Make a digital oscilloscope via Arduino

Description

Originally written by suyanping

Often seen people making online digital oscilloscope, DSO must have digital-analog conversion unit, according to d/a conversion circuit can be divided into two modes: 1. Special ADC chip + single-chip, 2. using single-chip ADC count inside the converter. For the first model I tried two (see my blog: http://blog.Sina.com.CN/ntwhq), this circuit is a little more complex, component is more difficult to complete, it is difficult for beginners. The second structure is relatively simple, easyto make, but has a significant drawback, that is, withina narrow bandwidth, one of the more typical works are the overseas friends of http://www.serasidis.gr/circuits/AVR_oscilloscope/avr_oscilloscope.htm, the bandwidth of the oscilloscope only 7.7KHz. Domestic users and STC single-chip AVR production, but the

Details

Recently saw a net friend with Arduino oscilloscope, itmay be easier than the second method above, but their results are not ideal, the bandwidth is narrow. So I wanted to try and see and there is no good way to solve this problem. Produced by experiment, and constantly modify the code, and improved d/a conversion sample rate, very good results have been achieved.

The main parameters of the final product:

Frequency response: 10Hz-50KHz

Power supply: 5V

LCD LCD screen: 128x64 (ST7920)

Measurement display area: 96x64

Information display: 32x64, displays the frequency of the test signal, Vpp, and more

Sync: rising edge triggers

Scan speed: 0.02ms/div~10ms/div, carrying nine 1-2-5

Hold function: freeze the displayed waveform and parameters

Second, basic test

Using the Arduino project's biggest advantage is its rich resources, and do not need much knowledge of SCM. I made using a repository u8glib LCD, making it easier to program, or LCD drive will cost you a lot of time.

Use Fusion PCB service to make the PCB if you like.

U8glib download: u8glib_arduino_v1.13.zip (989.55 KB, downloads: 2577)

Here is my first test circuit for Arduino UNO building, of 12864 LCD LCD using ST7920 control.

As long as the input method in the following code, compiled after download you can achieve the basic functions of digital oscilloscope, wouldn't it be simpler?

# Include <U8glib.h>//statement

U8GLIB_ST7920_128X64_4X u8g(13, 12, 11); Statement LCD SPI Com:SCK =13, MOSI = 12, CS = 11

int x,y; Painted point coordinates

int Buffer[128]; Cache storage array

void setup( ) { }

Sample

void sample( )

{

for(x = 0;x < 128;x++)

Buffer[x] = analogRead(A0); Signal sampling

for(x = 0;x < 128;x++)

Buffer[x] = 63-(Buffer[x]>>4); Calculate y values

}

Display

void draw( )

{

for(x = 0;x < 127;x++)

u8g.drawLine(x,Buffer[x],x,Buffer[x+1]); Draw two lines

u8g.drawLine(64,0,64,63); Draw the axes

u8g.drawLine(0,32,128,32);

For (x=0;x<128;x+=8)//draw the axis scale

u8g.drawLine(x,31,x,33);

for(x=0;x<64;x+=8)

u8g.drawLine(63,x,65,x);

u8g.drawFrame(0,0,128,64); Draw border

}

void loop( )

{

sample(); Sample

u8g.firstPage(); Clear screen

do draw( ); Display

while( u8g.nextPage( ));

}

circuit

Using the test circuit, my Arduino is measured directlyusing the analogRead () function to complete a d/a conversion for about 111 μs conversion speed is slow, so much of its bandwidth is 1KHz, the next priority is to improve the speed of digital-analog conversion, while adding other features.

Third, the latest programs

Here is the latest source code using, please keep my boot LOGO, HA HA.

Arduino_oscilloscope.zip (2.72 KB, downloads: 2710)

Program chip 1.1V ADC use voltage reference mentioned above, if you want to use external 5V reference voltage should be program

ADMUX=0xe0; To: ADMUX=0x60;

Vpp= (V_max-V_min) *1.1/255; read: Vpp= (V_max-V_min) *5/255;

Four, machine made

Experiments using the Arduino UNO above, the actualcard when using the Arduino PRO mini, so as to have a smaller volume.

Circuit diagram: