Last Recitation Interlab Kris

The last recitation reviews the use of map function, and I went to Prof. Moon’s workshop to review Serial Communication. Prof. Moon didn’t leave us a homework, instead,　he asks us to review what he taught in class and finish the implementation.

We reviewed the use of serial communication code in class:

Arduino to processing is what we will use in final, so we focus more on it in this blog:


void setup() {
Serial.begin(9600);
}

void loop() {
int sensor1 = analogRead(A0);
int sensor2 = analogRead(A1);
int sensor3 = analogRead(A2);

// keep this format
Serial.print(sensor1);
Serial.print(","); // put comma between sensor values
Serial.print(sensor2);
Serial.print(",");
Serial.print(sensor3);
Serial.println(); // add linefeed after sending the last sensor value

// too fast communication might cause some latency in Processing
// this delay resolves the issue.
delay(100);
}



import processing.serial.*;

String myString = null;
Serial myPort;

int NUM_OF_VALUES = 3; /** YOU MUST CHANGE THIS ACCORDING TO YOUR PROJECT **/
int[] sensorValues; /** this array stores values from Arduino **/

void setup() {
size(500, 500);
background(0);
setupSerial();
}

void draw() {
updateSerial();
printArray(sensorValues);

// use the values like this!
// sensorValues[0]

// add your code

//
}

void setupSerial() {
printArray(Serial.list());
myPort = new Serial(this, Serial.list()[ PORT_INDEX ], 9600);
// WARNING!
// You will definitely get an error here.
// Change the PORT_INDEX to 0 and try running it again.
// And then, check the list of the ports,
// find the port "/dev/cu.usbmodem----" or "/dev/tty.usbmodem----"
// and replace PORT_INDEX above with the index number of the port.

myPort.clear();
// Throw out the first reading,
// in case we started reading in the middle of a string from the sender.
myString = myPort.readStringUntil( 10 ); // 10 = '\n' Linefeed in ASCII
myString = null;

sensorValues = new int[NUM_OF_VALUES];
}

void updateSerial() {
while (myPort.available() > 0) {
myString = myPort.readStringUntil( 10 ); // 10 = '\n' Linefeed in ASCII
if (myString != null) {
String[] serialInArray = split(trim(myString), ",");
if (serialInArray.length == NUM_OF_VALUES) {
for (int i=0; i<serialInArray.length; i++) {
sensorValues[i] = int(serialInArray[i]);
}
}
}
}
}


We understand several important use of it:

1. the change of port numbers
2. the use of comma and println / print
3. different between write and print that is: output bytes / string
4. number of sensor values

map function is to map a value based on a certain range: map(value, r00, r01, r10, r11)
which is handy and the theory behind is also very simple:

it is a linear transformation f(x) = kx + b , where k, b can be calculated by the 4 r’s