Got some text rendering working from forth on CFM.
I wanted to be able to show a full 64 column traditional Forth screen on the display, but at only 320 pixels wide, that means 5 pixels per character horizontally, which is not a lot. So I've drawn a halfway readable tiny font.
The PicoCalc is an ILI94xx series LCD controller, a chip I know well. With some care you can get vertical text for free.
Okay, this is decent. I have a habit of doing "high-waisted" capital forms to match high x-height, which gives the face a bit of a Charles Rennie Mackintosh vibe, but I feel like the 8 needs opened more to distinguish it from the 0.
This is a 16 bit color display, so there's no reason the default palette can't be Catppuccin. 😻
(Edit: goddamn I _always_ get Mackintosh's first name wrong by cross-wiring him with John Rennie of cast-iron fame.)
This board's running CFM1 at 40MHz, and repainting the display text is significantly faster than most of the demos running on the 150 MHz RP2xxx board that came with it. (I read over the code people are using, and it misses a lot of optimization opportunities.)
Theoretical minimum time required to repaint the full display: 81 ms.
My mostly-unoptimized prototype routine (some of which is being displayed on the screen there) is taking: 85 ms.
Alright, I figured out some of the reasons why my display repaints are faster than others'. (Not everyone's -- there are some very fast demos on YouTube, source unavailable.)
A meme appears to have spread that the ILI9488 doesn't support 16-bit color mode in 4-wire SPI mode, only 24-bit. So these applications are sending 50% more bits than I am.
The meme seems to stem from an error in a diagram in the datasheet, but the datasheet _text_ says it's supported, and it's what I've always used.
I wonder if I should send some PRs to people.
Awwww yeeeeah smooth scrolling
(The ILI9xxx parts can be programmed to display with an offset in vram, poke that carefully from a loop and you get this! This was a single line of code change because Forth.)
@cliffle omg this is so sick aaaaaaa
@cliffle i have spent my entire weekend contemplating the idea of getting a picocalc. thank you for posting abt yours <3
@scrabsha I will warn you, the keyboard was created as a torture device.
But otherwise it's a fun piece of kit.
@cliffle goes to show again how important accurate docs are. A whole class of people now think this chip is worse than it is.
How many chip sales have they squandered? We'll never know, but it's possible it's a lot
@diondokter Maybe -- this chip is quite common in low-cost TFT panels, and I think a lot of people see "24 bit color" as a feature. I'm only forcing 16 bit color because I'm a giant performance nerd, and because of its maximum 20 MHz SPI rate.
@cliffle ohh, very nice
@linear I'm glad somebody is getting value out of this 😅