This code implements a Bluetooth Low Energy (BLE) communication interface for the ESP32 using the MicroPython ubluetooth module. It provides basic functionality to act as a BLE peripheral device with a custom service (Nordic UART Service). The ESP32 can advertise itself, accept connections from a central device (e.g., a smartphone), and exchange messages via the BLE protocol.
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__init__(self, name="ESP32_UART")
Purpose: Initialize the BLE functionality and set up the device's name and BLE configuration.
What it does: Activates BLE, sets up the interrupt handler, initializes variables, defines BLE services via register_services, and starts advertising with advertise.
This is the constructor that initializes the Bluetooth Low Energy (BLE) object. It sets the BLE device to active mode, assigns an interrupt handler (ble_irq), and configures its name. It initializes variables for the transmit (TX) and receive (RX) handles and connection state. It also calls register_services to define the BLE services and starts advertising to make the device discoverable.
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ble_irq(self, event, data)
Purpose: Handle various BLE events such as connection, disconnection, and data write.
What it does: If a device connects, it prints a connection message and sets the connection state to True. If a device disconnects, it prints a disconnection message, sets the connection state to False, and restarts advertising. If data is written to the RX characteristic, it decodes and prints the message, then sends an echo back to the central device.
This function handles BLE events. It reacts to specific events:
Event 1 (_IRQ_CENTRAL_CONNECT): Triggered when a device connects. It prints a connection message and sets self.connected to True. Event 2 (_IRQ_CENTRAL_DISCONNECT): Triggered when a device disconnects. It prints a disconnection message, sets self.connected to False, and restarts advertising. Event 3 (_IRQ_GATTS_WRITE): Triggered when data is written to the RX characteristic. It reads the received data, decodes it, and prints it. It also sends an echo message back using self.send.
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register_services(self)
Purpose: Define the BLE service and its characteristics.
What it does: Uses the Nordic UART Service (NUS) UUID to set up a service with two characteristics: RX (Receive): Allows the central device to send data to the ESP32. TX (Transmit): Allows the ESP32 to send notifications to the central device. Registers the service and stores the TX and RX handles for later use.
This function defines the BLE services and characteristics. It uses the Nordic UART Service (NUS) UUIDs for communication. The RX_UUID is for receiving data (write characteristic), and the TX_UUID is for sending data (notify characteristic). The service and its characteristics are registered with the BLE stack, and the handles for TX and RX are stored.
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send(self, message)
Purpose: Send a message to the connected central device.
What it does: Checks if a device is connected and uses the TX characteristic handle to send the message via BLE notifications.
This function sends a message to the connected central device using the TX characteristic. It ensures a connection exists before attempting to notify the central device.
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advertise(self)
Purpose: Make the ESP32 discoverable to BLE scanners.
What it does: Constructs advertising data, including the device name, and starts advertising for 100 seconds. Prints a message to indicate the device is advertising.
This function starts BLE advertising, making the device discoverable by nearby BLE scanners. It constructs advertising data that includes the device name and advertises it for 100 seconds. The function also prints a message to indicate the device is in advertising mode.
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ble = ESP32_BLE("ESP32_UART")
Purpose: Create an instance of the ESP32_BLE class.
What it does: Initializes the BLE setup with the name "ESP32_UART" and starts advertising.
This line creates an instance of the ESP32_BLE class, initializing the BLE device with the name "ESP32_UART."
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