Search found 420 matches

by myelin
Sat Jul 14, 2018 7:08 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 207
Views: 7476

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

1920x1080 here!
by myelin
Wed Jul 11, 2018 5:30 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 207
Views: 7476

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

I'd be very interested in one (HAT + cable, shipped to San Francisco). Really glad to see this project reaching this stage :) Thanks Dave!

I'm probably going to be switching this between machines, and mounting it behind a monitor, so can I have a 100cm cable please?
by myelin
Tue Jul 10, 2018 9:24 pm
Forum: acorn atom
Topic: New Atom owner (soon)
Replies: 9
Views: 252

Re: New Atom owner (soon)

The only problem is the Y/PA/PB signals are relatively low voltage swing and tri-level (with some redundancy). Figure 10 in the 6847 data sheet best explains this. In the FPGA I use the differential LVDS I/O cells rather than external comparators. Each of PA and PB uses a pair of LDVS I/O cells, wh...
by myelin
Sun Jul 08, 2018 6:56 am
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 207
Views: 7476

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

hoglet wrote:
Sat Jul 07, 2018 1:13 pm
And lo and behold....
P1030968.JPG
(this was on an Issue 4 Elk)
Nice work! Looking forward to building up a few of these so I can have more than one machine with a display at once :)
by myelin
Sun Jul 08, 2018 6:55 am
Forum: acorn atom
Topic: New Atom owner (soon)
Replies: 9
Views: 252

Re: New Atom owner (soon)

8bitkick wrote:
Sun Jul 08, 2018 4:34 am
Until you get your MMC this might be useful. I just saw your post which prompted me to get in online...
Thank you! Yes, that'll be super useful! Are you bringing your Atom to VCF? There's a slight chance that mine might arrive in time...
by myelin
Sun Jul 08, 2018 2:41 am
Forum: acorn atom
Topic: New Atom owner (soon)
Replies: 9
Views: 252

Re: New Atom owner (soon)

What's you plan in terms of extensions? Not sure yet! AtoMMC2 seems like an excellent start. I like the look of your scan converter. Also, do you think your RGBtoHDMI hardware could be adapted to work here? I guess you would need comparators on the inputs...? I'm still figuring out how the whole Y/...
by myelin
Thu Jul 05, 2018 9:32 pm
Forum: acorn atom
Topic: New Atom owner (soon)
Replies: 9
Views: 252

New Atom owner (soon)

After staring at it on eBay for a couple of weeks, I finally cracked and bought the 200 euro Atom from backtoyourpast (pricey, but out of the Atoms I've seen whose owners will ship to the USA, it seemed bearable). So... I expect to be an Atom owner once it arrives in San Francisco :)
by myelin
Fri Jun 29, 2018 9:34 pm
Forum: hardware
Topic: Missing old/new Electron Expansions
Replies: 76
Views: 1195

Re: Missing old/new Electron Expansions

A couple of things got me thinking on various threads about what is not about for the Electron, a dredge of previous threads really. - With Daniel's freewifi for the serial port ... nowhere to plug it in on Electron ... and no serial port remakes - With Beebmasters Eco hubs .... dont think there wa...
by myelin
Fri Jun 22, 2018 11:24 pm
Forum: emulators
Topic: Econet for Arculator (and other emulators)
Replies: 13
Views: 646

Re: Econet for Arculator (and other emulators)

This does sound interesting, would be fun to connect a virtual arc to a virtual beeb over a virtual network :) Indeed! Hoping to do exactly that, and maybe have it use an USB Econet adapter (either my half-finished one, or flynnjs's one) as a bridge onto a real Econet. Not sure if that would play w...
by myelin
Fri Jun 15, 2018 4:39 pm
Forum: hardware
Topic: Multi-purpose podule with a Raspberry Pi
Replies: 8
Views: 283

Re: Multi-purpose podule with a Raspberry Pi

It looks like Circle (bare-metal Pi programming environment) has network, USB, and SD card drivers, plus some other possibly useful bits and pieces, so the approach of using the CPLD as a level shifter and doing everything in the Pi may actually work, as long as the drivers for current podules use s...
by myelin
Fri Jun 15, 2018 3:48 pm
Forum: hardware
Topic: Multi-purpose podule with a Raspberry Pi
Replies: 8
Views: 283

