The Itinerant Engineer

I received the completed boards from the cerebral palsy project from BatchPCB today. After soldering down all the components, I plugged it in, and it worked right away. As an unexpected bonus, I got eight free copies of the board—I’m guessing they had some free space on the production run, and decided to stick a few small ones (mine) in along the edges.

Next comes experiments with switching and software. I spoke about this project at Ignite last Thursday; I’ll post the talk here when it’s available. In the mean time, check out the media section for the slides.

On December 14, the gauntlet was thrown:

I challenge a team of you to design a computing device that enables people with mild to moderate cerebral palsy to contribute to society in meaningful and productive ways.

The challenge came from the Spastics Centre Kanpur. Grant money was offered, and The Nerd Herd—my high school friends, and me—went to work. Mike, Kurt, Mark, Jeff and I have been working on the project since December, and we have some results to show.

Cerebral Palsy

The project began with a trip to the library. Before I started any design work, I needed to understand the symptoms of the condition. I spent a few hours at the library with Cerebral Palsy: A Complete Guide for Caregiving, which I checked out and brought home. A few facts about cerebral palsy:

• CP is a congenital disorder (it is present at birth). In Freud’s time, CP was believed to be caused by asphyxiation during birth, but modern science has attributed the condition to fetal blood clots. Fetal trauma is sometimes responsible for the clots, but many cases have no discernible cause. Lifestyle factors are not a major cause of CP.
• Incidence: approximately 2 cases per 5000 births (0.4%). Prevalence does not vary by nation, but has risen slightly in all locations during the past 20-30 years.
• CP does not affect cognitive function. However (possibly due to a shared root cause), the condition is highly correlated with other mental disorders which, unfortunately, do impair cognitive function.
• Symptoms vary widely, but 70-80% of cases are spastic. Spastic CP is not treatable. Athetoid CP is less common, but better therapeutic methods have been developed to treat it. Generally, the disease causes impairment of motor function in one side of the body (hemiplegic cases), or in both legs. Some cases are quadriplegic, but they are less common.

Owing to the diversity of symptoms, we identified reconfigurability as an important factor. Also, we tried hard to keep cost down, to accommodate the budget of a person living in India. Finally, to ensure accessibility to a non-technical audience, we strove for ease of configuration. We chose not to sacrifice functionality for ease of use, believing that over time, a person would prefer a more functional device, even if it required a bit more upfront training (we might reconsider this decision later.)

The Design

After some brainstorming, we settled on a modified version of Objective Development’s HIDKeys. The HIDKeys codebase includes V-USB, a software-only USB stack for Atmel’s AVR line of processors. When plugged into a USB port, the device presents a standard USB human interface device to the operating system, requiring no drivers or configuration.

Using HIDKeys, we plan to attach a group of switches to the user’s body. We’re currently exploring novel input strategies including chording- and hotkey-based approaches; I’ll post the details when they become available.

Full code for the project will be made available as soon as we finish it (per the V-USB license terms). Right now, I’m working on getting a PCB cut.