arduino-serial-fetch

This app converts serial messages from an Arduino to REST API requests. It has been developed to correspond specifically with the REST API service provided by arduino-api-server and is structured solely to update pin data.

• Requirements
• Getting Started
• Arduino code and Serial.print() format
• Adding more pins
• Test API endpoints

Requirements

• arduino-api-server
• Arduino serial messages must following a specific format. See Arduino code and Serial.print() format
• Arduino must be tethered to your computer

Getting Started

1. First complete your arduino-api-server setup

2. Download/clone this repo or use it as a template

3. Connect your Arduino to your computer and upload the corresponding Arduino program to it. See Arduino code and Serial.print() format.

4. Create your env file.

   cp .env.dist .env

5. Update the .env file with values that match your configuration:

   var	default	description
   API_HOST	http://localhost:3000	The host URL of your API server (see arduino-api-server). Note: if you are deploying with localtunnel, you should continue to use localhost:3000 as your API_HOST
   SERIALPORT	/dev/tty.SLAB_USBtoUART	The serial port your Arduino is connected to. Should match the port name you use in the Arduino IDE.
   BAUDRATE	9600	Match the baudrate used in your Arduino code. Check Serial.begin(9600); in your Arduino setup()
   INTERVAL	500	Frequency of API requests (in milliseconds)

6. Install dependencies

   npm install

7. Run the app

   npm start

   To stop the app, use ctrl-c (^C)

Arduino code and Serial.print() format

This app assumes that your Arduino code is only printing one line to the Serial port per loop() iteration and is constructed like so:

// for three pins
<number>\t<number>\t<number>\t\n

Each number represents pin data, with \t as the delimiter. \n signifies the end of the data reading for one iteration in loop(). It is up to the interpreter to know the order of the pins and how that should correspond to their usage (see Adding more pins).

You can use /arduinoSerial/arduinoSerial.ino as boilerplate for your Arduino code with pins modified as needed.

Adding more pins

The app defaults to reading and sending the following pins:

• A0
• A1
• D2

This can be modified by updating both the:

1. Arduino code: read the necessary pins and append to the Serial.print message
2. main.js: modify the constructed allPins array that is used to generate API requests.

For example, say I needed to read pins A0, A3, D4, and D7. I would need to modify my code like so:

// arduinoSerial.ino

int knobPin = A0;
int knobValue = 0;

int sensorPin = A3;
int sensorValue = 0;

int button1Pin = D4;
int button1Value = 0;

int button2Pin = D7;
int button2Value = 0;

void setup() {
  pinMode(button1Pin, INPUT);
  pinMode(button2Pin, INPUT);
  Serial.begin(9600);
}

void loop() {
  // A0 will be pins[0]
  knobValue = analogRead(knobPin);
  Serial.print(knobValue);
  Serial.print("\t");

  // A3 will be pins[1]
  sensorValue = analogRead(sensorPin);
  Serial.print(sensorValue);
  Serial.print("\t");

  // D4 will be pins[2]
  buttonValue = digitalRead(button1Pin);
  Serial.print(button1Value);
  Serial.print("\t");

  // D7 will be pins[3]
  buttonValue = digitalRead(button2Pin);
  Serial.print(button2Value);
  Serial.print("\t");

  Serial.println();

}

// main.js excerpt
const allPins = [
  {
    id: "A0",
    value: pins[0],
  },
  {
    id: "A3",
    value: pins[1],
  },
  {
    id: "D4",
    value: pins[2],
  },
  {
    id: "D7",
    value: pins[3],
  },
];

Note how the pins[] array index does not necessarily correspond to the Arduino pin number.

Test API endpoints

If you don't have an Arduino connected, you can mimic one with the test.js script. This is useful if you just want to test your endpoints. The test script will also send API requests at the same INTERVAL defined in your .env file.

npm test

To stop the test, use ctrl-c (^C)