Re: Multi-purpose podule with a Raspberry Pi

meylin's idea is for all the communication between the host & Pi to be via the podule interface, similar to Pi-based coprocessors on the beeb. This will result in much tighter integration with the host, including the potential for it to be used to emulate existing IDE/network/etc. podules. But I'm ...
by myelin
Fri Jun 15, 2018 12:44 am
Forum: hardware
Topic: Multi-purpose podule with a Raspberry Pi
Replies: 8
Views: 283

Multi-purpose podule with a Raspberry Pi

An idea I've been batting around for a while, after acquiring an A3000 and reading all the threads about IDE and networking podules, is to make a simple podule (well, mini-podule) that contains a flash chip, a CPLD, and a header for a Raspberry Pi. The mini-podule interface has 35 pins, and we want ...
by myelin
Thu Jun 14, 2018 6:26 pm
Forum: introduce yourself
Topic: Hello from Charlottesville, VA, USA!
Replies: 15
Views: 465

Re: Hello from Charlottesville, VA, USA!

Welcome! And that is a *very* clean looking Beeb! The motherboard and keyboard look brand new...
by myelin
Wed Jun 13, 2018 8:11 pm
Forum: hardware
Topic: IDE interfaces - hardware details
Replies: 43
Views: 1477

Re: IDE interfaces - hardware details

Would you be open to uploading the .sch files (pictured in the PDFs), and possibly your kicad_pcb file with everything except the connectors and board layout deleted, for interested folks to use as a starting point? (That way we can build on a verified base.) Here are my KiCad projects, I encourage...
by myelin
Tue Jun 12, 2018 6:13 am
Forum: off-topic
Topic: ST micro ARM boards....
Replies: 10
Views: 434

Re: ST micro ARM boards....

Based on? You have to read the datasheet to see which IO are FT as some are but not others. The F103 has a dozen or so FT GPIO in the QFP on the cheap boards. Huh... and you're right. I just rechecked the STM32F103x8/xB datasheet, and it says that almost all the GPIO pins are 5V tolerant. I wonder ...
by myelin
Tue Jun 12, 2018 4:08 am
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 21
Views: 1889

Re: Electron unstable/fails to boot when Plus 1 is connected

Gave up and just started snipping pins... finally found that IC6 was the culprit. Snipping its pin 1 made the machine boot again, although the Plus 1 ROM and MGC were invisible. Scoping IC6 pin 1 showed that it was sitting around 0.1V, which would have kept the bank select register cleared. Tying it...
by myelin
Mon Jun 11, 2018 10:52 pm
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 21
Views: 1889

Re: Electron unstable/fails to boot when Plus 1 is connected

Usually with this sort of issue, there is a low resistance path to ground inside the failed chip. Start by measuring the resistance with the Plus one disconnected. It's probably a few hundred ohms. (Try the meter lead both ways around). Good thinking! My meter measured a total open circuit in one d...
by myelin
Mon Jun 11, 2018 8:02 pm
Forum: off-topic
Topic: ST micro ARM boards....
Replies: 10
Views: 434

Re: ST micro ARM boards....

Note that the STM32F103 (Cortex-M3) chips used in the cheap boards from China are not 5V tolerant. I believe the STM32F407 (Cortex-M4) chip used in the STM32 F4 DISCOVERY board has a lot of GPIOs that are 5V tolerant and use TTL signalling levels, so they can be connected directly to 80s/90s hardwa...
by myelin
Mon Jun 11, 2018 5:00 pm
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 21
Views: 1889

Re: Electron unstable/fails to boot when Plus 1 is connected

If you haven't found the Plus 1 schematic, it's attached. The reset line goes to 4 x ICs! Could be a short or a faulty IC i.e. one of the input's doing the pulling-down . . . Yep... one for the bank select latch, and three for the parallel port (main buffer, status input, and strobe output). I'm gu...
by myelin
Mon Jun 11, 2018 6:05 am
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 21
Views: 1889

Re: Electron unstable/fails to boot when Plus 1 is connected

Figured out part of what's going on... scoping up the reset pin, it's glitching low in sync with the rising edge of PHI0: Screenshot 2018-06-10 22.59.01 reset glitches.png I realized that I can get the same red/yellow pattern on screen by holding down BREAK on startup, so this confirms that the prob...
by myelin
Mon Jun 11, 2018 4:47 am
Forum: hardware
Topic: Electron unstable/fails to boot when Plus 1 is connected
Replies: 21
Views: 1889

