handshake: how to use the system

Please see the handshake project page for details of this project. The instructions given below explain how to set the system up.

Summary

Connect a USB to 3.5mm converter cable e.g. the Joycable to your communication device. Connect this converter cable with the receiver using a 3.5mm plug to plug mono audio cable. Power the receiver through the USB C socket. See the photo below.

Turn on the watch using a long press on the button.

Shake the watch gently and check that this is detected as a switch by the receiver unit.

Adjust the level of shake that will trigger a switch action using the jog dial on the receiver, followed by a long press on the button in the middle of the jog dial. This sends the new shake detection threshold to the watch.

handshake components

The handshake system comprises two parts, a smart watch and a receiver unit. See the photo below.

For a full explanation of how the system works, please read the project page at mattoppenheim.com/handshake.

Setting up the watch

The image below shows the side of the watch.

The silver cover is on top of a mini-USB socket. The USB socket is used to charge the watch and to program new firmware onto the watch. The cover over the USB socket is a little tricky to get off. The cover will not drop off the watch when it is opened as it is attached to the watch by a hinge.

Next to the USB socket cover is an on/off button.

To turn the watch on or off: press the button for about 3 seconds.

This button on the watch rotates but the rotation has no functionality. There is no touch interface on the watch. This functionality may be added in a later version of the software if is looks like it could be useful.

When the watch turns on it displays a message ‘Hello T-Watch’ before starting the handshake program.

When the watch has booted up, which takes a few seconds, you will see the display below:

The top slider displays shows the current amount of shake that is detected by the watch. This updates real time.

The bottom slider displays the amount of shake necessary to operate your communication software. The value for this threshold is displayed on the watch screen as ‘shake trigger: xxx’ where xxx is a number that varies from 525 to 1000 (these limits may change). For initial testing, we will probably work at the lower range of these values.

As the watch is moved around, the top slider will display real-time how much shake force is being detected by the shake sensor inside the watch. Once the top slider is to the right of the bottom slider, the shake detection is triggered. I’ve added an algorithm to try and filter out intended mild shakes from unintended violent shakes. No doubt, this bit of code will need tuning.

When an intended shake is detected this display is shown on the watch:

When an unintended violent shake is detected this display is shown on the watch:

To charge the watch, attach a USB cable to the micro USB socket in the side of the watch and connect to a USB socket or charger. For whatever reason, once the watch battery is at 0% it stays at 0% for an age while charging then starts ramping up to 100% fairly quickly. I don’t know how to improve this yet.

Setting up the receiver unit

The T-Embed receiver unit is powered from the USB-C socket on its side. The power can come from a standard USB socket or from a battery bank. The receiver connects to a 3.5mm to USB converter such as a Joycable. See the figure below.

Note: The first release of the receiver unit only works with a mono audio cable. Please check the image below and make sure that you are using a cable that looks like the one on the left. Later revisions will work with a stereo cable as well as a mono cable. This is one of many things that should have been simple to fix but turned out not to be!

The receiver has a jog dial around the button. This dial is used to adjust the trigger threshold. Use the dial to set a new trigger threshold then send this new value to the watch by giving a long press (about 2s) to the button in the middle of the dial. Turning the jog wheel clockwise will increase the amount of shake needed to send a trigger to your communication device, turning the jog wheel anti-clockwise decreases the amount of shake needed to send a trigger to your communication device. The updated trigger will not take effect in the watch until you give a long press on the button though. Check the watch to see that the new shake value is shown on the watch display.

The button on the receiver has three uses:

A long press: The receiver sends the trigger threshold shown on the receiver display to the watch.

A short press: The unit receives the greatest shake value for the last 5s from the watch so you can tune in the right trigger level.

A double tap: Sends a trigger signal from the receiver through the 3.5mm socket so you can check that your communication device responds.