Serial Call and Response with ASCII-encoded output using Arduino

This example demonstrates string-based communication from the Arduino board to the computer using a call-and-response (handshaking) method.

The sketch sends an ASCII string on startup and repeats that until it gets a serial response from the computer. Then it sends three sensor values as ASCII-encoded numbers, separated by commas and terminated by a linefeed and carriage return, and waits for another response from the computer.

You can use the Arduino serial monitor to view the sent data, or it can be read by Processing (see code below), Flash, PD, Max/MSP (see example below), etc. The examples below split the incoming string on the commas and convert the string into numbers again.

Compare this to the Serial call and response example. They are similar, in that both use a handshaking method, but this one encodes the sensor readings as strings, while the other sends them as binary values. While sending as ASCII-encoded strings takes more bytes, it means you can easily send values larger than 255 for each sensor reading. It’s also easier to read in a serial terminal program.

Software Required

• Processing or
• Max/MSP version 5

Circuit

Connect analog sensors to analog input pin 0 and 1 with 10Kohm resistors used as voltage dividers. Connect a pushbutton or switch connected to digital I/O pin 2 with a 10Kohm resistor as a reference to ground.

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Schematic

Code

int firstSensor = 0; // first analog sensor
int secondSensor = 0; // second analog sensor
int thirdSensor = 0; // digital sensor
int inByte = 0; // incoming serial byte

void setup() {
// start serial port at 9600 bps and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}

pinMode(2, INPUT); // digital sensor is on digital pin 2
establishContact(); // send a byte to establish contact until receiver responds
}

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