Tag: prototype

More (Smart) LEDs

The Talisman V2 is using the CPU already included in the WiFi radio.  This Wifi CPU has less control wires made available than what was available from the independent CPU controller in Talisman V1.

In Talisman V1 there were 3 full color LEDs. Each full color LED used 3 wires – one wire for each of the red, green and blue LEDs. Therefore the Talisman V1 had used 9 control wires. (3 sets of 3 wires.)

Smart LEDs are being used in Talisman V2 to reduce the number of control wires. A large number of smart LED can all be controlled from one single control wire.

(This is achieved by sending the necessary color data for all the RGB LEDs over the single wire into the first LED. The first led then daisy chains the data passed along to the next LED in the sequence.)

The image above shows a V1 Talisman LED that with 3 wires on the left. On the right animated image is single smart LED. It can be seen in the right hand side photo that the little 5mm square LED has a dark chip rectangle and tiny gold wires within the white package. Each smart LED in V2 comes with a little chip inbuilt!

So, this posts shares how it is possible to reduce the number of data control wire by the use of smart LEDs from 9 to 1.  In addition it is possible to daisy chain a very large number of smart LEDs in a long sequence.

It is intended to add additional full color LEDs onto the Talisman V2, most likely in a circular ring or oval layout. This should allow the Talisman V2 to be orientated anyway an artists chooses. The Talisman V1 only had LEDs on the front edge, so V1 had to be orientated a certain way when artistically mounting.

Prototyping the smartLEDs today, uncovered a downside; they use power even when no light is being emitted! In fact their little internal chip uses so much power even when dark that they would over time significantly reduce the battery life.   For this reason it is necessary for the Talisman V2 to switch power off for the LEDs unless they are going to be shining.

It so happens that there is already a spare switched power available on the Talisman V2. The Talisman V1 used to have a Bluetooth controller that had it’s power turned on and off. This bluetooth is no longer required, so the second switched power is now used for powering on and off all the smart LEDs on V2.


Replaceable Battery

The design revision for Talisman V2 includes the ability to replace the rechargeable battery without the need to solder. The Talisman V2 uses a plug in connector between the battery and the main circuit board.


This will allow the installation of a replacement battery without the need to solder the two battery wires.  The actual ability to replace the battery will depend on the case encapsulation used and choosen by the various artists.

In theory it should be possible to cut and peel away any silicon rubber case from Sugru. The actual reality of being able to remove whatever case is used is questionable. However assuming the artist’s case can be removed, the use of a connector removes the earlier requirement for soldering the battery.

The images show the battery with the plug on the end of the battery wires, and the white socket that is soldered onto the main electronic circuit board.



Version 2 – Upgraded CPU with WiFi

Initial feedback on the Talisman V1 confirmed the requirement to minimise size and simplify the usage.

If the Talisman were able to connect directly to WiFi this would simply the deployment because the use of a bridge would no longer be necessary.


A search of the available radio modules resulted in the selection of an extremely low cost WiFi module from ExpressIf in China. The ESP-07 WiFi module provides WiFi ability. The module can connect to an existing internet WiFi network as a client. This network would be a user’s home WiFi network, or a WiFi network shared from the users roving mobile handset. Most mobile devices can act as a AccessPoint, sharing their cellular mobile internet access on a password protected WiFi network. This is simple to use and just requires turning on on a mobile device.

The ESP-07 also can act as an Access Point. This is useful because it allows the module to provide a WiFi network that the user can connect to. A user could connect to the module in the Talisman V2 using their laptop or mobile phone. The user would simply select the Talisman V2 provided WiFi network from the list of available networks on their mobile or laptop.

Once a user connected to the Talisman V2 they could browse to a Talisman V2 provided web page and enter the details of their home network.

Having the Talisman V2 provide a WiFi network with a single simple web page for entering network name(s) and password(s) allows the user to configure the Talisman to use their password protected home WiFi network.

The ESP-07 WiFi module can obtain the RSSI signal strength of nearby WiFi networks. This will be used to detect the close physical proximity of the Talisman V2 to beacons.

The ESP-07 also provides access to store data and downloaded apps. The ESP-07 can be programmed to run the apps. Therefore using the ESP-07 would no longer require a seperate micro-controller. This reduces the number of components, and allows the design to be shrunk in size.

Given that the ESP-07 radio module provides WiFi and can use RSSI to detect nearby beacons, the Bluetooth module can be dropped from the hardware design.

It is proposed that the Talisman V2 would use the ESP-07 WiFi module and no longer require or support the use of bluetooth.

All the features mentioned above are being tested to ensure the functionality works as expected. A more comprehensive post will be made showing this version 2 parts prototype.

Demo Panel

The demo panel shown below was sent or display at the 2017 OMIP meeting.


The panel enables pushbutton triggering off events rom three key use cases to be seen and felt on the talisman prototype.

The demo panel also played a short audio file introducing the Connected Sangha project, and the Talisman. Videos of the panel were recorded but not able to be included within this post.

Status – Hardware and Firmware

The table below lists the current status of the hardware functional tasks and (when required) the corresponding firmware driver source code.

Function Hardware Firmware
Reverse protection for magnetic connector Tested not req.
Lithium-ion battery charging Tested todo
Battery level sensing Tested todo
Voltage regulation Tested not req.
In circuit device programming (dev only) Tested not req.
Microprocessor high speed operation Tested todo
Microprocessor sleep mode operation todo todo
Inbuilt flash storage reading todo todo
Inbuilt flash storage clearing and writing todo todo
Three full color LEDs 1 of 3 done todo
Bluetooth serial data link (master mode) todo todo
Bluetooth RSSI proximity measurement todo todo
Vibration motor todo todo
Accelerometer XYZ sensing todo todo
Accelerometer single tap detection todo todo
Accelerometer double tap detection todo todo
Bluetooth beacon with plug pack todo not req.
USB cable with BT and Win7 bridge program todo todo
Android Bluetooth bridge app todo todo

The not req. indicates that driver source code is not required for the particular functional area.

Final Prototype (in parcel)

The final resin cast talisman prototype was included in the parcel. Each item in the parcel has a descriptive note in each zip lock bag.


The included resin prototype had all components mounted inside clear resin to allow sculpturing the talisman shape. The final unit will be milky opaque and not clear.

The included prototype did not have a PCB included so one of the two nuts was loose and has been weakly glued in place. The final talisman will have the nut on the top side of the PCB and will not fall out because the PCB will hold it firmly in place.

The final device will be either bolted onto a custom personalised wrist strap, or will be worn around the neck as a pendant with a chain attacked to the rear of the talisman.

Power is applied to the device with a magnetic clasp once a week to recharge the device.