PICO9918: A drop-in replacement for a TMS9918A (with source)

[visrealm]

Nice one, Cecil. Note: I will be keeping the firmware (source code) compatible between v0.3 and v0.4+. A couple of the GPIO pins have changed (necessarily) between v0.3 and v0.4, but it's nothing a compile-time flag doesn't fix.

I'm hoping to get my hands on a Colecovision soon. One of the very generous AtariAge members has offered to send me one (all the way from the US too). Looking forward to trying it out.

[visrealm]

cbmeeks wrote:

I just got my v3 boards. I will be ordering the SMD parts to finish them very soon then I will start testing in some TI's.

When you get around to building one, note there are a few 0 Ohm resistors (jumpers). I recommend omitting the one labelled RST. There's a note about it in the repo.

[visrealm]

PICO9918 v0.4 finally working.

Apologies in advance for the vertical video 

https://youtu.be/KSbJnAwclQw

Works great! Got the blinkenlights. Much lower profile than v0.3.

[BigEd]

Splendid!

As you note:

Quote:

It's a replacement graphics chip using new parts with VGA output. It can fix computers with bad graphics chips, bad vram, bad video crystal, etc. All that stuff is on board. You can also enhance it with additional graphics modes, etc. It already supports an 80 column text mode the original doesn't.

[cbmeeks]

This is excellent!

I just got my parts from Mouser yesterday to build v3. I ran out of solder paste so I have some coming Tuesday.
I might just try and hand solder one this weekend. Soldering 0603 is hard by hand but I've done it before.

[cbmeeks]

Well, I have to accept defeat. I was not able to hand solder those resistor networks.
I will have to wait for the solder paste to get here Tuesday. Now I wished I would have ordered the template when I ordered the boards. lol

[visrealm]

They would be tricky to hand solder. I ordered the stencil. The v0.4 boards were next level again with 0402s and all leadless ICs. It took me quite a while even with a stencil and hot plate.

In other news, another AtariAge member ordered some v0.3 boards and tested on his Colecovision:

https://forums.atariage.com/topic/36765 ... nt=5501952

Was great to see it running on something else and have someone else validate the design.

[Rob Finch]

Great project. I have just been reviewing some of the source. Any possibility of an HDMI version?

[visrealm]

Rob Finch wrote:

Any possibility of an HDMI version?

You mean DVI? #nothdmi

Potentially, I know it's possible. Haven't looked into it yet though.

[Rob Finch]

HDMI and DVI are similar; they are both digital standards, but I believe HDMI encodes things into fewer signals. I was looking at some of the beefier embedded SBCs that support HDMI output. However, supporting additional features increases the power consumption. HDMI requires only eight signals, no DAC, so it is a little more compact than VGA. I do not think it is possible to bit-bang HDMI at the required frequencies, but I do not know.

[visrealm]

You can send DVI signal over HDMI. The reason for calling it DVI is HDMI requires a license fee. So, we don't support HDMI, it's DVI.

[drogon]

visrealm wrote:

You can send DVI signal over HDMI. The reason for calling it DVI is HDMI requires a license fee. So, we don't support HDMI, it's DVI.

There is a little more to it than that - HDMI does require a license to use which is not easy to get at the hobby level. (< 10,000 units PA is in the region of $5K PA plus a variable amount of royalty per unit - 15c-24c depending on options)

HDMI can also carry audio - 32 channels and high definition audio too, DVI can't. The bit-rate of HDMI is up to 4x faster than DVI - so for "4K" video you need HDMI. However connecting a DVI output to HDMI input is possible and sometimes the reverse too - if the resolution is low enough (usually just up to standard HD; 1080p) I use adapters to connect Raspberry Pis HDMI output to an older 1080p monitor I have which only has VGA and DVI inputs.

Stick to DVI and use an adapter.

-Gordon

[cbmeeks]

Which is exactly why HDMI needs to be abandoned and the market needs to move to an open standard. Which is really shocking if you think about it. Just about every major player in the digital world (MS, Sony, Apple, etc.) have to pay that (I think German) company royalties for HDMI. Seems like the TV companies and the other companies should get together and create an open standard. They can phase out HDMI.

Of course, HDMI is so saturated that it will be difficult to do that. That's why you can still buy TV's with composite and S-Video.

But still, none of those old formats need royalties.

Another aspect, IIRC, is that HDMI also has the ability to do DRM.

[drogon]

cbmeeks wrote:

Which is exactly why HDMI needs to be abandoned and the market needs to move to an open standard. Which is really shocking if you think about it. Just about every major player in the digital world (MS, Sony, Apple, etc.) have to pay that (I think German) company royalties for HDMI. Seems like the TV companies and the other companies should get together and create an open standard. They can phase out HDMI.

Of course, HDMI is so saturated that it will be difficult to do that. That's why you can still buy TV's with composite and S-Video.

But still, none of those old formats need royalties.

Another aspect, IIRC, is that HDMI also has the ability to do DRM.

While I think you're right I also see issues. One is the XKCD Standards argument (See: https://xkcd.com/927/ ) and the other would suggest that without an official standard and proof you adhere to the standard so you can legally display the logo then you'll end up with all sorts of incompatibilities. (Same for USB, DVD, CD and so on)

For a large maker of video stuff (say Raspberry Pi) the additional cost is not that big a deal once units started to ship. Dell tried to get round it by inventing their own standard - (Dell DisplayPort) which was great when you have a Dell PC and a Dell monitor, but when you have a Dell PC and a generic nice high-end non-Dell monitor (which is what my home desktop setup is) then it presents issues. (I had to buy an adapter - did I mention incompatibilities earlier?)

And even, AIUI, Dell have had issues with various legal threats and so on.

Sadly, there is no easy solution for the home/hobby user. Virtually all monitors you can buy these days have HDMI. Those with DVI are on the decline and those with other analog formats e.g. VGA, S-Video, SCART, Composite, (Gasp!) UHF are really on the way out.

Generating VGA from a microcontroller isn't hard though - but it uses up many GPIO pins depending on your bits per pixel colour (R, 2R network unless you have a high speed DAC+CLUT) plus 2 for the syncs. DVI (and single lane HDMI) isn't too bad but you need a high speed serialiser from your RAM to the cable (Which the Pi Pico can do) I have an FPGA thing that has a micro HDMI socket and some magic to drive it, but who pays the royalties? I've no idea.

I don't think there is an easy solution for us retro hobbyists and I don't think there ever will be.

-Gordon

[cbmeeks]

Yeah, there have been a few failed attempts at replacing HDMI. Which is why I still find it surprising. Like Bil Herd once said, "pennies count in quantities of a million".

All of the BIG companies have to pay that royalty. This wasn't always the case. Same thing with OGG vs. MP3.

As for us hobbyist, our best bet is to stick with VGA/DVI. Fortunately, finding modern displays with VGA and/or DVI is still plentiful.