Apple II video to HDMI using Raspberry Pi Zero / Pico

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Apple II video to HDMI using Raspberry Pi Zero / Pico

Hi All,I'm finally making some progress on a simple Apple II to HDMI adapter using Raspberry Pis.https://lukazi.blogspot.com/2022/02/apple-ii-video-to-hdmi-using-raspberry.htmlCheers,Alex.

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Awesome

Very cool

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Great write up and progress!

Great write up and progress! I am currently looking for a "cheap" and small CRT but they are getting more difficult to find. My HDMI TV has Video In but won't display video from the Apple II. This looks very promising.

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Very nice work, as always,

Very nice work, as always, Alex! I'll be very interested to see the results of this project.

- Alex

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Great project!

This is a great project and I can't wait for it to be finished and ready to use.

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A2VGA - Pico IIe

Sorry, but I haven't had much hobby time of late. It is plodding along very slowly. An update here: https://lukazi.blogspot.com/2023/05/a2vga-pico-iie-card.html.

 

Cheers,

Alex.

CVT
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lukazi wrote:Sorry, but I
lukazi wrote:

Sorry, but I haven't had much hobby time of late. It is plodding along very slowly. An update here: https://lukazi.blogspot.com/2023/05/a2vga-pico-iie-card.html.

 

Cheers,

Alex.

 

Hi Alex,

 

Is this one related/based on the https://github.com/markadev/AppleII-VGA/ or the https://github.com/V2RetroComputing/analog?

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CVT wrote:Hi Alex, Is this
CVT wrote:

Hi Alex,

 

Is this one related/based on the https://github.com/markadev/AppleII-VGA/ or the https://github.com/V2RetroComputing/analog?

 

No the projects are not related to each other. They both output an Apple II picture within a VGA window and both use a Pi Pico to do the work however they souce the Apple II video data in completely different ways.  The AppleII-VGA / ∀2 Analog cards operate in the 50pin Apple II slots. They duplicate the Apple II video buffer by reading the Apple II bus signals. The A2VGA cards on the other hand generate their output by reading the raw Apple II bitstream data that is only available from specific pins ie located in the Apple IIe 60pin auxiliary slot and the Apple IIc 15pin video port. The A2VGA is based on my previous work from "A2 Video Streamer", "A2 Serial Video to HDMI Converter - Using the Beagleboard Black" and "Apple II video to HDMI using a Raspberry Pi Zero / Pico".  The projects do not share any code. The A2VGA's VGA generation code is based on the Raspberry Pi Pico SDK examples where as the VGA generation code for The AppleII-VGA / ∀2 Analog looks to be custom written.

I think that the AppleII-VGA and ∀2 Analog are awesome projects. I'm looking forward to seeing where these projects are taken. 

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Nice, I actually have started

Nice, I actually have started assembling prototypes of my own IIc VGA adapter.  One thing to be aware of is the IIc RGB adapter from Video-7, and it's signalling of color/monochrome. I originally was only going to implement the minimum to do text / gr switching between color and mono, but then found out the Video-7 adapter uses a couple of the soft switches to set a register in their adapter so you can get 560x192 mono graphics on the IIc under software control (for things like A2Desktop).

 

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Request for Documentation
GrizzlyAdams wrote:

Nice, I actually have started assembling prototypes of my own IIc VGA adapter.  One thing to be aware of is the IIc RGB adapter from Video-7, and it's signalling of color/monochrome. I originally was only going to implement the minimum to do text / gr switching between color and mono, but then found out the Video-7 adapter uses a couple of the soft switches to set a register in their

Very nice. Is there any documentation around (schematics/signal diagrams) as to how these IIc video adapters (Video-7 / Cable Le Chat Mauve) worked to achieve the different effects (560 mono mode / mixed colour mode) ? I've had a look around and I can find lots of information in terms of the colour modes and the Apple II memory but I can't find info on the signal operations.

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Handling different video hardware ie Video-7/Cable Le Chat Mauve

I've done some more research. 

