How to write 10-bit ADC values to the 8-bit serial with Arduino?

The following code:

int sensorValue = analogRead(A0);
Serial.println(sensorValue, DEC);

Outputs (text):

0
1023

for the same input values the following code:

int sensorValue = analogRead(A0);
Serial.write(sensorValue);

Outputs (bytes)

00 63

The 0 got through, but the 1023 resulted in 63. This happens because:

1. ADC resolution is 10-bit
2. Thus the maximum value is 1023 (0x3FF)
3. Serial.Write writes the more valuable 8 bits
4. Serial.Write considers the ADC output as a 12 bit variable
5. 63 (0x3F) are the 8 more valuable bits in this variable

So what you have to do is to fix this behavior

int upperByte = (sensorValue & 0x300) >> 8;
int lowerByte = sensorValue & 0xFF;
Serial.write(lowerByte);
Serial.write(upperByte);

Then you will get right aligned data:

00 00 FF 03

With

int upperByte = (sensorValue & 0x3FC) >> 2;
int lowerByte = (sensorValue & 0x3) << 6;

You get left aligned data for unsigned integers

00 00 C0 FF

With

int upperByte = (sensorValue & 0x3F8) >> 3;
int lowerByte = (sensorValue & 0x7) << 5;

You get left aligned data for signed integers

00 00 E0 7F