How to make Arduino run a script - arduino

Question

i'm a software developer but i'm new to Arduino, and to the electronics world.
I would like to build a simple project that combined both, and really appreciate any help where to start.
final project should be Arduino with a button and a LED, when tapping the button I want run a script on my mac, then if the script finished successfully i want to turn on the LED
I already saw some tutorial about how to use buttons and LEDs so
the main thing i'm interested here is how communicate from the Arduino to the mac and vice versa. and especially how to make it run a script on my mac.

Answer 1

You should look into the Serial class and the examples (via File > Examples > Commmunication)
You will need to write a bit of code on the Arduino side to send data via Serial when the button is pressed (so you can trigger your script) and receive data (when the script is done) to control the LED.
Here is a rough example on the Arduino side:
const int btnPin = 12;//button pin
const int ledPin = 13;
int lastButtonState;
void setup(){
//setup pins
pinMode(btnPin,INPUT_PULLUP);
pinMode(ledPin,OUTPUT);
//setup communication
Serial.begin(9600);
}
void loop() {
int currentButtonState = digitalRead(btnPin);//read button state
if(lastButtonState != currentButtonState && currentButtonState == LOW){//if the state of the pin changed
Serial.write(currentButtonState);//send the data
lastButtonState = currentButtonState;//update the last button state
//turn on LED
digitalWrite(ledPin,HIGH);
}
}
void serialEvent(){//if any data was sent
if(Serial.available() > 0){//and there's at least 1 byte to look at
int data = Serial.read();//read the data
//do something with it if you want
//turn off the LED
digitalWrite(ledPin,LOW);
}
}
Be aware you may have different pin numbers in your setup and depending on how the button wired, you will either look for a LOW or HIGH value in the in the condition checking the currentButtonState.
In terms of the communication there are a few key elements:
Serial.begin(9600);
Starts Serial communication with baud rate 9600. You will need to match this baud rate on the other end to ensure correct communication.
Serial.write();
Will send data to the port.
serialEvent()
is predefined in Arduino and gets called when new Serial data arrives.
Note that this gets called automatically on a Arduino Uno (and other simpler boards), however this doesn't get called on other boards:
serialEvent() doesn’t work on the Leonardo, Micro, or Yún.
serialEvent() and serialEvent1() don’t work on the Arduino SAMD Boards
serialEvent(), serialEvent1()``serialEvent2(), and serialEvent3() don’t work on the Arduino Due.
On the script side, you haven't mentioned the language, but the principle is the same: you need to know the port name and baud rate to establish communication from your mac.
(You can manually call serialEvent() in loop() as a workaround. For more details see the Arduino Reference)
The port is what you used to upload the Arduino code (something like /dev/tty.usbmodem####) and in this particular case the baud rate is 9600. You should be able to test using Serial Monitor in the Arduino IDE.
Your script will be something along there lines (pseudo code)
open serial connection ( port name, baudrate = 9600 )
poll serial connection
if there is data
run the script you need
script finished executing, therefore send data back via serial connection
Be sure to checkout the Interfacing with Software to find guide on the scripting language of your choice
Update
Here's a quick example using Processing to interface with the arduino using it's Serial library. So on the Arduino side, here's a minimal sketch:
const int btnPin = 12;//button pin
const int ledPin = 13;
boolean wasPressed;
char cmd[] = "/Applications/TextEdit.app\n";
void setup(){
//setup pins
pinMode(btnPin,INPUT_PULLUP);
pinMode(ledPin,OUTPUT);
//setup communication
Serial.begin(9600);
}
void loop() {
int currentButtonState = digitalRead(btnPin);//read button state
if(!wasPressed && currentButtonState == LOW){//if the state of the pin changed
Serial.write(cmd);//send the data
wasPressed = true;//update the last button state
//turn on LED
digitalWrite(ledPin,HIGH);
}
if(currentButtonState == HIGH) wasPressed = false;
}
void serialEvent(){//if any data was sent
if(Serial.available() > 0){//and there's at least 1 byte to look at
int data = Serial.read();//read the data
//do something with it if you want
//turn off the LED
digitalWrite(ledPin,LOW);
}
}
and on the Processing side:
import processing.serial.*;
void setup(){
try{
Serial arduino = new Serial(this,"/dev/tty.usbmodemfa141",9600);
arduino.bufferUntil('\n');//buffer until a new line is encountered
}catch(Exception e){
System.err.println("Error opening serial connection! (check cables and port/baud settings!");
e.printStackTrace();
}
}
void draw(){}
void serialEvent(Serial s){
String[] command = s.readString().trim().split(",");//trim spaces, split to String[] for args
println(command);//see what we got
open(command);//run the command
s.write("A");//send a message back to flag that the command is finished (turn LED off)
}
Hope this is a helpful proof of concept. Feel free to use any other language with a serial library available instead of Processing. The syntax may differ just a tad (probably more on the running of the process/command), but the concept is the same.
Update The example above can be simplified a touch by not having the command on the Arduino side:
there's less data sent on Serial from Arduino to Processing reducing communication time and the odds of communication interference
the app runs on a computer hence changing the command is simpler to do on software side as opposed to having to change the Arduino code and re-upload each time.
Arduino:
const int btnPin = 12;//button pin
const int ledPin = 13;
boolean wasPressed;
void setup(){
//setup pins
pinMode(btnPin,INPUT_PULLUP);
pinMode(ledPin,OUTPUT);
//setup communication
Serial.begin(9600);
}
void loop() {
int currentButtonState = digitalRead(btnPin);//read button state
if(!wasPressed && currentButtonState == LOW){//if the state of the pin changed
Serial.write('R');//send the data
wasPressed = true;//update the last button state
//turn on LED
digitalWrite(ledPin,HIGH);
}
if(currentButtonState == HIGH) wasPressed = false;
}
void serialEvent(){//if any data was sent
if(Serial.available() > 0){//and there's at least 1 byte to look at
int data = Serial.read();//read the data
//do something with it if you want
//turn off the LED
digitalWrite(ledPin,LOW);
}
}
Processing:
import processing.serial.*;
String[] command = {"/Applications/TextEdit.app", "myText.txt"};
void setup() {
try {
Serial arduino = new Serial(this, "/dev/tty.usbmodemfa141", 9600);
}
catch(Exception e) {
System.err.println("Error opening serial connection! (check cables and port/baud settings!");
e.printStackTrace();
}
}
void draw() {
}
void serialEvent(Serial s) {
if (s.read() == 'R') {
launch(command);//run the command
s.write("A");//send a message back to flag that the command is finished (turn LED off)
}
}
(btw, 'R' is an arbitrary single character, can be something else as long it's the same char on both Serial send and receive sides)
Also, bare in mind launch() returns Proccess which can be useful to get more information from the software launched.

Answer 2

Dunno if it will help you as much as it did me but this question shows a simple example of how to use the script with a simple button in an android app
Run script with android app
Hope it helps

Answer 3

I found a workaround in Linux. It's a little messy but it works. I use Coolterm to capture the serial output from the arduino to a text file and I wrote a small python script that reads the file (or simply, in my case, executes the command I want if the file is not empty).