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Forum Index : Microcontroller and PC projects : PicoMiteVGA Design #2 Colour Mode Header
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| JohnS Guru  Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
What is the (Design #2) Colour Mode Header for, or more specifically what settings make sense and what would the default (not fitted / disconnected) do? John |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Well, it won't do any harm either way round. :) I've not got one of those, but I think you can just leave it in the Colour position. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5089 |
First firmware versions, you needed different connections to the vga connector depending you wanted lo res color, or hi res monochrome, the monochrome could be amber, green... just to get the retro feeling. Modern picomite versions do work with the same hardware for both modes. Edited 2023-02-19 06:16 by Volhout PicomiteVGA PETSCII ROBOTS |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Thanks. John |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Sorry to come back to this... I think the schematic means (with the current firmware) that I ought to be connecting GP19 somewhere. Is it to connect contacts 1 & 2 of the Colour Mode Header? Currently I look to have 8 colours, not 16. The Schematic: VGAMite - Project.pdf John |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2640 |
For 16 colours GP19 goes to VGA socket pin 2 via 820R as shown on p6 of the latest VGA manual. GP20 also goes to VGA pin 2 via 390R. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
That looks to be for Design #1 but I'm on #2. I think I _do_ need to connect in a similar way, though, thanks. John |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 375 |
@John. Had a look at your Schematic. Why is the Pico pin layout different from what we see on the pico modules? -modules have pin order 1 2 3 ....18 19 20 40 39 38 ....23 22 21 -in your schematic 1 2 3 ....18 19 20 21 22 23 ....38 39 40 Just wanted to point it out, it would be a pity to have everything ready and the module socket wrong connected  /Pluto |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
I don't know, but it's matherp's schematic (thus the Design #2 mention). Hopefully someone will have ideas! John Edited 2023-02-21 18:41 by JohnS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
If that's the correct schematic, John, and I assume it is, then the link should be on 1-2. That connects the VGA as follows: GP18 - Blue - VGA pin 3 via R12 GP19 - GreenLow - VGA pin 2 via resistor network GP20 - GreenHigh - VGA pin 2 via R14 GP21 - Red - VGA pin 1 via R13 VR1 sets the overall Green level and usually does very little (it depends on the monitor). Set it to max (2-3) initially and you may not need to move it. You can try leaving it off completely if you wish. If the header is linked 2-3 then GP19 output is ignored and all the Green signal comes from GP20. You will then get 8 colours from GP18, GP20 and GP21, which is better for getting 8 shades of grey on a mono monitor. The pin numbering on the diagram is how this PCB software works, I think. You can't have a 1-row connector with pins numbered 21-40 and the pin numbers on a 2-row connector appear to do one side then the other in the same direction. Only the text labels mean anything. Not a particularly simple circuit to lay out if you want to show bused connections. Edited 2023-02-21 18:54 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Pluto Guru Joined: 09/06/2017 Location: FinlandPosts: 375 |
https://www.thebackshed.com/forum/ViewTopic.php?TID=14417&P=1#179601 I can now see that this connector has been discussed before. Connections are OK, but a bit confusing when the socket and pico-module pin numbering are differing. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
The "normal" pin numbering for a 2-row connector starts at the arrowed pin as 1 then goes to the other row as 2 then back to the first row as 3 etc. This allows connectors of any length without messing up the numbering. Three-row connectors go 1-2-3 across the three rows then 4-5-6 on the next pins along etc. Starting the second row from half way through the count isn't sensible at all. Connector wiring has nothing whatsoever to do with DIL socket wiring. Not unless you deliberately try to make it so anyway, in which case the numbers on the connector pins are wrong. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Thanks. Yes, I got the schematic from the files. (I couldn't create it!) I just trusted it, soldered up the connectors etc and (apart from the colour mode thing) it just worked :) Well, the white is rather pink but maybe that's the colour mode - just soldered on a header so will see. Or it's the trimpot? (But I've tried that, can try some more.) edit: much better now I have the header, and with its pins 1&2 shorted together John Edited 2023-02-21 20:34 by JohnS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
The best way to adjust VR1 is to display a block of white (use the BOX command) then see if it can be adjusted to get rid of any tint. It's not guaranteed because it depends on the colour rendering of your monitor. Some monitors have various colour settings that can be used and some will be better than others. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Thanks, John |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2640 |
The way I got pure white (the lazy way) was to reduce the values of all the resistors a little so there is a bit of overdrive on all 3 signals. The monitor clips them all to 100% giving pure white. The simple design #1 resistors can be fitted to the design #2 board, with a few wire links to bridge the gaps. Edited 2023-02-22 14:18 by phil99 |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Thanks! I would not have even thought to try that. edit: what sort of value resistors (roughly) please? John Edited 2023-02-22 19:24 by JohnS |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2640 |
On the breadboard version I had:- GP18 - 220R - VGA 3 B GP19 - 680R - VGA 2 GL GP20 - 330R - VGA 2 GH GP21 - 220R - VGA 1 R For my monitor that was a little more overdrive than needed. So now use the same values as on p 6 of the VGA manual and still get pure white. GP18 - 270R - VGA 3 GP19 - 820R - VGA 2 GP20 - 390R - VGA 2 GP21 - 270R - VGA 1 If those give you pink leave red at 270 and reduce the others. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 4044 |
Thanks, John |
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