ra_ble.py

#
# Copyright reelyActive 2023-2024
# We believe in an open Internet of Things
#

import bluetooth


ble = bluetooth.BLE()
ble.active(True)


def send_value(value):
    # value is a percentage
    # we want a hex value btw 0 and 65535 (16-bits),
    # then split into TWO bytes (MSB and LSB)
    bitvalue = int(value * .01 * 65535)
    high = (bitvalue >> 8)
    low = (bitvalue & 0x00FF)

    # Advertising payload bytes:
    # 0:   0x05 = Length (not including the length byte itself)
    # 1:   0x16 = 16-bit service data (from GAP)
    # 2-3: 0x2af9 = 16-bit UUID of generic level characteristic (little endian)
    # 4-5: 0x1234 = 16-bit generic level value (little endian) 4660 / 65535 = 7.11%
    #_ADV_PAYLOAD = [ 0x05, 0x16, 0xf9, 0x2a, 0x34, 0x12 ]
    _ADV_PAYLOAD = [ 0x05, 0x16, 0xf9, 0x2a, low, high ]
    _ADV_INTERVAL_US = 500000 # 500000 microseconds = .5 seconds
    ble.gap_advertise(_ADV_INTERVAL_US, adv_data=bytearray(_ADV_PAYLOAD))