REST API for IoT device in Raspberry Pi

Introduction

A REST API lets your IoT device talk to other devices or apps over the internet easily. It helps you control or get data from your device remotely.

You want to check sensor data from your Raspberry Pi using a phone app.

You want to turn on/off a light connected to your Raspberry Pi from anywhere.

You want to collect temperature readings from multiple devices in one place.

You want to update device settings without physically touching the device.

You want to build a web dashboard to monitor your IoT devices.

Syntax

Raspberry Pi

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/status', methods=['GET'])
def get_status():
    return jsonify({'status': 'Device is running'})

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

Use Flask, a simple Python web framework, to create REST APIs on Raspberry Pi.

Define routes with @app.route to handle different API endpoints.

Examples

This example returns a fixed temperature value as JSON when you visit /temperature.

Raspberry Pi

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/temperature', methods=['GET'])
def temperature():
    temp = 25  # example sensor value
    return jsonify({'temperature': temp})

This example accepts a POST request to turn an LED on or off by sending JSON with a 'state' key.

Raspberry Pi

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/led', methods=['POST'])
def control_led():
    data = request.json
    state = data.get('state')
    # Here you would add code to turn LED on/off
    return jsonify({'led_state': state})

Sample Program

This program creates two API endpoints: one to get sensor data and one to control an LED. It runs on the Raspberry Pi and listens on all network interfaces.

Raspberry Pi

from flask import Flask, jsonify, request

app = Flask(__name__)

# Simulated sensor data
sensor_data = {'temperature': 22, 'humidity': 60}

@app.route('/sensor', methods=['GET'])
def get_sensor_data():
    return jsonify(sensor_data)

@app.route('/led', methods=['POST'])
def set_led():
    data = request.json
    state = data.get('state')
    if state not in ['on', 'off']:
        return jsonify({'error': 'Invalid state'}), 400
    # Simulate setting LED state
    return jsonify({'led_state': state})

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

Important Notes

Make sure your Raspberry Pi and client device are on the same network or properly configured for internet access.

Use tools like Postman or curl to test your REST API endpoints.

For real devices, replace simulated data with actual sensor readings and hardware control code.

Summary

A REST API helps your IoT device communicate over the network easily.

Flask is a simple way to create REST APIs on Raspberry Pi using Python.

You can get sensor data or control hardware remotely using API endpoints.

Practice

1. What is the main purpose of a REST API on a Raspberry Pi IoT device?

easy

A. To connect the Raspberry Pi to a monitor

B. To allow remote communication and control over the network

C. To store large amounts of data locally

D. To increase the Raspberry Pi's processing speed

Solution

1. Step 1: Understand REST API role

   A REST API enables devices to communicate over a network using standard web protocols.

2. Step 2: Identify IoT device needs

   IoT devices use REST APIs to send sensor data or receive commands remotely.

3. Final Answer:

   To allow remote communication and control over the network -> Option B

4. Quick Check:

   REST API = Remote communication [OK]

Hint: REST APIs enable network communication for IoT devices [OK]

Common Mistakes:

• Confusing REST API with hardware speed
• Thinking REST API stores data locally
• Assuming REST API connects to display devices

2. Which Python library is commonly used on Raspberry Pi to create a REST API for IoT devices?

easy

A. Flask

B. NumPy

C. Pandas

D. Matplotlib

Solution

1. Step 1: Identify common Python libraries

   NumPy, Pandas, and Matplotlib are for data processing and visualization, not REST APIs.

2. Step 2: Recognize Flask's role

   Flask is a lightweight web framework used to build REST APIs easily on Raspberry Pi.

3. Final Answer:

   Flask -> Option A

4. Quick Check:

   Flask = REST API framework [OK]

Hint: Flask is the go-to Python web framework for REST APIs [OK]

Common Mistakes:

• Choosing data libraries instead of web frameworks
• Confusing Flask with data analysis tools
• Assuming Matplotlib creates APIs

3. What will be the output of this Flask route code on a Raspberry Pi?

from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/sensor')
def sensor():
    data = {'temperature': 22, 'humidity': 60}
    return jsonify(data)

# Assume app is running and /sensor is requested

medium

A. {"temperature": 22, "humidity": 60}

B. temperature=22, humidity=60

C. temperature: 22, humidity: 60

D. Error: jsonify not defined

Solution

1. Step 1: Understand jsonify function

   jsonify converts Python dict to JSON string with correct headers for API response.

2. Step 2: Analyze route output

   The route returns JSON with keys 'temperature' and 'humidity' and their values.

3. Final Answer:

   {"temperature": 22, "humidity": 60} -> Option A

4. Quick Check:

   jsonify(dict) = JSON string [OK]

Hint: jsonify returns JSON string from dict in Flask [OK]

Common Mistakes:

• Expecting plain text instead of JSON
• Confusing jsonify with HTML output
• Missing import of jsonify causing errors

4. Identify the error in this Flask route code for Raspberry Pi IoT device:

from flask import Flask
app = Flask(__name__)

@app.route('/led/on')
def led_on():
    GPIO.output(17, True)
    return 'LED is ON'

medium

A. Return statement must be JSON, not string

B. Route decorator syntax is incorrect

C. Missing import and setup for GPIO module

D. Flask app is not created properly

Solution

1. Step 1: Check GPIO usage

   GPIO module must be imported and configured before use to control pins.

2. Step 2: Verify code completeness

   Code lacks 'import RPi.GPIO as GPIO' and GPIO setup like GPIO.setmode() and GPIO.setup().

3. Final Answer:

   Missing import and setup for GPIO module -> Option C

4. Quick Check:

   GPIO needs import and setup before use [OK]

Hint: Always import and setup GPIO before controlling pins [OK]

Common Mistakes:

• Assuming Flask route syntax is wrong
• Thinking return must be JSON always
• Ignoring GPIO initialization steps

5. You want to create a REST API on Raspberry Pi that returns sensor data only if temperature is above 25°C. Which code snippet correctly implements this logic using Flask?

hard

A. from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/sensor')
def sensor():
temp = 30
if temp >= 25:
return {'temperature': temp}
else:
return {'message': 'Temperature too low'}

B. from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/sensor')
def sensor():
temp = 20
if temp < 25:
return jsonify({'temperature': temp})
else:
return jsonify({'message': 'Temperature too low'})

C. from flask import Flask
app = Flask(__name__)

@app.route('/sensor')
def sensor():
temp = 30
if temp > 25:
return {'temperature': temp}
else:
return {'message': 'Temperature too low'}

D. from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/sensor')
def sensor():
temp = 30
if temp > 25:
return jsonify({'temperature': temp})
else:
return jsonify({'message': 'Temperature too low'})

Solution

1. Step 1: Check temperature condition logic

   We want to return data only if temperature is above 25, so 'temp > 25' is correct.

2. Step 2: Verify response format

   Flask needs jsonify to return proper JSON response with correct headers.

3. Final Answer:

   Code with temp=30, condition temp > 25, and jsonify responses -> Option D

4. Quick Check:

   Use temp > 25 and jsonify for JSON response [OK]

Hint: Use if temp > 25 and jsonify() to return JSON [OK]

Common Mistakes:

• Using wrong temperature comparison operator
• Returning dict without jsonify causing errors
• Setting temperature below threshold incorrectly