RGB to HDMI using a Pi Zero and a small CPLD

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danielj
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by danielj » Mon Aug 05, 2019 6:52 am

I think I might have a couple knocking around. This is strictly DIY though, you'll have to source parts and build yourself. Let me know if you want one and I'll have a look and see what I have :)

d.

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tricky
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by tricky » Mon Aug 05, 2019 7:53 am

Did anyone look into getting them prebuilt?
I'm not sure I would be asking for the right thing.

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Elminster
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by Elminster » Mon Aug 05, 2019 8:22 am

I think I am with Dave's post above. The hardest bit of RGBHDMI is the cable. Building two cable at the moment and the flipping wires keep breaking as I put them into the Molex connectors. Possibly dodgy CCTV wire, or maybe Molex crimp tool is putting to much pressure on.

With Hindsight I would do what Ian did and solder directly onto board.
Last edited by Elminster on Mon Aug 05, 2019 8:23 am, edited 1 time in total.

cmorley
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by cmorley » Mon Aug 05, 2019 8:36 am

tricky wrote:
Mon Aug 05, 2019 7:53 am
Did anyone look into getting them prebuilt?
I'm not sure I would be asking for the right thing.
I was going to, hence the brief discussion I had with hoglet about using a cheaper CPLD. If you assemble your own the £1 or £4 for a CPLD doesn't make much of a difference but when you are assembling and selling that extra £3 x2.5 would add £7.50 to the price for that one part. Retail sub £20 would be nice... if they are £30-40 assembled (+ Pi on top) then I think that is too much.

The reengineering would take time and effort which is probably not worth it. Max V for example are cheap but they are FPGA (LUT + registers) not CPLD (product terms + registers) so development and testing would be required too. So I shelved the idea of me doing it.

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BigEd
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by BigEd » Mon Aug 05, 2019 10:23 am

I'm not volunteering to do the production, but I'd guess that even at £50 they'd sell really well - it's such a great picture and such a neat solution!

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danielj
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by danielj » Mon Aug 05, 2019 10:32 am

Once I've finished with these MIDI thingies I might have a look at doing a limited run of these... But I'm not committing to it, and certainly not committing to any timescales!

d.
Last edited by danielj on Mon Aug 05, 2019 10:32 am, edited 1 time in total.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by Muddyfunster » Mon Aug 05, 2019 6:38 pm

I'd be very interested even at £50. =P~

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Elminster
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by Elminster » Sun Aug 11, 2019 8:11 pm

IanB wrote:
Fri May 17, 2019 2:56 pm


Here is a drilling template pdf from kicad:
Drilling template.pdf


Print and cut it out, push pinholes through the centre points and place face down on the inside of the case. It should just fit in the narrow direction with little or no slack but you will have to centre it in the long direction. The holes should be closest to the side with the hdmi and usb connectors and you should push the template towards that side if there is any slack as the board is mounted slightly off centre in the narrow direction. (You have to make pinholes because the printing is face down on the inside of the case.) As the cases are so cheap, it's worth getting an extra one in case of drilling mistakes.
Worked a treat. 3 RGBHDMIs all boxed up now, and only a little filing the holes. My also has extra cut out at the sides as I didnt solder cable to the board.

One RGBHDMI board (the one hooked to the Electron) has the no programmer mod done, as above. The Master is going via the scart to HDMI convertor as it has videonula. I have one for when I get one of my boxed machines down, and a spare. No more unplugging cables from machines and monitor. Well less anyway.

Tick this off the todo list.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Fri Oct 18, 2019 9:42 pm

Well I finally learned how to use Kicad and this is my first attempt at a 6 bit version of the PCB using a 5x2 IDC connector.

rgb-to-hdmi.jpg

The signals on the header are 2 bits each for RGB, Sync, Vsync, +5v & 0v. All 8 inputs are now pulled low by resistor packs so there will be no floating inputs if only some of the signals are used and I changed the LEDs to through hole so they can stick through the case

I also added the in system programming connections which are wired using pre-linked solder pads (JP1-4) so they can be cut and a JTAG connector added in case of a bricked system.

I had to remove the 74LS08 buffer although it wasn't needed on my unbuffered electron anyway. I also had to remove the debug header but it's possible that can be added back in by the reset switch. (A header can be soldered onto pins 6, 8 & 10 in any case if needed)

Using the IDC header means that PC style cables for MDA / CGA / EGA can be made using IDC ribbon cables and even BBC style cables can be made with IDC at one end.

One possible future option would be to make adapter PCBs for other source types that could be plugged into the 5x2 header. (e.g. my monochrome adapter level slicer or an electron buffer if needed)
Last edited by IanB on Fri Oct 18, 2019 9:47 pm, edited 1 time in total.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by -B- » Fri Oct 18, 2019 9:46 pm

Nice work =D>
Atom | BBC Model A | BBC Model B | Electron | Olivetti PC128S.

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