# BLE Heart Rate Measurement example

(See the README.md file in the upper level 'examples' directory for more information about examples.)

This example creates GATT server demonstrating standard Heart Rate measurement service. It simulates Hear rate measurement and notifies to client when the notifications are enabled.

It uses ESP32's Bluetooth controller and NimBLE stack based BLE host

This example aims at understanding notification subscriptions and sending notifications.

To test this demo, any BLE scanner app can be used.

A Python based utility `blehr_test.py` is also provided (which will run as a BLE GATT Client) and can be used to test this example.   

Note :

* Make sure to run `python -m pip install --user -r $IDF_PATH/requirements.txt -r $IDF_PATH/tools/ble/requirements.txt` to install the dependency packages needed.
* Currently this Python utility is only supported on Linux (BLE communication is via BLuez + DBus).


## How to use example

### Configure the project

```
idf.py menuconfig
```

### Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

```
idf.py -p PORT flash monitor
```

(To exit the serial monitor, type ``Ctrl-]``.)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

## Example Output

This console output can be observed when blehr is connected to client and client enables notifications:

```
I (91) BTDM_INIT: BT controller compile version [fe7ced0]
I (91) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (181) phy: phy_version: 4100, 6fa5e27, Jan 25 2019, 17:02:06, 0, 0
I (421) NimBLE_BLE_HeartRate: BLE Host Task Started
GAP procedure initiated: stop advertising.
Device Address: xx:xx:xx:xx:xx:xx
GAP procedure initiated: advertise; disc_mode=2 adv_channel_map=0 own_addr_type=0 adv_filter_policy=0 adv_itvl_min=0 adv_itvl_max=0
connection established; status=0
subscribe event; cur_notify=1
 value handle; val_handle=3
I (21611) BLE_GAP_SUBSCRIBE_EVENT: conn_handle from subscribe=0
GATT procedure initiated: notify; att_handle=3
GATT procedure initiated: notify; att_handle=3
GATT procedure initiated: notify; att_handle=3
GATT procedure initiated: notify; att_handle=3
GATT procedure initiated: notify; att_handle=3
GATT procedure initiated: notify; att_handle=3
GATT procedure initiated: notify; att_handle=3

```

## Running Python Utility

```
python blehr_test.py
```

## Python Utility Output

This is this output seen on the python side on successful connection:

```
discovering adapter...
bluetooth adapter discovered
powering on adapter...
bluetooth adapter powered on

Started Discovery

Connecting to device...

Connected to device

Services

[dbus.String(u'00001801-0000-1000-8000-00805f9b34fb', variant_level=1), dbus.String(u'0000180d-0000-1000-8000-00805f9b34fb', variant_level=1), dbus.String(u'0000180a-0000-1000-8000-00805f9b34fb', variant_level=1)]

Subscribe to notifications: On
dbus.Array([dbus.Byte(6), dbus.Byte(90)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(91)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(92)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(93)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(94)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(95)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(96)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(97)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(98)], signature=dbus.Signature('y'), variant_level=1)
dbus.Array([dbus.Byte(6), dbus.Byte(99)], signature=dbus.Signature('y'), variant_level=1)

Subscribe to notifications: Off
Success: blehr example test passed

exiting from test...
disconnecting device...
device disconnected
powering off adapter...
bluetooth adapter powered off
```