MicroPython/ESP32-C3 Exercise: send/receive command via BLE UART

My former post show steps to MicroPython bluetooth (BLE) exampls, run on ESP32-C3. It's modified to send and receive command to control onboard LED remotely.

ble_simple_peripheral_LED.py (modified from ble_simple_peripheral.py) run on AI-Thinker NodeMCU ESP-C3-32S-Kit, act to be BLE Peripheral.

ble_simple_central_button.py (modified from ble_simple_central.py) run on Espressif ESP32-C3-DevKitM-1, act to be BLE Central.

Both flashed with MicroPython v1.19.1 frameware. ble_advertising.py have to be saved on both central/peripheral MicroPython device.

Once connected, user pressed central's onboard button to send command to peripheral via BLE UART, to toggle peripheral onboard LED.

In peripheral side, turn ON/OFF onboard LED according to received command, and send back the command to central, to control central's onboard LED. 

Once central receive command, turn ON/OFF onboard LED accordingly.

related:
~ MicroPython/NodeMCU ESP-C3-32S-Kit to control onboard LEDs
~ MicroPython/ESP32-C3-DevKitM-1 exercise: onboard BOOT button, and RGB LED (Neopixel)

ble_simple_peripheral_LED.py

"""
MicroPython(v1.19.1) exercise
run on AI-Thinker NodeMCU ESP-C3-32S-Kit
act as BLE UART periperhal.

Receive command from central, turn on/off onboard LED,
and send back the command to central.

Modified from MicroPython ble_simple_peripheral.py example
https://github.com/micropython/micropython/
blob/master/examples/bluetooth/ble_simple_central.py

"""

# This example demonstrates a UART periperhal.

import bluetooth
import random
import struct
import time
from ble_advertising import advertising_payload
from machine import Pin

from micropython import const

CMD_LEDON = b'LEDON\r\n'
CMD_LEDOFF = b'LEDOFF\r\n'

# NodeMCU ESP-C3-32S-Kit onboard LEDs assignment
pinR = Pin(3, Pin.OUT)
pinG = Pin(4, Pin.OUT)
pinB = Pin(5, Pin.OUT)

_IRQ_CENTRAL_CONNECT = const(1)
_IRQ_CENTRAL_DISCONNECT = const(2)
_IRQ_GATTS_WRITE = const(3)

_FLAG_READ = const(0x0002)
_FLAG_WRITE_NO_RESPONSE = const(0x0004)
_FLAG_WRITE = const(0x0008)
_FLAG_NOTIFY = const(0x0010)

_UART_UUID = bluetooth.UUID(
    "6E400001-B5A3-F393-E0A9-E50E24DCCA9E")
_UART_TX = (
    bluetooth.UUID(
        "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"),
    _FLAG_READ | _FLAG_NOTIFY,
)
_UART_RX = (
    bluetooth.UUID(
        "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"),
    _FLAG_WRITE | _FLAG_WRITE_NO_RESPONSE,
)
_UART_SERVICE = (
    _UART_UUID,
    (_UART_TX, _UART_RX),
)


class BLESimplePeripheral:
    def __init__(self, ble, name="mpy-uart"):
        self._ble = ble
        self._ble.active(True)
        self._ble.irq(self._irq)
        ((self._handle_tx,
          self._handle_rx),) \
          = self._ble.gatts_register_services(
              (_UART_SERVICE,))
        self._connections = set()
        self._write_callback = None
        self._payload = \
                      advertising_payload(
                          name=name, services=[_UART_UUID])
        self._advertise()

    def _irq(self, event, data):
        # Track connections so we can send notifications.
        if event == _IRQ_CENTRAL_CONNECT:
            conn_handle, _, _ = data
            print("New connection", conn_handle)
            self._connections.add(conn_handle)
        elif event == _IRQ_CENTRAL_DISCONNECT:
            conn_handle, _, _ = data
            print("Disconnected", conn_handle)
            self._connections.remove(conn_handle)
            # Start advertising again to allow a new connection.
            self._advertise()
        elif event == _IRQ_GATTS_WRITE:
            conn_handle, value_handle = data
            value = self._ble.gatts_read(value_handle)
            if (value_handle == self._handle_rx and
                self._write_callback):
                self._write_callback(value)

