Search found 324 matches

by IanB
Sun Feb 17, 2019 1:42 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

hoglet wrote:
Sat Feb 16, 2019 8:02 am
Note, connecting a ZX81 does require some external circuitry:
This is the modified version of your Atom circuit to do the video to RGB/SYNC conversion:

composite2rgb.jpg
by IanB
Tue Feb 05, 2019 9:43 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

Sounds and looks great! It took me a tick or two to figure out what you're doing: the Beeb is putting out Mode 0, which is monochrome and sampled bit-exactly by the HDMI dongle, so the frame can be re-interpreted by the software in the Pi. Yes that's correct, I'm also outputting a line of data whic...
by IanB
Tue Feb 05, 2019 9:01 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

hoglet wrote:
Mon Feb 04, 2019 7:08 pm
That very interesting, and the results look excellent. Nice work Ian!
I've committed those changes and created a pull request so you can try it out

Here's a demo disk using some of the bitshifters NuLA pics:
hdmidemo.zip
(146.99 KiB) Downloaded 4 times
by IanB
Sun Feb 03, 2019 9:21 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I've got 16 colour mode 2 palettes working so the Pi can now produce equivalent picture quality to VideoNuLA but over HDMI: 16colourpalette-1.jpg 16colourpalette-2.jpg I was looking at the possibility of implementing NTSC artifact colours (or should that be colors? :) ) for use with PC CGA, Apple II...
by IanB
Sun Feb 03, 2019 2:32 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

Does the Y output just drive all three of the RGB inputs then? Yes Do you have any plans to make a PCB for this (or to re-spin the RGBtoHDMI board with this instead of the 74LS08)? I might have a go at it sometime but I'll have to learn how to use Kicad first. A small sub-board might work but I'm n...
by IanB
Sun Feb 03, 2019 3:58 am
Forum: hardware
Topic: Pi based Prisma 3 emulation connected via 1Mhz bus
Replies: 15
Views: 1030

Re: Pi based Prisma 3 emulation connected via 1Mhz bus

One thing I noticed during initialisation is that it copies default palettes and overlay definitions from NVRAM to the onboard RAM. So am wondering if a dump of the Am9864 may be required? Looks like it should be dumped. I don't think I ever used the NVRAM feature so it's likely still set at the fa...
by IanB
Sun Feb 03, 2019 3:50 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I've made a composite video adapter for the HDMI interface for use with computers with a monochrome composite output such as the ZX81, Nascom, UK101, Apple II, TRS80 etc. The circuit is essentially the same as the Y and SYNC comparator part of Hoglet's Atom interface but with the active back porch c...
by IanB
Mon Jan 28, 2019 5:07 pm
Forum: hardware
Topic: Pi based Prisma 3 emulation connected via 1Mhz bus
Replies: 15
Views: 1030

Re: Pi based Prisma 3 emulation connected via 1Mhz bus

Pernod wrote:
Sun Jan 27, 2019 4:53 pm
My current emulation hangs during the initialisation of the Prisma. It would be very useful to know what, if anything, the Prisma is expected to output after initialisation. ie. switch Prisma on, then power up Beeb with Prisma 2.30 ROMs present.
It just outputs a blank screen on startup.
by IanB
Sun Jan 27, 2019 6:49 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I'm happy to make them configurable via the cmdline.txt file (and also update the UI menu options to reflect the configured values). I think they should be global named params, rather than mode specific params. Great I've got a few things on an the moment, so it may be a few days before I get aroun...
by IanB
Tue Jan 22, 2019 9:23 pm
Forum: hardware
Topic: IDE->SD/CF Adapters (What works and what doesnt)
Replies: 22
Views: 968

Re: IDE->SD/CF Adapters (What works and what doesnt)

ADFS was based around the first IDE standard, which stipulated a DRQ timeout of 500ns, this was removed in later revisions. The patched ADFS 2.68 will resolve this issue Is there a patched version of ADFS for later versions of RISCOS like 3.71, 4.02 etc as I'd like to program an updated ROM sometime.
by IanB
Tue Jan 22, 2019 9:20 pm
Forum: hardware
Topic: IDE->SD/CF Adapters (What works and what doesnt)
Replies: 22
Views: 968

Re: IDE->SD/CF Adapters (What works and what doesnt)

The SD-CF adaptor I bought a year or so ago didn't work with RISC PC :( Or A5000 - I ended up using it with Wizzo in the A5000 under IDEFS. First time I've heard about problems with SD-CF adapters with a Risc PC/A7000 (not surprised about the A5000 though). What does the adapter identify itself as ...
by IanB
Tue Jan 22, 2019 7:31 pm
Forum: hardware
Topic: IDE->SD/CF Adapters (What works and what doesnt)
Replies: 22
Views: 968

Re: IDE->SD/CF Adapters (What works and what doesnt)

Does anyone have a recommendation for a SD or CF card solution for the RiscPC that works? Ideally, I'd like something I could plug into the motherboard and that would work with the cdrom. The most reliable method I found for a RiscPC is to use an SD to CF adapter plugged into a CF to IDE adapter as...
by IanB
Tue Jan 22, 2019 12:09 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

- HDMI clock calibration (including full Genlock capability to lock source and HDMI Vsync) I built a few more over the Christmas break and have just noticed a genlock problem with one of the new setups: Video is lost when resyncing the HDMI output with my Benq BL912 1280x1024 monitor which means it...
by IanB
Wed Jan 16, 2019 6:32 pm
Forum: hardware
Topic: Pi based Prisma 3 emulation connected via 1Mhz bus
Replies: 15
Views: 1030

