The E-Ink Badge
Some notes about my E-Ink studies.<p>1. E-ink requires a number of external components, even with their "chip on glass". In particular, E-ink requires a high voltage to change and charge the ink. I've seen inductors on most of these reference designs (ie: suggesting a boost converters of some kind).<p>2. E-Ink is very slow especially at this price range. Static images are fine, but don't expect animations.<p>3. E-ink protocols take a "temperature". In my cases, I've just been hard coding it to 25C / Room temperature, but this suggests that low-temperatures or high-temperatures may change the behavior of the screen.<p>4. E-ink is very "bursty" with power, using more power than LCD when changing images, but then zero power for most of its life. Be sure to think carefully about the current associated with this burst, especially if you're using small CR2032 coin cells (which have ~10 to ~100 ohms of internal resistance). A ~100mA draw on the charge inductor isn't out of the question (at 10-ohms, that's a voltage drop of 1V, which probably browns-out the RP2040). A slow-start circuit could solve this but you'd need to consider the longer charge times. Another method is to have 2x CR2032 cells in parallel, which lowers IR (parallel resistors lower resitance). I'd be most interested in studying the power-network of this design, I bet there's some interesting things going on here.<p>5. Most E-ink screens seem to be some kind of SPI protocol (4 wire). This is very similar to mini-LCD screens.<p>---------<p>LCD screens use more power, but get you color, more resolution, animation and seem to be cheaper still. Furthermore, LCD requires fewer external components (maybe a charge-pump set of capacitors, but some LCD screens don't even need that). Note that color/resolution/animation all costs processor power / storage / RAM, so be careful what you wish for.<p>LCD might be more suitable for beginners. But e-ink is very cool and awesome.