How to Perform an HTTP Request in MicroPython with a Pico W?

In this article, we will explore how to perform an HTTP request in MicroPython with a Pico W.

We will utilize the urequests module, which allows making HTTP requests in MicroPython.

Prerequisites before Getting Started with Pico W

To use the Pico W, you need to have the MicroPython firmware installed on your Pico W.

You can follow the tutorial below to install the MicroPython firmware on your Pico W: Install MicroPython on a Pico W.

To transfer files to the Pico W, you can use the software Thonny or PyCharm with the MicroPython plugin installed.

Connect Your Raspberry Pi Pico W to the Internet via Wi-Fi

To perform an HTTP request, you must connect your Pico W to the internet via Wi-Fi. We will use the network module from the MicroPython standard library to connect the Pico W to the internet.

import network
from time import sleep

ssid = SSID
password = PASSWORD

sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)

sta_if.connect(ssid, password)
while not sta_if.isconnected():
    sleep(1)
print('Connection successful')
print(sta_if.ifconfig())

In this code, we start by importing the network module from the MicroPython standard library. Next, we set the Wi-Fi network name and password in the ssid and password variables. Finally, we create an instance of the WLAN class and connect to the Wi-Fi network.

The while loop is used to wait for the Wi-Fi network connection to be established. Once the connection is established, we display the IP address of the Pico W.

This loop is crucial because without it, the following code will be executed before the Wi-Fi network connection is established.

To learn more about the network module, you can refer to the official documentation: network — network configuration.

Installing the urequests Module on Pico W

# Check if the urequests module is already present
try:
    import urequests
except ImportError:
    # If the module is not present, install micropython-urequests via upip
    import upip
    upip.install('micropython-urequests')

    # Import urequests again after installation
    import urequests

In this code, we use a try-except structure to check if the urequests module is already present. If importing generates an error (ImportError), it means the module is not installed. In this case, we use the upip module to install micropython-urequests. Then, we import the urequests module again to use it in the rest of the code.

Making an HTTP Request in MicroPython with a Pico W

Here is an example code demonstrating how to make an HTTP request in MicroPython with a Pico W to the Rutilus Data platform. The goal is to send a value to a time series using an HTTP POST request.

The post function from the urequests module is used to perform the HTTP request. It requires the request URL, the data to be transmitted, and the request headers.

The data to be sent must be in JSON format, for which the ujson module from the MicroPython standard library is used. It transforms a Python dictionary into JSON format. The request headers specify that the data is in JSON format.

Don't forget to replace "token_authentication" with the token of your device, which you can find on the corresponding page of your device on the Rutilus Data platform.

import urequests
import ujson

# Replace "token_authentification" with the token of your device
data = {"value": 1.0, "token": "token_authentification"}
url = "https://rutilusdata.fr/api/timeseries/"
headers = {'content-type': 'application/json'}

# Make the HTTP POST request
response = urequests.post(url, data=ujson.dumps(data), headers=headers)

# Get the response in JSON format
json_response = response.json()

# Show the response
print(json_response)

To interpret the response of the request, we use the json function from the urequests module. This function converts the response of the request into a MicroPython dictionary.

The complete source code is available on GitHub.