CleverHand - EMG

Here is the most recent form factor I am testing. It comprises a total of 11 modules, which results in 55 individual electrodes.

I use this opportunity to learn how to make some rendering on blender :D

Here the final result. I used FDM printing and flexible filament for the white curly band and I used SLA printing and transparent resin for the small protective case of each module.

SPI buses are very fast however the number of wires needed increases with the number of modules connected to the bus. In this project, we are limited by the number of connections as we cannot afford to have 3+16 lines just for communication.

A solution would be to create an addressing system to select a module on fewer buses. A standard addressing system requires a hard-coded address for each module. It could be done with pads to solder on each board to set their individual address. Unfortunately, this system is not very modular as it forces each module to be "differentiated".

A solution I came up with after chatting with my father is :

Addressing the module by their order on the bus.

The addressing system works on 4 wires. Each module read the 4 bits address present on the 4 wires and then increments by one the address for the following module. Each module is activated only if they read 0xF (0b1111, 15). Indeed, when the module tries to increment 0xf, it activates a carry bit connected to the chip select of the chip!

Here a schematics providing a visual explanation of the system:

Some pictures of the previous iterations of this project

From very simple analogue OpAmp circuits I designed to amplify a single EMG signal, I went to create modular multichannel digital devices!