using the standard arduino sd
library. My patch will load a screen sized bitmap in 1.79S, which is a
little faster than Henning's system.

I have also utilised the sd for data recording.

All in all John has detailed a very useful shield and lcd!

0
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ValtherN

11 months ago

Did anyone per chance design a 3D printable box for this?

0
None
hackerh

1 year ago

Hello

I have a query to make it possible to create Oscilloscope By Arduino UNO and have a fast analogRead can read the signal with high speed for 200KHZ.

If possible, it helps me to accomplish it

Is it possible to give me an example of this is a small program showing the action of ADC fast to take the sample of 200KHZ

This email is www.14laid@gmail.com

Thank

0
None
pipern8536d

1 year ago

Can this unit be installed using the new oled flexible screen?

0
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AMSR1

1 year ago

It seems that the code is working however the Buttons(Delay,Trig etc.) is not working. Is anyone having the same problem?

0
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jwzumwalt

1 year ago

What does "works pretty good for low voltage and low frequencies" mean? Please include some relavent specs in the first one or two paragraphs so we can see if the project is applicable to our needs...

2 replies
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PatrickT90jwzumwalt

Reply 1 year ago

He explains the issue in his other instructable, which is linked in the questioned sentence.

0
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jwzumwaltPatrickT90

Reply 1 year ago

Oh... So this is click bait and not meant to be truly informative?

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lasersystem

1 year ago

Hi,
How I can use Arduino DUE with TFT LCD Sheild with touch.

Thanks so much

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Harry N4HBM

1 year ago

I used the SainSmart boards and it works like a charm.

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Nonametruck

1 year ago

Finally found a nice project, you took some time putting my his on here thanks for taking the time..

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brawls01

1 year ago

How would you modify the code to display a signal between 0.2 and -0.2 volts?