This project has sat on the backburner for quite sometime but I have been thinking about it alot over the last few months and in the last couple of days I have completely overhauled my approach and developed a complete electrical system architecture for an open source wheel chair. We are going to prototype this system and graft it to an existing wheelchair owned and operated by our fearless leader Tom !

A Block Diagram says a thousand words as I've always said, so here we go !! Here is the overall architecture of the system !!

To begin with an electric wheelchair electrical system isn't super complicated to begin with in terms of the physical hardware (custom safety rated firmware for all the embedded devices in the system is the biggest challenge), I distilled down the group discussions we have been having amongst our team and boiled it down to the architecture in the diagram.
You will notice that the biggest change there is no mention of the USB HID Black box device I was originally going to develop, I decided that I still want to do that, but I would rather make a custom Joystick shield for the Raspberry Pi that has the Joystick module and all the other controls/indicators the wheelchair user will need to operate their chair but also have the ability to interface with any USB HID device at the same time. This will allow use to build a traditional electric wheel chair control interface, but also allow us to audition and test many other off the shelf devices and explore what we can do with them for potential users. This is effectively going to be a complicated research platform in its first iteration and as we go I hope to develop it down into a completely integrated, robust, fully embedded RTOS based system with no Linux SoC require.

The overall architecture hinges on two pieces of custom hardware, and the rest are off the shelf components. A cool guy named James is designing a custom motor controller that will be able to driver all the different motors in the chair from a single PCB. The other piece of custom hardware is the Joystick/USB HID Wheelchair controller research platform, an RPi Hat that contains all the standard wheelchair controls, with the RPi being used for USB interfacing and Bluetooth interfacing.  The Joystick Hat will communicate with the Motor controller via RS485, the motor controller will also function as the power distribution board and send the bus voltage to the Joystick, the Hat board will have an integrated PSU to step down the bus voltage for all onboard devices.  The two off the shelf devices are the massive LifePoE battery with built in BMS, and the Bluetooth shunt used for monitoring and tracking the battery performance since it doesn't have any way for the BMS to report data to us.

Moving on to the main attraction !! I am designing the Joystick /USB HID hat! Like I said before and I will say it again, block diagram is worth 1000 words:

Basic Feature set:

- Classic Wheel Chair Joystick

- Dual Speed switch

- Variable speed switch (for fine tuning of speed)
- LED indicator for power/power level
- LED Indicator for Set speed
- USB configuration port, so the user can adjust all the operational parameters to their unique preferences/needs
- Optional Horn control

To make all this work I am designing a custom Hat PCB for the RPi, here is the block diagram and tech specs so far:

Tech Specs:
- RPi 3
- STM32F446RET6 ARM Cortex M4F MCU

-  JH-D202X-R2/R4 5K 10K Joystick module

- Ti DCDC Converters
- Switchcraft Mechanical Switches

That's all for now !