Re: Electron unstable/fails to boot when Plus 1 is connected

Going through a lot of my old hardware right now to get it ready for exhibition at VCF West with 8bitkick and Lion , and the key thing to get going is my Plus 1... time to take another look at it :) I tried the fibre pencil approach when Dave suggested it (over a year ago now!) but it's still flaky:...
by myelin
Fri Jun 08, 2018 9:01 pm
Forum: emulators
Topic: Which is the canonical Elkulator repository?
Replies: 5
Views: 262

Re: Which is the canonical Elkulator repository?

GitHub would be great. I'm starting to understand Mercurial and Bitbucket a bit better after submitting a few changes to Arculator, but I'm still much more familiar with Git :)
by myelin
Thu Jun 07, 2018 4:41 pm
Forum: emulators
Topic: Which is the canonical Elkulator repository?
Replies: 5
Views: 262

Which is the canonical Elkulator repository?

I'm doing some work with Elkulator (getting it to replay bus cycles recorded from a real machine) and there seem to be several repositories around, none of which claims to be the canonical one. I'm guessing David Boddie's Bitbucket repo is the one to go with... is that right?
by myelin
Thu Jun 07, 2018 12:39 am
Forum: hardware
Topic: IDE interfaces - hardware details
Replies: 43
Views: 1477

Re: IDE interfaces - hardware details

As some of you may have noticed, with the help of John Kortink I've made and sold a few IDE interfaces. The building and posting of PCB's is not something I want to do long-term, so I'm making the designs available, so anyone can make IDE interfaces. This is awesome! Thank you Ian! I'm not currentl...
by myelin
Wed Jun 06, 2018 9:56 am
Forum: hardware
Topic: Electron Plus 3, some questions.
Replies: 15
Views: 401

Re: Electron Plus 3, some questions.

You should have a cream-coloured self adhesive label, which must be fixed to the Electron before attaching the Plus 3. This label is made from a metallic substance, and its purpose is to provide an electromagnetic field between the Electron and the Plus 3. This will improve the performance of your ...
by myelin
Tue Jun 05, 2018 12:59 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 147
Views: 10049

Re: Open Source Logic Analyzer Experiments

A project suggestion for anyone looking for one: embed 6502Decoder into b-em so you can capture machine state from a real machine and resume in the emulator (or use an attached machine as a monitor). Update: I've started on this, except with Elkulator, because I'm hoping to show off my heavily modif...
by myelin
Tue Jun 05, 2018 9:20 am
Forum: hardware
Topic: Myelin's FX2 Tube/Cartridge Adapter - Development and Support
Replies: 46
Views: 2232

Re: Myelin's FX2 Tube/Cartridge Adapter - Development and Support

It shouldn’t be hard to adapt this code to run directly on a Pi, using its GPIO pins for the JTAG connection. Will have to look into that when I’m back :) It’s also possible that openocd already supports this Pi GPIO method (see: https://electronics.stackexchange.com/a/101482 ), in which case you ca...
by myelin
Tue Jun 05, 2018 8:17 am
Forum: hardware
Topic: Myelin's FX2 Tube/Cartridge Adapter - Development and Support
Replies: 46
Views: 2232

Re: Myelin's FX2 Tube/Cartridge Adapter - Development and Support

I checked in my cpld programming notes: https://github.com/google/myelin-acorn-electron-hardware/blob/master/notes/pld_programming_and_jtag.md Also started on a simple cpld programmer Arduino sketch, which should make it possible to program the cplds on my boards with just an Arduino Leonardo or Pro...
by myelin
Mon Jun 04, 2018 12:28 pm
Forum: hardware
Topic: Myelin's FX2 Tube/Cartridge Adapter - Development and Support
Replies: 46
Views: 2232

Re: Myelin's FX2 Tube/Cartridge Adapter - Development and Support

That’s right... I’ve started committing .bit and .svf files into git, so people can do that, but have been fairly haphazard about it so far. Need to do a proper sweep through all the projects and bring them all up to date!