 

The effect of having the combined Colour and Monochrome picture as shown in the Extasie slideshow (via the Cable Le Chat Mauve hardware) can be implemented by using the IIc's Video Port "VIDD7" signal. I'll use the elephant picture as the example here. Looking at the signal timing diagrams in documents such as Jim Sather's "Understanding the Apple IIe" does not help here because they don't give you a good representation of how those signals look over the entire video frame. Instead what I did on my video card was to switch the SEROUT signal with the other available digital signals, one at a time, to get the full screen visual representation. The folowing picture shows what you get when you look at the VIDD7 signal (at the elephant picture in the slideshow). This is exactly was I was hoping to find. Similar to the GR signal where you want to perform the colour killer operation one line at a time, using the VIDD7 signal you want to buffer the screen frame and perform the colour killer mask. With the black areas you leave the colour as is but in the white area you perform the colour killer operation. There are plenty of resources left on the Pi Pico to implement this.

 

VIDD7 mask.

 

The elephant on the left shows what the picture looks like where the whole sceen is set to colour mode. The elephant on the right is displaying the pciture as it was intended to be viewed (AppleWin Emulator - only when the video mode is set to "Color (RGB Card/Monitor)"). 

 

The left screen shot shows A2Desktop with the whole screen set to colour mode. The right screen shot shows the A2Desktop with the full screen colour killer applied.

 

In summary, even though I can see that the combined Colour and Monochrome mode can be easily implemented, I'm wondering if the effort of implementing it is worth it. With only a few disk examples that use this mode, you can see the results by opening up the disks in the AppleWin emulator or watch the result on youtube. I can't see a reason why a user would leave their video card running in this mode because it is going to incorrectly display a good proportion of every other Apple II software. I'll probably just have the VIDD7 signal connected in hardware and leave it to the user to implement this mode if they want it. 

 

From what I can work out A2Desktop uses this combined Colour and Monochrome mode (with the monochrome mask applied to the entire screen) to automatically tell the hardware to display monchrome in the main A2Desktop window. However this only works if specific hardware is used eg RGB card. I don't understand why they didn't do the same with the main A2Desktop windows as with the A2Desktop startup screen (the one that reads "Loading Apple II Desktop..."). That is displayed in monochrome on any hardware (not just special hardware) because it uses the GR signal. Maybe this is just a PAL motherboard thing and does not work with NTSC ones. I'm planning on just having one button to switch between the modes ie as seen in A2Desktop screen shots above.

 

I've looked at the IIc video port power supply, I've looked at the resistor values to impedance match the VGA cable,  I've yet to try to move the pixel clock rate from 24MHz (Pi Pico SDK) to something closer to the correct specification ie 25.175MHz. I'm trying to cememt which video port signals are going to be used (Needed: 14M, SEROUT, WNDW. Extra yes: GR. Extra undecided: SYNC, VIDD7, LDPS). 

 

I'm happy to hear from anyone else who wants a specific video signal included otherwise I'm going to finalise the current board revision. Thanks.

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Regarding A2D...

A2D maintainer here.  

The "Loading" screen is text, so mono.  

Other than the Video-7/AppleColor RGB/Le Chat Mauve Feline and the alternate Le Chat Mauve Eve, and the IIgs color control bits for composite and RGB, or esoteric approaches like VBL and cycle timed mode-switches, you're stuck with hardware. 

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Maybe a jumper?

And re: "who would want this?"

 

Well, me for one. I have Video-7 adapters (IIe and IIc) but not the right adapter path to drive a VGA or other monitor to actually use the software-controlled mode switch. And I'd like to see it with real hardware!  

I agree it's not for everyone and there are some software titles that accidentally trigger the mode switch because the hardware was so rare back in the day. But I'd still like a way to experience it. So, maybe a hardware jumper to opt-in to the color/mono switching behavior?

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Feedback

Thank-you for the feedback. I'll see what I can do. If it affects the performance of the other video modes then I may just release a separate firmware build otherwise I'll see about including it as another toggle mode.

 

 I'm using trial and error in an attempt to work this stuff out which is not ideal. I'm concerned that the colour/mono mode uses not only the VIDD7 signal but a combination of signals. I use Airheart to do a lot of the DHGR testing and from my calculations if this game is running in colour/mono mode then it will only display in mono. If someone has these rare hardware adapters and could do some testing for me (on which software titles are affected and which ones are not) preferrably on the IIc then please PM me. Thanks.

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