Arduino based Oscilliscope

const int analogInPin1 = A0;
static unsigned char adcval;

void setup()
{
Serial.begin(115200);

pinMode(13, OUTPUT);

ADCSRA = 0; // clear ADCSRA register
ADCSRB = 0; // clear ADCSRB register
ADMUX |= (0 & 0x07); // set A0 analog input pin
ADMUX |= (1 << REFS0); // set reference voltage
ADMUX |= (1 << ADLAR); // left align ADC value to 8 bits from ADCH register

// sampling rate is [ADC clock] / [prescaler] / [conversion clock cycles]
// for Arduino Uno ADC clock is 16 MHz and a conversion takes 13 clock cycles
//ADCSRA |= (1 << ADPS2) | (1 << ADPS0); // 32 prescaler for 38.5 KHz
ADCSRA |= (1 << ADPS2); // 16 prescaler for 76.9 KHz
//ADCSRA |= (1 << ADPS1) | (1 << ADPS0); // 8 prescaler for 153.8 KHz

ADCSRA |= (1 << ADATE); // enable auto trigger
ADCSRA |= (1 << ADIE); // enable interrupts when measurement complete
ADCSRA |= (1 << ADEN); // enable ADC
ADCSRA |= (1 << ADSC); // start ADC measurements
}

ISR(ADC_vect)
{
adcval = ADCH; // read 8 bit value from ADC
}

void loop()
{
Serial.write(adcval);

// Following code to generate ref signal at pin 13 @ 50HZ. You can connect A0 to see the waveform in PCScope.exe
ctr++;
if(ctr>117) //117=10.03ms
{
ctr=0;
flag_tog = !flag_tog;
digitalWrite(13, flag_tog);
}

}

this is the code of aurdino based osciloscope
but problem is that it gives only positive cycle instead of showing both positive and negative cycles.
help me please if any solution available??

usamasaif49:
this is the code of aurdino based osciloscope
but problem is that it gives only positive cycle instead of showing both positive and negative cycles.
help me please if any solution available??

What has this do you with this one year old thread. If you have a problem start your own thread but only after you read the how to use this forum sticky post to find out how to post code correctly.

@usamasaif49 Your post has been split off to its own topic

Please do not hijack old topics

Please follow the advice given in the link below when posting code . Use code tags when posting code here to make it easier to read and copy for examination

Hello
Did you study how does an analog-input of an Arduino operates?