RetroBSD

2.11BSD operating system for microcontrollers
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PostPosted: Sat Aug 30, 2014 10:55 pm 
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alexfru wrote:
The idea is viable, but without doing the math and without trying, I don't know if it's actually doable.
But that would only give me text, whereas I'd like to be able to draw graphics. Text only is not much fun.

In that case you will need to use something with external RAM, such as an SSD1963 (the chip used on the µVGA-III from 4D Systems, and also on most 7" TFT screens).

Incidentally, my TFT driver is running in text only, storing 80x40 characters in 7 bit, with the 8th bit indicating bold.

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PostPosted: Sun Aug 31, 2014 11:24 am 
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On-display memory would solve the problem, but require an extra part and some tinkering. I've done circuitry work a long time ago and have since switched almost entirely to software. Still have no iron, no wires, no miltimeter, no parts over here. I used to share all this with my dad back in Russia. But, oddly enough, even though I'm not doing it myself anymore, a newly made friend is actually trying to do this kind of work for the first time and I'm advising him how to do stuff and helping troubleshoot the breadboards and code. It's like you can't escape it! :)

It would be great if the Maximite author made a version based on the MZ. Just program the thing, no extra circuitry to solder or connect, just plug in the standard VGA display and voilà, pixels and colors! Minimum hardware making a great toy.

~3K for the text buffer is good. Do you have a blinking cursor? :)


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PostPosted: Sun Aug 31, 2014 3:19 pm 
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Alas not, no blinking cursor. I could easily enough if I were to incorporate a timer as well, but my CBA levels are maxed out with regards to that ;)

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PostPosted: Sun Aug 31, 2014 5:35 pm 
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Well, it turns out my CBA levels weren't actually that high, as I have now hooked a blink function into the CT0 interrupt to make the cursor blink every time time.tv_sec changes, so a 1 second on, 1 second off blink :)


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PostPosted: Mon Sep 01, 2014 5:36 am 
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Old-school block cursor, nice! :)


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PostPosted: Sun Sep 07, 2014 3:29 pm 
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Don't forget that you can compile emg to use the extra rows ;)

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PostPosted: Sun May 31, 2015 1:01 pm 
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Matt, I can't seem to figure out which model the screen chip is and which manual should be used. Your code says it's HX8357, and I can locate manuals for HX8357-B and HX8357-D00/D01. I'd like to avoid cross-referencing the code with the manual(s) and deciphering the model that way. The Picadillo board manual and schematics are suspiciously secretive. There's also other HX8357 code online, but for obvious and non-obvious reasons it looks different. So, which model is it? Is there a simple and correct answer? :)


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PostPosted: Sun May 31, 2015 3:05 pm 
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To be honest I really don't know. I doubt there's enough differences between the different versions to make any difference - the protocols remain pretty stable. In fact, they are suspiciously similar to the Ilitek chips.

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PostPosted: Mon Jun 01, 2015 10:01 pm 
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These two datasheets seem pretty close to what the hx8357 driver is doing:
http://www.adafruit.com/datasheets/HX8357-D_DS_April2012.pdf
http://www.displaytech-us.com/sites/default/files/driver-ic-data-sheet/Ilitek-ILI9341.pdf

HX8357-B looks different.


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PostPosted: Mon Jun 01, 2015 10:19 pm 
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Yeah, I think there may have been a certain amount of copying going on there :)

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PostPosted: Wed Jun 03, 2015 7:42 am 
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Matt, are you actually using your driver that's in RetroBSD? It looks like it's broken (cat somelongfile > /dev/tft0 stops pumping out chars to the screen after a few lines and hangs). Further, Serge and I want to modify it, either just extend while keeping the tty functionality or that and remove tty. The font is too small for many applications. IOW, it looks like the driver is currently more of a demo than a usable thing. Comments?


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PostPosted: Wed Jun 03, 2015 9:31 am 
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Yeah, that driver is far from perfect.

A better (certainly more useful) system would be a similar system to Linux, which has /dev/fb0 for the TFT interface as a framebuffer - basically giving direct access to the internal RAM of the TFT screen - and a "VT" driver which overlays on top of it to give a number of virtual TTY devices that display on it. Of course, that latter driver would be optional, so you don't have to have it compiled in if you don't want to use it...

The main issue with the current driver is it's a graphical device trying to do text, and the two don't really mesh - graphics devices don't scroll when the text hits the bottom of the screen, or certainly not easily... In a layered system the VT driver could (if there is enough RAM available) maintain a textual copy of the screen data and just refresh the screen from that building up the graphical information from a user-selected font file...

So yes, modify away :) Oh, and the DisplayCore driver for the Picadillo has read ability if that helps, though reading isn't wonderfully fast...

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