ESP-IDF Basics - Assign. 2.3 (Optional)

Table of Contents

Add a new route to the HTTP server for a programmable blink (Optional)

WS00A - This article is part of a series.

Part 1: ESP-IDF Basics - Lecture 1

Part 2: ESP-IDF Basics - Assign. 1.1

Part 3: ESP-IDF Basics - Assign. 1.2

Part 4: ESP-IDF Basics - Lecture 2

Part 5: ESP-IDF Basics - Assign. 2.1

Part 6: ESP-IDF Basics - Assign. 2.2

Part 7: This Article

Part 8: ESP-IDF Basics - Lecture 3

Part 9: ESP-IDF Basics - Assign. 3.1

Part 10: ESP-IDF Basics - Assign. 3.2

Part 11: ESP-IDF Basics - Assign. 3.3

This assignment is optional. You can do it if you still have time before the break.

Add another route to the HTTP server from the previous assignments:

POST /led/flash → accepts JSON {"periods": [int], "duty_cycles": [int]} and for each element, calculates the on-time and off-time and drives the LED accordingly.

To test a POST request, you need an app that allows you to send structured HTTP requests. One example is Teste. If you connect your computer to the module’s access point, you can instead use the Python script below.

Python script for POST request

Create the following script post_test.py

#!/usr/bin/env python3
"""
Send LED flashing parameters to an ESP device via HTTP POST.

Endpoint:
  POST http://192.168.4.1/led/flash
  Body: {"periods": [int, ...], "duty_cycles": [int, ...]}

Each pair (period, duty_cycle) defines one blink pattern.
"""

import requests
import json

# --- Configuration ---
ESP_IP = "192.168.4.1"  # Replace with your module’s IP address
ENDPOINT = f"http://{ESP_IP}/led/flash"

# Example data:
# periods in milliseconds, duty_cycles in percentage
payload = {
    "periods": [1000, 500, 2000],
    "duty_cycles": [50, 75, 25]
}

def send_led_flash(payload):
    """Send POST request to the ESP endpoint with LED flash parameters."""
    try:
        print(f"Sending POST to {ENDPOINT} ...")
        response = requests.post(ENDPOINT, json=payload, timeout=5)
        response.raise_for_status()
        print("✅ Request successful!")
        print("Response:", response.text)
    except requests.exceptions.RequestException as e:
        print("❌ Error communicating with the ESP:", e)

if __name__ == "__main__":
    print("Payload:", json.dumps(payload, indent=2))
    send_led_flash(payload)

Open an ESP-IDF Terminal ESP-IDF: Open ESP-IDF Terminal
Run the script python post_test.py

Solution outline
#

You need to check that both periods and duty_cycles have the same length and contain positive number only. duty_cycles should contain numbers between 0 and 100.
You can traverse the two arrays and calculate for each element at index i the LED on_time and off_time as follows:
```
on_time[i] = duty_cycle[i]/100 * periods[i]
off_time[i] = periods[i]-on_time[i]
```

You can drive the LED according to the sequence:

ON: on_time[1]
OFF: off_time[1]
ON: on_time[2]
OFF: off_time[2]
...

Conclusion
#

If you managed to reach this point, it means you have good understanding of a basic REST API implementation. You can now move to the third lecture, detailing the management of external libraries and the use of the components found on the component registry.