An int in this context is 16 bit (two bytes). Arduino’s ADC is 10-bit, indeed. So, any result of analogRead will obviously have the upper 6 bits as zeros. The code above wants to write the data to serial output. Serial.write can write bytes, strings or arrays (must specify the length). The author of the above code decide to write it as bytes. A 16-bit int consists of two bytes (in our case the upper byte has only 2 relevant digits, the rest are zeros, but it doesn’t really matter). To extract the upper and lower bytes from an int, we can use respectively (val >> 8) & 0xff and val & 0xff. This is basic binary arithmetic. Just write 16 random binary digits on a piece of paper and do these operations by hand: “shift right by 8 positions, with the overflowing digits just disappearing, then bitwise AND 111111111”, or just “bitwise AND 11111111” and you will see how it works.
You mentioned val & 0x00 (might as well have written val & 0), this doesn’t make sense, this will be always zero (anything & 0 is 0). If something’s still not clear, just read up on bitwise binary arithmetic operators

sorry but 16 bit is around 65k resolution. So 1024 is 10 bit resolution and 8 bit is only 256 but dont understant why the corect way is not “Serial.write( val & 0x00 );”?? i get that left shift 8 positions and then write “val” witch is 10 positions but after that 0xff is 256 or 8 bit .. and last 2 bits are they not somehow colide with your 10 bit val… i know i missing something 🙂

I know this was asked a long time ago, but in case someone is reading this and wondering, the code reads read the value (voltage) from pin ANALOG_IN (defined earlier as pin 0) into variable “val” of type integer (which is 16-bit). This value is from 0 to 1023 (corresponding to the range of 0 V to VCC V – 5V or 3.3V depending on which Arduino board is it). It then sends this value to the serial port (-> USB port of the computer), with a “magic” prefix of 0xFF. (val >> 8) & 0xff is the upper 8 bits of the 16-bit int, and val & 0xff is the lower 8 bits – >> and & are just binary operations (right shift and binary AND).

OK – room for the serial plotter to improve, I guess.

You still didn’t answer my first question 🙂

What is this code doing:
int val = analogRead(ANALOG_IN);
Serial.write( 0xff );
Serial.write( (val >> 8) & 0xff );
Serial.write( val & 0xff );

Thanks!

More information on the serial plotter: http://randomnerdtutorials.com/arduino-serial-plotter-new-tool/
Yes, but the serial plotter is very limited and it doesn’t offer most of the features that processing does

Can you explain what the code is doing?
Can the o’scope traces be displayed in the serial plotter? How would you do that?

Thanks!

You can only upload one program to an Arduino