Using Asterisk PBX to Control an Arduino

Using Asterisk PBX to Control an Arduino

Dan Wagoner
Dan Wagoner

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If you’ve ever wondered how to bridge the world of telephony (via Asterisk) with the physical world of microcontrollers (via Arduino), this project is for you. I built a mini system where a call to Asterisk triggers an LED on the Arduino.

In many “Internet of Things” setups, microcontrollers handle sensors and actuators. Telephony systems like Asterisk are often kept separate. But I wanted to merge the two: letting a phone call trigger a physical piece of hardware.

Code repo: https://github.com/danwagoner/arduino-asteriskcontrol

High-Level Overview

  • A call (or an IVR option) in Asterisk triggers an AGI script.
  • The AGI script communicates over TCP to the Arduino with an Ethernet shield.
  • The Arduino receives a command and turns an LED on, off or blink.

So effectively: call → AGI script → TCP message to Arduino.

How It Works: Step by Step

Here’s the flow of operations from a call to LED action.

1. Asterisk Call/AGI

You configure Asterisk to call arduino_asteriskcontrol.php via AGI. This script runs when the call reaches a certain extension or context.

2. The PHP Script Connects to Arduino

Within arduino_asteriskcontrol.php:

  • It opens a TCP connection to the Arduino’s IP and port.
  • The user is voice-prompted to choose LED mode (0 = off, 1 = on, 2 = blink).
  • It then sends the corresponding ASCII char to the Arduino over the socket.

3. Arduino Sketch Receives Commands

In arduino_asteriskcontrol.pde:

  • The Arduino sets up an Ethernet server listening (port 23 in the code) via a WIZnet Ethernet shield.
  • It listens for a connection (server.available()) and then reads a byte x = client.read();.
  • Based on the byte value:
    • 0 → LED pin LOW (off)
    • 1 → LED pin HIGH (on)
    • 2 → blinking: HIGH, delay, LOW, delay in loop. :contentReference[oaicite:9]{index=9}

4. Result: Hardware Action

When the Arduino receives the command it executes the appropriate LED state change.

Hardware & Network Requirements

  • An Arduino board (e.g., Uno or similar)
  • Ethernet shield (WIZnet-based, configured with MAC + static IP in sketch)
  • LED (pin defined in sketch as LEDpin = 4) and appropriate resistor.
  • A network connection between the Arduino and the Asterisk server so that the TCP socket can be opened.
  • Asterisk server configured to run the PHP AGI script and permitted to reach the Arduino.

Get Started

  1. Clone the repo: git clone https://github.com/danwagoner/arduino-asteriskcontrol.git
  2. Set up hardware: Install Arduino plus Ethernet shield, assign it IP 192.168.15.15 in the sketch.
  3. Wire the LED: LED to pin 4, set up pinMode(LEDpin, OUTPUT) in setup().
  4. Flash the sketch to the Arduino.
  5. Set up Asterisk: In extensions.conf, add a context where calls hit the AGI script arduino_asteriskcontrol.php.
  6. Edit arduino_asteriskcontrol.php: Update $arduino_ip, $arduino_port, prompts, and TTS engine settings to match my system.
  7. Test call: Place a call, navigate the prompt, and watch the LED light up or blink.
  8. Debug: Check the Arduino serial output and network connectivity if things didn’t trigger. The sketch includes Serial.begin(9600) for troubleshooting.
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