Early proto proof of concept (using Ben Nanonote) looks promising. Surprised at apparent readability of the tiny (Type).
Eventually, a nice(!) UI grace note would be to pop up a larger overlay of the character the jog wheel is currently pointing at. For people with non-20-something eyes and sub-optimal vision that will improve usability approx. one gazillion percent. Thanks for posting these Anelok progress reports! Ron K Jeffries --- Ron K. Jeffries 805-567-4670 On Sat, Sep 21, 2013 at 8:22 AM, Werner Almesberger <[email protected]>wrote: > I put together a simple test board for display and wheel. It's called > "DUI", not for Developing Under the Influence but for "Development > board, User Interface". > > Schematics: > http://downloads.qi-hardware.com/people/werner/anelok/tmp/dui.pdf > > Files live here: > https://gitorious.org/anelok/anelok/source/dui > > The board connects via a short cable and UBB to a Ben. The Ben > provides power and all control. The board only has the display, the > capacitors and resistors required for operating the display, the jog > wheel, and a few diodes for multiplexing display and wheel. There is > no MCU, RF, or any of the other complicated stuff. > > This is what the electronics look like: > http://downloads.qi-hardware.com/people/werner/anelok/tmp/dui-wheel.jpg > > The board has the size I'm currently aiming for for the final > device. (Note that this is likely to change. I've already grown it > by a few mm over the last days, to better accommodate the display.) > > First impressions of the assembly: > > - the display's FPC ("Flexible Printed Circuit", colloquially > "Flexible Plastic Cable"), while small, was very easy to solder > > - the data sheet doesn't make it clear, but the contacts are plated > on both sides and seem to be connected (didn't test that). This > means that one could also run the FPC under the PCB or (in a > larger device) run the cable flat, without bending. > > - that critter is tiny ! It's basically two thin glass plates with a > film of magic in between. I was afraid of breaking it, especially > when bringing adhesives into the game, but despite its delicate > appearance it has resisted all my efforts at destruction so far. > > - when checking the current setting resistors (R1 and R2, together > 760 kOhm), I found that they read far too low. I first suspected > that I may have picked the wrong components. But it was probably > just the flux. I've seen flux form conductive paths of some 100 > kOhms in the past, e.g., keeping chips in reset for a short > while (long enough to make the other chip that depends on it fail > to come up, yet short enough to destroy all evidence by the time > one starts to measure), so this is something to take into account > when building this sort of circuit. > > - the wheel didn't pose any undue problems > > Then I wrote a little test program on the Ben (using libubb) and > brought up the display. > > The only problem there was that the Ben reset when turning on power > on the card slot. This is something that happens quite often when > connecting anything but a memory card. I did allow for a generous > "charge period" (driving all the data pins high to pre-charge any > caps through the pull-ups and only then turn on power), but this > wasn't enough in this case. > > Not sure why the pre-charging trick didn't work this time. The board > has only about 11 uF in total and most of that is switched off on > reset. Fortunately, turning on uSD power on the Ben with the DUI > board present and then hot-inserting it did the trick. > > The rest of the bringup went smoothly. I made my program display an > X bitmap file: > > http://downloads.qi-hardware.com/people/werner/anelok/tmp/dui-hello.jpg > > This picture was taken at regular lab hours, i.e., at night. > Readability is as good as one could hope for. Today's weather is > cloudy and the forecast says it'll stay that way for the next few > days. So I won't have a good daylight test for a while. > > Contrast stays constant at any angle, very e-paperish and unlike > LCDs. The display does reflect bright light. > > I then added Ron's nightmare, some tiny text (5x3 pixels) about 1.1 > mm (3.3 pt) in height: > > http://downloads.qi-hardware.com/people/werner/anelok/tmp/dui-arrow.jpg > > Even that is barely readable. I then wrote a bit of code that reads > the wheel and tries to make sense of its inputs. That code is very > primitive (e.g., no debouncing) and it sometimes gets the direction > wrong, but it's good enough for demonstrating the concept: > > http://downloads.qi-hardware.com/people/werner/anelok/tmp/anelok-dui.ogv > > Xiangfu has uploaded the video to YouTube. I can't get it to load, > but this is where it should be: > > http://www.youtube.com/watch?v=BYlb4---BU8 > > Don't read too much into what's happening there. That's not a real > GUI. All the program knows is how to display a bitmap and to draw a > little triangle. It has no concept of characters, fonts, etc. > > Conclusions: > > - I like the display. Works without a fuss and performs well. > > - the wheel also seems to be fine. Debouncing needs some looking > into. Since one can't grip the board very well with a Ben > dangling off it, it's hard to tell whether the wheel will "feel > right", but I'm optimistic about that. > > - the PCB (0.8 mm) doesn't flex too much, even without a case > supporting it. > > - the wheel may be a bit too close to the display. I'll probably > either move the display by a few mm to the left or enlarge the > board by a few mm to the right. Depends on how the layout goes. > > - I initially thought to have a some rigid structure for the spacer > between display and PCB but given the flimsy nature of the > display, I think just a bit of foam with a weak adhesive (the kind > you find on Post-it(r) notes) will do. > > - the display is susceptible to smudging and scratching. May need a > silicone seal when put into a case. > > Still not tested/checked: > > - power consumption, > > - voltage levels, especially the level of the high voltage (the OLED > has a DC-DC converter to generate ~12 V), > > - behaviour when turning on more than 50% of the pixels. This OLED > has the known issue of its DC-DC converter being too weak for > driving all the pixels at the same time. This shouldn't be a > problem for normal white-on-black use, but we'd still want to know > what happens when exceeding that limit. > > - shutdown behaviour. The controller data sheet describes bringing > down the rails one by one, but that doesn't seem to be a > requirement. Need to check whether anything odd happens if I just > do the proper software shutdown, assert reset, then cut all the > rails in parallel. I don't expect any issues with that. > > The next big item will be getting the MCU to work. > > - Werner > > _______________________________________________ > Qi Hardware Discussion List > Mail to list (members only): [email protected] > Subscribe or Unsubscribe: > http://lists.en.qi-hardware.com/mailman/listinfo/discussion >
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