Serving sensor data as JSON API in Raspberry Pi - Step-by-Step Execution

Concept Flow - Serving sensor data as JSON API

Start Raspberry Pi

↓

Initialize Sensor

↓

Read Sensor Data

↓

Format Data as JSON

↓

Start Web Server

↓

Wait for API Request

↓

Send JSON Response

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Repeat Reading & Serving

The Raspberry Pi reads sensor data, formats it as JSON, and serves it via a web API on request.

Execution Sample

Raspberry Pi

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

@app.route('/sensor')
def sensor():
    data = {'temperature': 22.5, 'humidity': 60}
    return jsonify(data)

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

This code creates a simple web API that returns sensor data as JSON when '/sensor' is requested.

Execution Table

Step	Action	Sensor Data Read	JSON Data	API Response Sent
1	Start Raspberry Pi and initialize sensor	None	None	No
2	Read sensor data	{temperature: 22.5, humidity: 60}	None	No
3	Format data as JSON	{temperature: 22.5, humidity: 60}	{"temperature": 22.5, "humidity": 60}	No
4	Wait for API request at '/sensor'	{temperature: 22.5, humidity: 60}	{"temperature": 22.5, "humidity": 60}	No
5	Receive API request	{temperature: 22.5, humidity: 60}	{"temperature": 22.5, "humidity": 60}	No
6	Send JSON response	{temperature: 22.5, humidity: 60}	{"temperature": 22.5, "humidity": 60}	Yes
7	Repeat reading and serving on next request	Next sensor read	Next JSON data	No

💡 Server runs continuously, serving JSON data on each API request.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 6	Final
sensor_data	None	{temperature: 22.5, humidity: 60}	{temperature: 22.5, humidity: 60}	{temperature: 22.5, humidity: 60}	Updated on each read
json_data	None	None	{"temperature": 22.5, "humidity": 60}	{"temperature": 22.5, "humidity": 60}	Updated on each read

Key Moments - 3 Insights

Why do we format sensor data as JSON before sending?

JSON is a standard format that web clients understand easily. The execution_table row 3 shows data being converted to JSON before sending.

Does the server read sensor data on every API request?

Yes, the server reads fresh sensor data before sending a response, as shown in execution_table rows 2 and 7.

What happens if no API request is made?

The server waits idle, as shown in execution_table row 4, until it receives a request to respond.

Visual Quiz - 3 Questions

Look at the execution_table, what is the JSON data at Step 3?

A {"temperature": 22.5, "humidity": 60}

B {temperature: 22.5, humidity: 60}

C None

D Empty string

💡 Hint

Check the JSON Data column at Step 3 in the execution_table.

At which step does the API response get sent?

A Step 4

B Step 6

C Step 5

D Step 7

💡 Hint

Look at the API Response Sent column in the execution_table.

If sensor data changes, which variable in variable_tracker updates?

A json_data only

B sensor_data only

C Both sensor_data and json_data

D Neither variable

💡 Hint

See variable_tracker rows for sensor_data and json_data changes.

Concept Snapshot

Serving sensor data as JSON API:
- Initialize sensor and web server
- Read sensor data
- Convert data to JSON format
- Wait for API request
- Send JSON response
- Repeat for each request

Full Transcript

This example shows how a Raspberry Pi reads sensor data and serves it as a JSON API. First, the sensor is initialized. Then the Pi reads data like temperature and humidity. This data is converted into JSON format, which is a simple text format that computers and web browsers understand. A web server runs on the Pi, waiting for requests. When a request comes to the '/sensor' URL, the server sends the JSON data as a response. This process repeats for every new request, always sending fresh sensor data.