    def send(self, data):
        for conn_handle in self._connections:
            self._ble.gatts_notify(conn_handle,
                                   self._handle_tx,
                                   data)

    def is_connected(self):
        return len(self._connections) > 0

    def _advertise(self, interval_us=500000):
        print("Starting advertising")
        self._ble.gap_advertise(interval_us,
                                adv_data=self._payload)

    def on_write(self, callback):
        self._write_callback = callback

def Turn_LED(val):
    pinR.value(val)
    pinG.value(val)
    pinB.value(val)

def demo():
    ble = bluetooth.BLE()
    p = BLESimplePeripheral(ble)

    def on_rx(v):
        # command received from central,
        # turn ON/OFF LED accoringly,
        # and send back the command to centrol.
        print("RX", v)
        
        if v == CMD_LEDON:
            Turn_LED(1)
            print("command received: ", CMD_LEDON)
            p.send("from peripheral:")
            p.send(CMD_LEDON)
        elif v == CMD_LEDOFF:
            Turn_LED(0)
            print("command received: ", CMD_LEDOFF)
            p.send("from peripheral:")
            p.send(CMD_LEDOFF)

    p.on_write(on_rx)

    i = 0
    while True:
        """
        if p.is_connected():
            # Short burst of queued notifications.
            for _ in range(3):
                data = str(i) + "_"
                print("TX", data)
                p.send(data)
                i += 1
        """
        time.sleep_ms(100)


if __name__ == "__main__":
    demo()

ble_simple_central_button.py

"""
MicroPython(v1.19.1) exercise
run on Espressif ESP32-C3-DevKitM-1 
act as BLE UART central.

Detect onboard BOOT button,
send command to peripheral to toggle peripheral onboard LED.
and receive command from peripheral, turn on/off onboard.

* No debouncing for BOOT button detection here.

Modified from MicroPython ble_simple_central.py example
https://github.com/micropython/micropython/
blob/master/examples/bluetooth/ble_simple_peripheral.py

"""

# This example finds and connects to a peripheral running the
# UART service (e.g. ble_simple_peripheral.py).

import bluetooth
import random
import struct
import time
import micropython
import machine
import neopixel

from ble_advertising import decode_services, decode_name

from micropython import const

CMD_LEDON = b'LEDON\r\n'
CMD_LEDOFF = b'LEDOFF\r\n'

button_BOOT = machine.Pin(9,
                          machine.Pin.IN,
                          machine.Pin.PULL_UP)
np = neopixel.NeoPixel(machine.Pin(8), 1)

# To turn OFF peripheral LED in first power-up
current_led_val = True
root_button_pressed = True

# Turn OFF onboard RGB
np[0] = (0, 0, 0)
np.write()

def boot_pressed_handler(pin):
    global root_button_pressed
    root_button_pressed = True
    
button_BOOT.irq(trigger=machine.Pin.IRQ_FALLING,
                handler=boot_pressed_handler)

_IRQ_CENTRAL_CONNECT = const(1)
_IRQ_CENTRAL_DISCONNECT = const(2)
_IRQ_GATTS_WRITE = const(3)
_IRQ_GATTS_READ_REQUEST = const(4)
_IRQ_SCAN_RESULT = const(5)
_IRQ_SCAN_DONE = const(6)
_IRQ_PERIPHERAL_CONNECT = const(7)
_IRQ_PERIPHERAL_DISCONNECT = const(8)
_IRQ_GATTC_SERVICE_RESULT = const(9)
_IRQ_GATTC_SERVICE_DONE = const(10)
_IRQ_GATTC_CHARACTERISTIC_RESULT = const(11)
_IRQ_GATTC_CHARACTERISTIC_DONE = const(12)
_IRQ_GATTC_DESCRIPTOR_RESULT = const(13)
_IRQ_GATTC_DESCRIPTOR_DONE = const(14)
_IRQ_GATTC_READ_RESULT = const(15)
_IRQ_GATTC_READ_DONE = const(16)
_IRQ_GATTC_WRITE_DONE = const(17)
_IRQ_GATTC_NOTIFY = const(18)
_IRQ_GATTC_INDICATE = const(19)

