If anyone's going to be at Engineering Open House this weekend at the University of Illinois, stop by Everitt 168 to see a demo of my project!

Post-EOH

My exhibit went fairly well considering this is the first time I've done anything of the sort. Of the visitors to my exhibit, there were several elementary/middle school groups, many middle school and high school students, alumni, and other adults. One of the goals of my exhibit was to get visitors to see calculators in a new light (no pun intended), and I hope that some of the students were inspired to pursue projects of their own.

However, my project is not yet finished. A few weeks before EOH, the Arduino was running out of RAM (I think), so I ended up having to remove all but the most essential parts of the code to get it working. I will work on reducing memory usage so I can re-implement the entirety of the calculator communication protocol. Besides that, I still need to repaint the enclosure once the weather warms up. Also, I will eventually need to write a proper control program on the calculator that looks and works better than my demo software.

Below are some images from my exhibit. The PowerPoint I displayed is available here.

Edit: Fixed Dropbox link.

Exceptionally cool, ajcord! I'm sorry that I wasn't closer to check out your demonstration in person. As always, we are here to help as you try to consolidate the code. I would caution re-implementing things with wild abandon if there might be other less strenuous ways to shrink the code, but you're the PM. Good luck.

Another lapse in updates finds the project nearly finished and featured on Hackaday. I've filmed a couple of videos about the project (see the project page), and I'm going to film one of it actually running the lights in a theater tomorrow.

But I've hit a snag. For some reason, my USB initialization code that turns on the voltage pump doesn't want to work anymore. I haven't changed that part of the code since I wrote and tested it successfully, so I'm not sure why it would suddenly stop working. Does anyone have any ideas?

The relevant code I'm using is as follows. It's actually written in hex opcodes in an Axe include file; below is the translation.

Code:


Edit: I guess I should explain what debugging I've already done. I fired up Calcsys and tried setting the ports manually (44->54, C4->54, 08->4C, 01->8F). When I did so, everything looked good until I tried setting $8F to 01. It would hold the value $0D for a fraction of a second before returning to $08. I've also tried variations such as not setting $54 to $44 first, without success.
Then I came across this topic and tried Kerm's suggestion of using the Linky initialization code. I tried stepping through the code and manually changing the port values, but no luck.

Edit 2: I checked the battery level reported by TI-OS, and it said 4 (which is the highest). Nonetheless, I tried changing the batteries, and suddenly the USB power worked again. I put the older batteries back in, and the USB was powered for a second or two before turning off. This occurred several times. Based on these observations, it seems that my older batteries are exactly at the minimum voltage required for the pump. I would measure that voltage for future reference, but unfortunately I don't have a meter. I might be able to check them tomorrow at work.

Wait, control DMX channels with a calc? Ok, that is epic!

Thanks, Sorunome!

Here's my latest video of it actually controlling the lights in a theater:

I ran into this same issue with my GPS project. The batteries have to be just around 6V for the USB port to be able to pump out 5V; otherwise it doesn't work. It's quite frustrating, especially since I know it's stepping the voltage down and then up again, and if it skipped that part (and used something like a Zener diode with a resistor, which is also admittedly wasteful) the voltage would be more than sufficient down to 5V.

If only we could go back in time and tell the engineer that designed it

Is there a similar issue with the TI-84+C's rechargeable battery?