# Bluetooth & Glance Clock

> "A short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances using UHF radio waves."

## General

Key facts:
- range up to 10 meters
- master and slave
- bluetooth radio needed (internal/dongle)

## Glance Clock

> Glance clock uses Bluetooth Low Energy (BLE) on your smartphone. Your phone pushes new data to the Glance clock when it is available

> Glance is not always connected to your phone. Your phone connects to your Glance at the moment the information is ready to be displayed or updated on the clock face. At the rest of the time, your Glance is disconnected from your phone.

> At this moment it is not possible. But we are planning to make an open API in the near future.

The Glance Clock is a BLE Peripheral/Slave with GATT server. Our service connecting to it would be the BLE Central/Master aka GATT client.

[glance-clock by Hypfer](https://github.com/Hypfer/glance-clock) is a collection of information of how to communicate with the clock via BLE.

For this you will need something like [pygatt](https://github.com/peplin/pygatt). It lets you connect to a GATT server - which the clock is - from devices like a RaspberryPi.

### Steps

1. Connect with device
1. Authenticate
1. Send command

### Example command

`gatttool --sec-level=high -b CLOCK_MAC -t random --char-write-req -a 0x001f -n 023000002203120141`

This sends a `Notify` command with a serialized `Notice` message. It will display the letter `A`, play the default notice sound `General_alert_1` as well as the default animation `Pulse` in the default color Lime

gatttool 
  --sec-level=high 
  -b CLOCK_MAC // Glance Clock address
  -t random // LE address type
  --char-write-req 
  -a 0x001f // Letter A
  -n 023000002203120141 // Notice message