According to:
https://drive.google.com/file/d/0B4urklB65vaCcmFqOGRFWV9IR2s/view
The UUID's used by this module are:
Service: "0000ffe0-0000-1000-8000-00805f9b34fb”
Characteristic: “0000ffe1-0000-1000-8000-00805f9b34fb”
The easiest way to test this on the Raspberry Pi is to use the command line tool: "bluetoothctl".
Once you have launched the bluetoothctl tool, type "help" to get all the commands.
The basic ones to get you started will be "scan on", "scan off", "pair <mac_addr>", "connect <mac_addr>, "disconnect".
Pairing with the HC-08 module is a one-off setup, and I would do that with Bluetoothctl. To connect after that and write to the device, I would use the documented DBus API.
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/adapter-api.txt
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/device-api.txt
https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/gatt-api.txt
It looks like you want to do the Central Role and if you want to use Python there is the pydbus library which will help you greatly: https://pypi.org/project/pydbus/
Some useful things to know to get you started:
- The DBus service for bluez is called 'org.bluez'
- The Bluetooth adapter on a Raspberry Pi is normally '/org/bluez/hci0' DBus object path.
- The DBus Object path to a device is the adapter path plus the mac address prepended by 'dev_' and the semi-colons replaced with
underscores. i.e. 'DE:82:35:E7:43:BE' would be found at
'/org/bluez/hci0/dev_DE_82_35_E7_43_BE'
I don't have an HC-08 module so I've done an example connect, read, and write using a micro:bit. It should be fairly similar for you, you will need to change mac address and characteristic UUID.
import pydbus
bus = pydbus.SystemBus()
adapter = bus.get('org.bluez', '/org/bluez/hci0')
dev = bus.get('org.bluez', '/org/bluez/hci0/dev_DE_82_35_E7_43_BE')
# Get commands and properties available
print(dir(adapter))
print(dir(dev))
# Connect to the device if you have already paired the Raspberry Pi with it
dev.Connect()
To read and write you need to find the path to the characteristic which is a little more work. Typically you know the UUID of the characteristic you are interested in so to get the value from button A on a BBC micro:bit it would be:
mngr = bus.get('org.bluez', '/')
def get_characteristic_path(device_path, uuid):
mng_objs = mngr.GetManagedObjects()
for path in mng_objs:
chr_uuid = mng_objs[path].get('org.bluez.GattCharacteristic1', {}).get('UUID')
if path.startswith(device_path) and chr_uuid == uuid:
return path
char_path = get_characteristic_path(dev._path, 'e95dda90-251d-470a-a062-fa1922dfa9a8')
btn = bus.get('org.bluez', char_path)
btn.ReadValue({})
# [0]
Writing to a characteristic is similar. Here is an example of reading and writing to the Temperature Period on a BBC micro:bit
tmp_period_path = get_characteristic_path(dev._path, 'e95d1b25-251d-470a-a062-fa1922dfa9a8')
tmp_period = bus.get('org.bluez', tmp_period_path)
tmp_period.ReadValue({})
# Result is:
# [232, 3]
# To get it as an integer:
int.from_bytes(tmp_period.ReadValue({}), byteorder='little')
# 1000
# To write and new value of 1500
new_value = 1500
tmp_period.WriteValue(new_value.to_bytes(2, byteorder='little'), {})
tmp_period.ReadValue({})
# [220, 5]
