[HN Gopher] Towards an HD44780-Based Video Mode ___________________________________________________________________ Towards an HD44780-Based Video Mode Author : ingve Score : 108 points Date : 2021-05-07 15:06 UTC (7 hours ago) (HTM) web link (github.com) (TXT) w3m dump (github.com) | phiiiillll wrote: | Reminds me of the 1024 color CGA hack | https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-... | notwedtm wrote: | Can someone explain this for us mere mortals? | smiley1437 wrote: | I think with this project you can control the display at the | pixel level instead of the character level, like this link in | the article: | | https://m.youtube.com/watch?v=nxFad7Rxw7Q | | However that demo is quite old (2013?) so I could be | misunderstanding something | st_goliath wrote: | Long ago, many devices that needed simple text output, like | super market checkout registers, had simple LCD modules in them | with e.g. 2 rows with 16 characters each. | | Those modules are just bricks with a display on them that you | can control using a parallel interface. Because of their | simplicity, they are/were also very popular with micro | controller hobbyists _long_ before Arduino was a thing. | | The HD44780 (and clones) are very widely used controllers on | those modules. They can be connected in 4 bit or 8 bit parallel | mode, you can send over characters that it should display | (using a built in raster font) or some special command | sequences for e.g. clear the display, set the cursor position, | ... kind of like a very simple terminal. | | The displays with 4 rows instead of 2 typically just had 2 of | those controllers in them that you needed to interface to. One | for the bottom 2 rows and one for the top. | | Some variants of the controller clones can load a custom font | lookup table. By breaking a graphical image up into blocks and | loading those into the font lookup table, you can use the | device as a very hacky graphics display. | | Alternatively, if you rely on semi-documented internals and get | the timing _just right_ , you can swap out the data while it is | drawing a character and splice your graphics together that way | using the built in font. This will also get you a more decent | refresh rate. Both variants are discussed here. | smiley1437 wrote: | Can I play Doom on it? | MegaDeKay wrote: | Doom is playable on MiSTer, so assuming this display can be | used as a generic output device, the answer is yes. | | https://twitter.com/misteraddons/status/1283620207978741761?... | varispeed wrote: | There is so many clones of these displays, sometimes it's hard to | get something working, especially to initialise the screen | consistently. I remember spending so many evenings getting | display to reset without having to disconnect power physically. | There is no documentation, or documentation is plainly wrong. If | you are lucky to get any example code from manufacturer, chances | are it will not work anyway. But I admit it was fun to "hack" | those. | baybal2 wrote: | Hitachi knew how to make chips. Times change | thanatos519 wrote: | I thought I remembered the name from the LCD display on my Apple | Network Server, which was supported under Linux and gave me a | mini 'top' on the front of the box... and... I think that was | enough, thanks. | transistor-man wrote: | This is wild. The HD44780 is so incredibly ubiquitous in | character displays, they are everywhere. Really curious to see | where this goes. | neilv wrote: | Nice! This is a million times cooler than my modest toying with | these useful little devices. | | I have a few of those displays, for a hobby server "front panel" | project. (3 CrystalFontz with buttons and USB, and an Adafruit | RGB-backlight one plus USB backpack.) I only got as far as using | the small set of software-defined characters to do a charts/bars: | | https://www.neilvandyke.org/lcdbling/lcdbling-20190121.jpg | | https://www.neilvandyke.org/lcdbling/lcdbling-horizontal-bar... | | I was planning to use one for my GPU server, and then another for | a self-contained simple admin console for a home network router | (no needing SSH/Web to do basic admin functions, nor needing to | find a sufficiently trustworthy separate device for that). | | You can get 5.25" drive bay mounts for some of the CrystalFontz | ones, including room for D-pad, OK, and Cancel buttons. And | besides their display and input features, some of them can hook | into ATX motherboards, and a perform watchdog function, to reboot | a frozen box. | | If you're buying CrystalFontz units that aren't factory-sealed, | beware that they might've had downstream firmware put on them | (that's how I got a FireEye one, and a Honeywell one, | accidentally). A CrystalFontz person told me that the stock | firmware can only be put on at the factory, but I haven't | verified this (and I do have a sealed unit from the factory now, | which I suppose might be cloned). | | (Oh, if you're playing with the Adafruit ones, IIRC, the one I | have seemed to be doing some kind of nonvolatile storage write | for each color change, at least the way I knew to change the | color. If that's the case, I don't know whether or how soon a | write cycle limit on that would be hit.) | epall wrote: | This is brilliant! Check out the demo video at | https://www.youtube.com/watch?v=nxFad7Rxw7Q | Narishma wrote: | That's an old demo from 2013. | dylan604 wrote: | I kinde of see that screen shaking it's head at the end of it | going "WTF just happend" like it's waking from some crazy dream | it just had. That's not what I'm supposed to be used for at | all!! Sort of like it was just given the choice of a red/blue | pill | zwog wrote: | Amazing. HD47780 displays are not only commercially ubiquitous, | they were used everywhere when casemodding was still a thing. But | so far, hardly anyone seems to have thought to exploit the | possibilities. | thudson wrote: | The WEH001602A is pin compatible to the HD44780, with OLED output | instead of LCD. In 8-bit parallel mode with an FPGA you can | exceed the recommended clock rate to drive quite a bit of data | into the displays: | https://twitter.com/qrs/status/1088240598971310081 | thudson wrote: | Similar higher-than-rated-bandwidth can be achieved on the | TRS-80 Model 100, which uses an array of 10 HD44102 | controllers. With an FPGA it is possible to draw full motion | video on the LCD: | https://twitter.com/qrs/status/1092410264316653568 ___________________________________________________________________ (page generated 2021-05-07 23:00 UTC)