Glasses and Watch BLE on Raspberry Pi 4B

This project is to automatically stream data from the captivates glasses and equinox smartwatch to this device when they are in range.

Important Notes

1. The led turns on when either the watch or glasses are disconnected, and blinks when they both successfully connect before turning off. This behavior can be changed to just indicate for glasses connection with the `LEDINDICATE` global
2. The peripheral LED on the glasses resets on the first watch time guess, and uses a subsequent time guess to indicate the LED has been seen to restart the process. This code might need to change for the experiment; also, the delay and variability (how long it takes after a time guess for the LED to transition) is set in `gLEDMIN` and `gLEDMINVARIANCE` globals.
3. There *may* be a memory leak with the read connection/callback (we don't assign it to a variable and null it on disconnect). After profiling it doesn't seem to be a big deal (it would be a slow leak just on disconnect/reconnect), but it may be worth assigning the notify connection to a variable, striking the subscription, and nulling the reference.
4. The log current logs every time a packet is received, which is monstorous. We need to turn this off; perhaps we can log packet statistics every n seconds.
5. file writes max out at 12500 records, which is a pretty big file (~10MB). When we don't hit 12500 records in 4 hours we still write a file (i.e. if just watch data is streaming); we also write a file when the glasses disconnect. These settings can be modified with some of the globals.
6. It would be nice to add a socketio websocket server here to stream data live, and to work with the E4 streaming server as well. Major to-do item.

Setup

Raspberry Pi 4B has bluetooth 5.0 built-in, and it is working.

We're using bluez 5.55 (btmon -v) which came stock, and turned off default bluetooth:

sudo apt-get install bluetooth bluez libbluetooth-dev libudev-dev btusb
//check the verison installed
bluetoothd -v
sudo systemctl stop bluetooth
sudo systemctl disable bluetooth

To run, sometimes if the hci interface is in a bad state it can help to reset it:

sudo hciconfig hci0 down; sleep 0.2; sudo hciconfig hci0 up; sleep 0.2; sudo node test_ble.js

Always on with PM2

this needs to run as root because of HCI/BLE permissions. PM2 is used to run on startup and to maintain the script.

sudo npm install pm2@latest -g
sudo pm2 start stream_and_save.js
sudo pm2 startup
sudo pm2 save

process list in /root/.pm2/dump.pm2

script in /etc/systemd/pm2-root.service

logs in /root/.pm2/logs/

monitor with sudo pm2 monit

other useful commands:

//scan for BLE devices
sudo hcitool -i hci0 lescan
//reset BLE interface, especially if cntrl+C out of a command
sudo hciconfig hci0 down
sudo hciconfig hci0 up
//connects to BLE device and gives interactive prompt ('connect', 'primary'
subcommands will allow connection from command-line)
sudo gatttool -i hci0 -b 80:E1:26:24:87:8D --interactive
//within gatttool
connect
mtu 512
char-desc
char-write-cmd 0x0019 00000000FDFD00000000000000FDFD000000
char-write-cmd 0x0019 00000000FD0000000000000000FD00000000
char-write-cmd 0x0019 0000000000FD0000000000000000FD000000

power button

I also added a power button with LED (a Wendry Chassis NO button with LED) using https://github.com/fabiosoft/pi-power-button with all reset button GPIO commands commented out before installing.