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How to MQTTS (AWS IoT Core) Client Example (MicroPython)

This program demonstrates how to configure the W55RP20-S2E board as an MQTTS Client (OP=6) using a Raspberry Pi Pico (Host) via UART or SPI. It establishes a secure connection to AWS IoT Core using SSL/TLS certificates to publish and subscribe to messages.

Step 1: Prepare software

The following software is required to run and test the MicroPython example.

• Thonny : An integrated development environment for MicroPython. used to write, upload, and run code.
• AWS IoT Setup & Certificate Download:
• Please refer to the https://docs.wiznet.io/Product/Chip/MCU/Pre-programmed-MCU/W55RP20-S2E/mqtt-connection-guide-en#how-to-connect-to-aws-using-mqtt
• Following the link, you must create a "Thing" in the AWS IoT Console.
• Crucial: During the creation process, you must download the Device Certificate, Private Key, and the Amazon Root CA 1 file to your PC.

Step 2: Prepare hardware

1. Connect GPIO13 according to the selected UART/SPI mode of the W55RP20 EVB Pico, as illustrated below.

2. Connect the Raspberry Pi Pico and the W55RP20 EVB Pico using jumper wires as shown below, depending on the selected UART/SPI mode.

• Important Note on Mode Switching: In this example setup, GPIO 13 of the W55RP20 EVB Pico is physically connected to GPIO 13 of the Raspberry Pi Pico. The Host Pico sets the mode (High/Low) automatically based on the software configuration.
• If you change the MODE in the code (e.g., UART ↔ SPI): You MUST reset both boards (Raspberry Pi Pico and W55RP20 EVB Pico) to ensure the mode is switched and recognized correctly.

If UART mode :

If SPI mode :

3. Connect the Raspberry Pi Pico to your PC (desktop or laptop) using a 5-pin Micro USB cable.

4. Connect the W55RP20 EVB Pico to your PC (desktop or laptop) using a USB Type-C cable.

Step 3: Setup Example

• Raspberry Pi Pico (Master) : Getting started with Raspberry Pi Pico (MicroPython)

Please refer to the link below to install the MicroPython firmware on the Raspberry Pi Pico.

• W55RP20 EVB Pico : Getting started with W55RP20 EVB Pico

Please refer to the link below for instructions on how to use the W55RP20 S2E.

• Configure Certificates in Example Code : Before running the example, you must manually input the downloaded certificate data into 09_mqtts_client.py.

1. Open the downloaded certificate files (.pem or .txt) using a text editor (like Notepad).
2. Copy the text and paste it into the corresponding variables in the code.
3. Note: Ensure you include the \r\n line breaks as shown in the template to maintain the correct PEM format.

# 09_mqtts_client.py - Certificate Section

# Paste 'AmazonRootCA1.pem' content here
AWS_CA_CERT = (
    "-----BEGIN CERTIFICATE-----\r\n"
    "..."
    "-----END CERTIFICATE-----\r\n"
)

# Paste 'xxx-certificate.pem.crt' content here
AWS_CLIENT_CERT = (
    "-----BEGIN CERTIFICATE-----\r\n"
    "..."
    "-----END CERTIFICATE-----\r\n"
)

# Paste 'xxx-private.pem.key' content here
AWS_PRIVATE_KEY = (
    "-----BEGIN RSA PRIVATE KEY-----\r\n"
    "..."
    "-----END RSA PRIVATE KEY-----\r\n"
)

Step 4: Upload Code

• Raspberry Pi Pico

Open Thonny IDE and connect to the Raspberry Pi Pico. Upload the following driver and example files to the Pico's storage.

Required Files:

1. w55rp20_s2e_uart.py (Required for UART mode)
2. w55rp20_s2e_spi.py (Required for SPI mode)

Example Application Files (Choose one to test):

• 09_mqtts_client.py (The main application)

Configuration: Before running an example, open the Python file you intend to use and modify the User Configuration section at the top.

# 09_mqtts_client.py
#
# MQTTS (AWS IoT Core) example (Supports both SPI and UART modes):
# - Configure the module as MQTTS client (OP=6) + DHCP
# - Upload Root CA / Client Certificate / Private Key via AT commands
# - Publish initial message and receive subscribed topic data
#
# Select mode by changing the MODE variable below.

import time

# -------------------------------------------------------------------------
# Configuration
# -------------------------------------------------------------------------
MODE     = "spi"  # Set to "spi" or "uart"
USE_DHCP = True    # True: DHCP (IM=1), False: Static IP (IM=0)

# AWS IoT Settings
BROKER_HOST = "YOUR_AWS_ENDPOINT"
BROKER_PORT = "8883"
CLIENT_ID   = "w55rp20_aws_client"
SUB_TOPIC   = "sdk/test/python"
PUB_TOPIC   = "sdk/test/python1"
PUB_MESSAGE = "Hello from W55RP20-S2E to AWS IoT"
KEEP_ALIVE  = 60

# Network Configuration
LOCAL_IP    = "192.168.11.100"  # Local IP (Used when USE_DHCP=False)
SUBNET_MASK = "255.255.255.0"   # Subnet Mask (Used when USE_DHCP=False)
GATEWAY     = "192.168.11.1"    # Gateway (Used when USE_DHCP=False)
DNS_SERVER  = "8.8.8.8"         # DNS Server (Used when USE_DHCP=False)
.
.

Step 5: Testing with Mosquitto (PC Side)

Log in to AWS IoT Console: Navigate to Test > MQTT test client.

Monitor Incoming Messages:

• In the Subscribe to a topic tab, enter sdk/test/python1.
• Click Subscribe.

Prepare to Send Messages:

• In the Publish to a topic tab, enter sdk/test/python.
• Enter a message (e.g., {"message": "Hello from AWS IoT console"}).

# Send a message to the Pico
mosquitto_pub -h localhost -t w55rp20/sub -m "LED_ON"

Step 6: Run

Pico (Thonny):

• Open 09_mqtts_client.py.
• Run the script (F5).
• Wait for the TLS handshake (this takes longer than standard MQTT—about 15 seconds).

AWS IoT (Verify Publish):

• You should see "Hello from W55RP20-S2E to AWS IoT"

Pico (Thonny) : Verify Subscribe

• Publish a message from the AWS Console to sdk/test/python.
• You should see [RX] sdk/test/python : {"message": "Hello from AWS IoT console"} in the Thonny shell.