circuitpython/examples/bluetooth/ble_advertising.py

86 lines
2.6 KiB
Python

# Helpers for generating BLE advertising payloads.
from micropython import const
import struct
import bluetooth
# Advertising payloads are repeated packets of the following form:
# 1 byte data length (N + 1)
# 1 byte type (see constants below)
# N bytes type-specific data
_ADV_TYPE_FLAGS = const(0x01)
_ADV_TYPE_NAME = const(0x09)
_ADV_TYPE_UUID16_COMPLETE = const(0x3)
_ADV_TYPE_UUID32_COMPLETE = const(0x5)
_ADV_TYPE_UUID128_COMPLETE = const(0x7)
_ADV_TYPE_UUID16_MORE = const(0x2)
_ADV_TYPE_UUID32_MORE = const(0x4)
_ADV_TYPE_UUID128_MORE = const(0x6)
_ADV_TYPE_APPEARANCE = const(0x19)
# Generate a payload to be passed to gap_advertise(adv_data=...).
def advertising_payload(limited_disc=False, br_edr=False, name=None, services=None, appearance=0):
payload = bytearray()
def _append(adv_type, value):
nonlocal payload
payload += struct.pack('BB', len(value) + 1, adv_type) + value
_append(_ADV_TYPE_FLAGS, struct.pack('B', (0x01 if limited_disc else 0x02) + (0x00 if br_edr else 0x04)))
if name:
_append(_ADV_TYPE_NAME, name)
if services:
for uuid in services:
b = bytes(uuid)
if len(b) == 2:
_append(_ADV_TYPE_UUID16_COMPLETE, b)
elif len(b) == 4:
_append(_ADV_TYPE_UUID32_COMPLETE, b)
elif len(b) == 16:
_append(_ADV_TYPE_UUID128_COMPLETE, b)
# See org.bluetooth.characteristic.gap.appearance.xml
_append(_ADV_TYPE_APPEARANCE, struct.pack('<h', appearance))
return payload
def decode_field(payload, adv_type):
i = 0
result = []
while i + 1 < len(payload):
if payload[i + 1] == adv_type:
result.append(payload[i + 2:i + payload[i] + 1])
i += 1 + payload[i]
return result
def decode_name(payload):
n = decode_field(payload, _ADV_TYPE_NAME)
return str(n[0], 'utf-8') if n else ''
def decode_services(payload):
services = []
for u in decode_field(payload, _ADV_TYPE_UUID16_COMPLETE):
services.append(bluetooth.UUID(struct.unpack('<h', u)[0]))
for u in decode_field(payload, _ADV_TYPE_UUID32_COMPLETE):
services.append(bluetooth.UUID(struct.unpack('<d', u)[0]))
for u in decode_field(payload, _ADV_TYPE_UUID128_COMPLETE):
services.append(bluetooth.UUID(u))
return services
def demo():
payload = advertising_payload(name='micropython', services=[bluetooth.UUID(0x181A), bluetooth.UUID('6E400001-B5A3-F393-E0A9-E50E24DCCA9E')])
print(payload)
print(decode_name(payload))
print(decode_services(payload))
if __name__ == '__main__':
demo()