_ADV_IND = const(0x00)
_ADV_DIRECT_IND = const(0x01)
_ADV_SCAN_IND = const(0x02)
_ADV_NONCONN_IND = const(0x03)

_UART_SERVICE_UUID = bluetooth.UUID(
    "6E400001-B5A3-F393-E0A9-E50E24DCCA9E")
_UART_RX_CHAR_UUID = bluetooth.UUID(
    "6E400002-B5A3-F393-E0A9-E50E24DCCA9E")
_UART_TX_CHAR_UUID = bluetooth.UUID(
    "6E400003-B5A3-F393-E0A9-E50E24DCCA9E")


class BLESimpleCentral:
    def __init__(self, ble):
        self._ble = ble
        self._ble.active(True)
        self._ble.irq(self._irq)

        self._reset()

    def _reset(self):
        # Cached name and address from a successful scan.
        self._name = None
        self._addr_type = None
        self._addr = None

        # Callbacks for completion of various operations.
        # These reset back to None after being invoked.
        self._scan_callback = None
        self._conn_callback = None
        self._read_callback = None

        # Persistent callback for when new data is
        # notified from the device.
        self._notify_callback = None

        # Connected device.
        self._conn_handle = None
        self._start_handle = None
        self._end_handle = None
        self._tx_handle = None
        self._rx_handle = None

    def _irq(self, event, data):
        if event == _IRQ_SCAN_RESULT:
            addr_type, addr, adv_type, rssi, adv_data = data
            if (adv_type in (_ADV_IND, _ADV_DIRECT_IND) and
                _UART_SERVICE_UUID in decode_services(adv_data)):
                # Found a potential device, remember it
                # and stop scanning.
                self._addr_type = addr_type
                self._addr = bytes(
                    addr
                )  # Note: addr buffer is owned by caller so
                   # need to copy it.
                self._name = decode_name(adv_data) or "?"
                self._ble.gap_scan(None)

        elif event == _IRQ_SCAN_DONE:
            if self._scan_callback:
                if self._addr:
                    # Found a device during the scan
                    # (and the scan was explicitly stopped).
                    self._scan_callback(self._addr_type,
                                        self._addr,
                                        self._name)
                    self._scan_callback = None
                else:
                    # Scan timed out.
                    self._scan_callback(None, None, None)

        elif event == _IRQ_PERIPHERAL_CONNECT:
            # Connect successful.
            conn_handle, addr_type, addr = data
            if addr_type == self._addr_type and addr == self._addr:
                self._conn_handle = conn_handle
                self._ble.gattc_discover_services(self._conn_handle)

        elif event == _IRQ_PERIPHERAL_DISCONNECT:
            # Disconnect (either initiated by us or the remote end).
            conn_handle, _, _ = data
            if conn_handle == self._conn_handle:
                # If it was initiated by us, it'll already be reset.
                self._reset()

        elif event == _IRQ_GATTC_SERVICE_RESULT:
            # Connected device returned a service.
            conn_handle, start_handle, end_handle, uuid = data
            print("service", data)
            if conn_handle == self._conn_handle and uuid == _UART_SERVICE_UUID:
                self._start_handle, self._end_handle = start_handle, end_handle

        elif event == _IRQ_GATTC_SERVICE_DONE:
            # Service query complete.
            if self._start_handle and self._end_handle:
                self._ble.gattc_discover_characteristics(
                    self._conn_handle,
                    self._start_handle,
                    self._end_handle
                )
            else:
                print("Failed to find uart service.")

