Project Logs

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• No gods. No masters. No frame buffers. No external libraries.

  Benchoff • 05/23/2020 at 19:31 • 1 comment

  A terminal requires a 'new line' command. Therefore, I need some way to move all the characters up one line. The conventional way to do this is to keep a circular array of all the characters on the screen, and whenever a new line character is sent (or pressed), I would redraw the entire screen.

  No, wait, scratch that. The conventional way to do this is by selecting a display with a hardware scrolling function.

  Alternatively, I could keep the entire display in a frame buffer and write it out constantly, shifting up one character line whenever there's a new line command.

  The math: Keeping the contents of the display in memory as characters requires at least 1840 bytes (80 characters by 23 lines, because we don't really care about the top line of characters.) Keeping the entire display in memory as a bitmap requires at least 48000 bytes (800x480 at 1bpp, with some bitstuffing). Both of these options are onerous, so here's a way to scroll an entire display in 58 bytes.
  

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• Font Rendering Speed++

  Benchoff • 04/29/2020 at 16:45 • 1 comment

  On the advice of someone who's actually helpful on Twitter I've spent the last few days finishing the font set (ASCII Extended code page 437, the old DOS extended ASCII with those weird 'box' characters), and optimizing the font rendering speed. First, the results:

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• You can make a baby and a bitmap in nine months

  Benchoff • 10/16/2019 at 17:42 • 3 comments

  The last update for this project was a realization that a 'dumb' display would cost too much; the driver chip was too expensive, and if I didn't want to go with a driver chip, the microcontroller would be too expensive. The solution to this problem was to use a display with built-in graphics RAM, in this case a display with the NT35510 controller chip. There's a problem with this solution - no one has a driver for this display, or at least one that is portable to other (read: modern) microcontrollers.

  ...Which means I need to write a TFT driver. This took nine months. Here's the result:

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• Unit Cost And Economics

  Benchoff • 05/01/2019 at 04:12 • 3 comments

  Right now, I have the schematic and design done enough that I can get some quotes and go through the actual cost engineering of the VT-69. The TL;DR, is that this would cost more than you would pay.

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• System Design, Previous Work

  Benchoff • 04/18/2019 at 17:21 • 0 comments

  The core feature of the Dumb Badge is to provide an 80x24 character display, with a keyboard, and a serial port. The first requirement of a high-resolution display is the hardest requirement, but there are many cell phone screens that will give you 800x480 pixel resolution, conveniently the same width as the display in a DEC VT100. The display is therefore the hardest part of this project, and demands specific engineering decisions. The purpose of this project log is to discuss these engineering decisions, while covering earlier work done by others.

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• A Design Study

  Benchoff • 03/14/2019 at 20:48 • 2 comments

  I am designing the Dumb Badge with the idea that is a product, not a single one-off project. Being a product demands some work must go into the design, both the design language of the enclosure, but also the typefaces and logotype of the screenprinting and packaging. Basically, I need to decide on a font or two. It's also time to start designing the enclosure, which means I need to imagine what a product made in the alternative history of 1991 would look like.

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• The Prototype Keyboard

  Benchoff • 03/02/2019 at 20:05 • 0 comments

  I'm buying a thousand silicone keyboards, months before I have finalized hardware. I need a way to test the samples of these keyboards, and the easiest way is to turn them into a USB keyboard.

  The TL;DR is that everything is on the Gits

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• On the subject of keyboards

  Benchoff • 02/10/2019 at 18:51 • 3 comments

  The dumb badge requires a keyboard, and I'm doing this with a silicone keyboard like you'd find in a remote control or a ZX Spectrum. That's the easiest and cheapest way to put 100 buttons on something. But what is the layout going to look like? It's time for a review of existing terminal keyboards, how I made my keyboard, and a neat testing apparatus.

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