Re: Pi based Prisma 3 emulation connected via 1Mhz bus

So it might be that soft-composing the four off-screen buffers into the displayed framebuffer isn't quite so challenging as in Dave's case. I think you're right. Based on my own observations when working on the BBC to HDMI code, the main issue appears to be variable latency when capturing pixels ra...
by IanB
Wed Jan 16, 2019 6:24 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I found the perfect case for this project: https://www.ebay.co.uk/itm/5X-Protective-Case-for-Raspberry-Pi-Zero-Raspberry-Pi-Zero-NOT-Included-Bl-U2S4/282946740170 The above is for a pack of 5 but other multiples are listed. The only build change I made was to solder the BBC RGB cable directly to the...
by IanB
Wed Dec 19, 2018 3:14 am
Forum: hardware
Topic: ARM1 versions / batches
Replies: 7
Views: 520

Re: ARM1 versions / batches

Most of pictures I have been able to find have been of the same batch of chips, dated week "8625", and labelled "AUTUMN" (is that a code name or a season?) Mine is also "8625" and "Autumn" The serial nunber of the unit is 25-ANC13-1000032 if that's any help BTW The PSU in the ARM evaluation unit ha...
by IanB
Sun Dec 16, 2018 12:28 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I built up few more of these yesterday and they all worked first time but I noticed that the auto calibration doesn't seem to work properly on the Electron: I set mux=1 and elk=1 in cmdline.txt but pressing the auto calibration button seems to turn the elk setting off during and after calibration re...
by IanB
Thu Dec 06, 2018 7:32 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

hoglet wrote:
Thu Dec 06, 2018 7:17 pm
3. Make the max clock error (ppm) configurable, with a default of 10,000ppm.
Sure, if you want to do it that way. I was just trying to avoid adding another tweak but I suppose these arbitrary values should be tweakable.
I suggest that setting a value of 0 switches it off.
by IanB
Thu Dec 06, 2018 7:10 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

Just a quick note to say the next software release is imminent (probably tomorrow). I just found a problem with the labyrinth fix: As the ZX80 uses a ceramic resonator it can have very large ppm errors, mine is currently over 8000ppm so it fails the >5000ppm test and uses the default clock which is...
by IanB
Tue Dec 04, 2018 5:39 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I've currently no idea why this is happening, but I suspect a race condition, i.e. the change from interlaced to non-interlaced happens while measure_vsync is running. That seems likely As a work around, I've quickly switched to determining interlace based on whether the number of lines is odd or e...
by IanB
Tue Dec 04, 2018 1:48 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I'll have a look at the Monsters issue after lunch. OK I'm pretty certain the problem is this: monsters changes from mode 7 to mode 2 triggering a recalibration calibrate_sampling_clock() determines interlace/non interlace and vsync length monsters changes interlace new interlace code waits to dete...
by IanB
Tue Dec 04, 2018 1:04 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

The bit I didn't like was inhibiting genlock when the sampling clock exceeded the maximum PPM error. Here's my rational: 5. The only reason genlock can fail to lock is insufficient range on the HDMI clock, which I have just fixed No problem, it was only included as a fallback if the HDMI lock range...
by IanB
Tue Dec 04, 2018 12:44 pm
Forum: projects
Topic: A new MENU system for MMC/Gotek
Replies: 67
Views: 2519

Re: A new MENU system for MMC/Gotek/ (GOTEK working)

Nice work! A couple of things I noticed so far, it doesn't run if the Advanced Disk Toolkit ROM is installed and Ski Slalom (RH Software) hangs at the key / joystick / lightpen menu.
by IanB
Tue Dec 04, 2018 12:12 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

There seems to be a problem with Acornsoft Monsters which ends up with the red bar at the top of the screen. Acornsoft defender also exhibits this behaviour. It looks like they are switching to mode 2 with the default interlace type (in my case interlace on) then accessing the 6845 directly to inver...
by IanB
Tue Dec 04, 2018 12:39 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

I'm not really sure how best to deal with this now. I'll wait for your input before I push anything further. I'm going to finish for tonight and pick this up again tomorrow morning. I'll look at extending the range of the PLLH setting code. I've pushed the follow changes to get labyrinth working: I...
by IanB
Mon Dec 03, 2018 4:16 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

The only outstanding bug I'm aware of is the one we noted a while ago concerning enabling or disabling interlace. I've just pushed a change that should fix this: https://github.com/hoglet67/RGBtoHDMI/commit/5a12981ac7d97cf9e2c418c2b3df1d275c487f34 Looks good, I had to do a manual merge as I made so...
by IanB
Mon Dec 03, 2018 1:03 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

Here's a modified version of ski slalom with collision detection and the finish line removed so it can be used as a continuous sideways scrolling test:
SidewaysScroll.ssd
(8.5 KiB) Downloaded 10 times
by IanB
Mon Dec 03, 2018 3:23 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

Do either of you have anything that needs to be added before this? I've created a pull request with some changes and bug fixes to the genlock introducing some hysteresis and also restricting the range to 5 - 265 to allow that to work properly. (The single buffer OSD only starts to disappear around ...
by IanB
Thu Nov 29, 2018 2:08 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

If vlock is set to a small value (like 1), it seems to resolve the flickering menu issue with single buffering, which is a nice side effect. That was one of the main reasons for doing it so I could switch to single buffered to remove the lag. It may be worth adding the vlock setting to the command ...
by IanB
Thu Nov 29, 2018 3:55 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 621
Views: 25242

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

Any chance I can persuade you to start using git? It makes concurrent development like this much easier, although not completely pain free I've forked your repository on github and made 2 commits: 1. bob deinterlace (should be same as above files) 2. vertical genlock https://github.com/IanSB/RGBtoH...