Serial Communication

Forum 2005-2010 (read only) Software Syntax & Programs
1

I am having trouble with serial communication. I want to send data from my Arduino to a touch screen. The data that I am sending will be obtained from the analogRead function.

My question is, analogRead is a 10bit number. If I do
Serial.write(analogRead(5));
and lets just assume that the value of analogRead(5) is 200...will it send 11001000, which is only 8 bits or will it send 0011001000, which is 10 bits?

Also if i say:

int val = analogRead(5);
Serial.write(val);

will it send 16 bits or will it only send the amount of bits necessary to describe the value?

I am asking about this because I will be sending a bunch of values from the arduino to the touch screen using analogRead and serial.write and if I know the arduino will send 10 bits for each sensor regardless of the value of the number then it will be easy to determine which bits belong to which sensor in the stream of data being sent.

If this is not the case the I guess I will have to send some kind of marker at the end of each sensor to separate them.

Thanks!

2

and lets just assume that the value of analogRead(5) is 200...will it send 11001000, which is only 8 bits or will it send 0011001000, which is 10 bits

The return type of "analogRead" is "int", so that's what "Serial.print" will write - sixteen signed bits, expressed as an ASCII integer.

3

Serial.print() will convert the integer to a string (an array of characters) and send the characters (8 bits each) to the serial port.

Serial.write() does not have an overloaded method to write ints, only bytes. So, you need to break the int into two bytes, and send the MSB then the LSB, each of which will result in sending 8 bits.