Bluetooth Sensor Capture - Adafruit Circuit Playground Bluefruit¶
The following example demonstrates using an Adafruit Circuit Playground Bluefruit as a wireless sensor. The CircuitPython program uses only the onboard sensor hardware. The companion Python program runs on a host computer (e.g. desktop or laptop) and receives data. One example use case is to capture accelerometer motion sensor data for analysis.
Prerequisites
host computer with Python 3 Installation including BLE libraries
Adafruit Circuit Playground Bluefruit microcontroller board
Related Information
Site pages
Tutorials
Technical Documentation
- Adafruit BLE Library - API Reference
This reference applies to
adafruit_ble
module which is implemented for both the microcontroller and for host Python.
iOS apps
- Bluefruit Connect iOS App for iPad, iPhone, and Apple Watch.
This appears to be a somewhat general user interface tool. Adafruit has a related tutorial.
- Bluefruit Playground iOS App for iPhone.
This appears to be more of a remote control demo rather than a general purpose utility.
Contents
CircuitPython Remote Sensor¶
Direct download: cpb_ble_sensor.py.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | # cpb_ble_sensor.py
# Provide a remote sensing service over Bluetooth Low-Energy (BLE).
# This runs on an Adafruit Circuit Playground Bluefruit.
# This example works with either:
# 1. host_ble_receiver.py running on a host computer
# 2. the Plotter function of the Bluefruit Connect iOS app
# ----------------------------------------------------------------
# Import the standard Python time functions.
import time
# Import the board-specific input/output library.
from adafruit_circuitplayground import cp
# Import the Adafruit Bluetooth library. Technical reference:
# https://circuitpython.readthedocs.io/projects/ble/en/latest/api.html
from adafruit_ble import BLERadio
from adafruit_ble.advertising.standard import ProvideServicesAdvertisement
from adafruit_ble.services.nordic import UARTService
# ----------------------------------------------------------------
# Initialize global variables for the main loop.
ble = BLERadio()
uart = UARTService()
advertisement = ProvideServicesAdvertisement(uart)
# Flags for detecting state changes.
advertised = False
connected = False
# The sensor sampling rate is precisely regulated using the following timer variables.
sampling_timer = 0.0
last_time = time.monotonic()
sampling_interval = 0.10
# ----------------------------------------------------------------
# Begin the main processing loop.
while True:
# Read the accelerometer at regular intervals. Measure elapsed time and
# wait until the update timer has elapsed.
now = time.monotonic()
interval = now - last_time
last_time = now
sampling_timer -= interval
if sampling_timer < 0.0:
sampling_timer += sampling_interval
x, y, z = cp.acceleration
else:
x = None
if not advertised:
ble.start_advertising(advertisement)
print("Waiting for connection.")
advertised = True
if not connected and ble.connected:
print("Connection received.")
connected = True
cp.red_led = True
if connected:
if not ble.connected:
print("Connection lost.")
connected = False
advertised = False
cp.red_led = False
else:
if x is not None:
uart.write(b"%.3f,%.3f,%.3f\n" % (x, y, z))
|
Host Sensor Receiver¶
The host-side script uses a version of the Adafruit Bluetooth libraries for regular Python so the essential code uses the same interface.
Direct download: host_ble_receiver.py.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | # Connect to a remote sensing service over Bluetooth Low-Energy (BLE). This
# script runs in Python 3 on a desktop or laptop. It scans for a connection,
# the prints incoming data to the console until the connection breaks.
# It assumes the following packages have been installed:
#
# pip3 install adafruit-blinka-bleio
# pip3 install adafruit-circuitpython-ble
# ----------------------------------------------------------------
# Import the Adafruit Bluetooth library, part of Blinka. Technical reference:
# https://circuitpython.readthedocs.io/projects/ble/en/latest/api.html
from adafruit_ble import BLERadio
from adafruit_ble.advertising.standard import ProvideServicesAdvertisement
from adafruit_ble.services.nordic import UARTService
# ----------------------------------------------------------------
# Initialize global variables for the main loop.
ble = BLERadio()
uart_connection = None
# ----------------------------------------------------------------
# Begin the main processing loop.
while True:
if not uart_connection:
print("Trying to connect...")
for adv in ble.start_scan(ProvideServicesAdvertisement):
if UARTService in adv.services:
uart_connection = ble.connect(adv)
print("Connected")
break
ble.stop_scan()
if uart_connection and uart_connection.connected:
uart_service = uart_connection[UARTService]
while uart_connection.connected:
print(uart_service.readline().decode("utf-8").rstrip())
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