        elif event == _IRQ_GATTC_CHARACTERISTIC_RESULT:
            # Connected device returned a characteristic.
            conn_handle, def_handle, value_handle, properties, uuid = data
            if (conn_handle == self._conn_handle and
                uuid == _UART_RX_CHAR_UUID):
                self._rx_handle = value_handle
            if (conn_handle == self._conn_handle and
                uuid == _UART_TX_CHAR_UUID):
                self._tx_handle = value_handle

        elif event == _IRQ_GATTC_CHARACTERISTIC_DONE:
            # Characteristic query complete.
            if self._tx_handle is not None and self._rx_handle is not None:
                # We've finished connecting and discovering device,
                # fire the connect callback.
                if self._conn_callback:
                    self._conn_callback()
            else:
                print("Failed to find uart rx characteristic.")

        elif event == _IRQ_GATTC_WRITE_DONE:
            conn_handle, value_handle, status = data
            print("TX complete")

        elif event == _IRQ_GATTC_NOTIFY:
            conn_handle, value_handle, notify_data = data
            if (conn_handle == self._conn_handle
                and value_handle == self._tx_handle):
                if self._notify_callback:
                    self._notify_callback(notify_data)

    # Returns true if we've successfully connected and
    # discovered characteristics.
    def is_connected(self):
        return (
            self._conn_handle is not None
            and self._tx_handle is not None
            and self._rx_handle is not None
        )

    # Find a device advertising the environmental sensor service.
    def scan(self, callback=None):
        self._addr_type = None
        self._addr = None
        self._scan_callback = callback
        self._ble.gap_scan(2000, 30000, 30000)

    # Connect to the specified device
    # (otherwise use cached address from a scan).
    def connect(self, addr_type=None, addr=None, callback=None):
        self._addr_type = addr_type or self._addr_type
        self._addr = addr or self._addr
        self._conn_callback = callback
        if self._addr_type is None or self._addr is None:
            return False
        self._ble.gap_connect(self._addr_type, self._addr)
        return True

    # Disconnect from current device.
    def disconnect(self):
        if not self._conn_handle:
            return
        self._ble.gap_disconnect(self._conn_handle)
        self._reset()

    # Send data over the UART
    def write(self, v, response=False):
        if not self.is_connected():
            return
        self._ble.gattc_write(self._conn_handle,
                              self._rx_handle, v,
                              1 if response else 0)

    # Set handler for when data is received over the UART.
    def on_notify(self, callback):
        self._notify_callback = callback
    
def demo():
    global root_button_pressed
    global current_led_val
    
    ble = bluetooth.BLE()
    central = BLESimpleCentral(ble)

    not_found = False
    
    def send_CMD(cmd):
        try:
            central.write(cmd, with_response)
        except:
            print("TX failed")

    def on_scan(addr_type, addr, name):
        if addr_type is not None:
            print("Found peripheral:", addr_type, addr, name)
            central.connect()
        else:
            nonlocal not_found
            not_found = True
            print("No peripheral found.")

    central.scan(callback=on_scan)

    # Wait for connection...
    while not central.is_connected():
        time.sleep_ms(100)
        if not_found:
            return

    print("Connected")
    
    def on_rx(v):
        # command received from peripheral,
        # update onboard RGB accordingly.
        print("RX", v)
        
        #convert memoryview to str
        cmd = str(v,'utf8')
        print(cmd)
        
        if v == CMD_LEDON:
            np[0] = (3, 3, 0)
            np.write()
        elif v == CMD_LEDOFF:
            np[0] = (0, 0, 0)
            np.write()
            

    central.on_notify(on_rx)

    with_response = False

    while central.is_connected():
        
        if root_button_pressed:
            # BOOT button pressed,
            # send command to peripheral to toggle LED
            root_button_pressed = False
            current_led_val = not current_led_val
            print("- root_button_pressed -", current_led_val)
            
            if current_led_val:
                send_CMD(CMD_LEDON)
                
            else:
                send_CMD(CMD_LEDOFF)

        time.sleep_ms(400 if with_response else 30)

    print("Disconnected")


if __name__ == "__main__":
    demo()