JWC's Homepage
Hello
I'm JWC, an amateur programmer, web designer, hacker, MIT student, and general electronics enthusiast. This site is a repository for my hardware and software projects.
Latest Blog Post
ACRIS Board Rework: Fixing Faulty CommunicationA while back, I identified a major issue with ACRIS’s communication network. The MAX485 chips that I use can switch between transmitting data and receiving data. To switch modes, you simply pull two pins either high or low. I tied these pins directly to the ATMEGA so that I could allow the LED controllers to talk to each other in future firmware revisions.
However, when the ATMEGA first starts up, the state of this pin is unknown, so a blip in the logic power can cause multiple devices to want to transmit data. As a result, the entire communication network just sort of stops. 
But, by adding a simple pull-down resistor to those transmission-enable pins, it will make the default state of the MAX485 to receive data.
The rework on my lights was pretty difficult because everything was pretty tightly packed. But, I was able to remove the main body in order to get at the MAX485 chip.
Afterward, soldering a 10K pulldown resistor was not hard.
Re-assembling was a pain in the neck, though. I kept losing the plastic spacers and doodads.
News
I reorganized my projects and future projects. Also updated the menu a bit.
Finally. After months of inactivity, I finally have ACRIS ready enough to show the world. This post is more or less an account of what I’ve done so far. The main project page has links to all the technical information, plus a ton of photos, especially on the page about the lights I designed. I’m [...]
And we’re (more or less) back…
Wow. My last post was in late July. I’m not really sure what happened in August, but this semester has been hitting me repeatedly with a bag of bricks. Every time I think that I can spend a few hours working on personal projects, it turns out that I just forgot about something else that [...]
I’ve switched to RAM Host. If you see this message, then DNS information has propagated. I will leave my existing hosting up for a few days before I replace it with a redirection message (for anyone who still tried to use my old domain to go to my website). The old hosting will go away [...]
For some reason, I’ve been using 1024-bit DSA keys to sign my mail. It generally suggested that keys of at least 2048-bits be used for good security, so I have revoked the three keys I have been using (one for each email address) in favor of a single 3072-bit DSA/ElGamal key, which I will use [...]