Search found 466 matches

by simoni
Wed May 01, 2019 5:06 pm
Forum: hardware
Topic: Issue 4 Beeb - Modification
Replies: 2
Views: 137

Re: Issue 4 Beeb - Modification

At a glance I'd say it was to modify the VREF voltage to the ADC IC (the diodes are used to drop the voltage from the 5V supply). Since D6,7 and 8 are most likely still in place, you can safely remove it (leaving it in place will probably cause analogue joysticks to have a modified swing).
by simoni
Sun Apr 28, 2019 8:20 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

I have seen issues where it causes a crash after about 3minutes.
Can you let me know the BeebSCSI board revision and firmware version you were running when you observed the crash?
by simoni
Fri Apr 26, 2019 11:33 am
Forum: hardware
Topic: Music 5000 clone in Kicad - Work in progress
Replies: 26
Views: 879

Re: Music 5000 clone in Kicad - Work in progress

With the original spec 74LS ICs it's drawing about 400mA off the wall-wart, and the chips get quite warm. As an experiment I replaced about a dozen of the 74LS chips with 74HC equivalents I had in my parts store - and it appears to still function OK, but now draws about 300mA, and they don't get so...
by simoni
Wed Apr 17, 2019 7:46 pm
Forum: hardware
Topic: Raspberry Pi to 1MHz bus interface
Replies: 80
Views: 3604

Re: Raspberry Pi to 1MHz bus interface

Perfect, thanks! The BBC Master is my usual go-to machine, and these boards don't usually fit underneath. Whilst the converter is fine for the Model B, mounting on a Master might be a little more tricky from a signal quality perspective which is why I wanted to take a look at it. I'll put the design...
by simoni
Wed Apr 17, 2019 5:33 pm
Forum: hardware
Topic: Raspberry Pi to 1MHz bus interface
Replies: 80
Views: 3604

Re: Raspberry Pi to 1MHz bus interface

Using diodes and resistors as a bidirectional level converter is a fairly standard trick (with caveats around pull-down): http://www.hobbytronics.co.uk/schottky-logic-level-conversion The advantage of the approach is that it's cheap; the disadvantage is that it skews the signal edges and doesn't wor...
by simoni
Tue Apr 16, 2019 7:13 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

Doesn't surprise me that TIME is inaccurate over long measurements (although, in this case, it's a very short measurement, so the inaccuracy should be less on average). My point was really that there is a difference between the overall operation speed and the actual data transfer speed (the 'speed t...
by simoni
Tue Apr 16, 2019 3:53 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

The speed test code on domesday86.com is very simple, it also measures the total operation time (as opposed to just the data transfer speed). The data transfer speed is much higher than quoted, but it's not really a practical measurement. Since BeebSCSI is open-source, I didn't feel the need to 'bum...
by simoni
Mon Apr 15, 2019 3:35 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

If your code is repeatedly requesting a single 256 byte sector, it's going to be slow. It's also quite an unrealistic scenario since each read can pull back a couple of hundred sectors in a single call. You are basically driving the FAT stack in a manner which it isn't designed to be driven. It coul...
by simoni
Mon Apr 15, 2019 11:52 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

The first issue is probably due to the file server making multiple requests or sub-dividing the SCSI requests in some way. The second could be anything, from a BeebSCSI issue to a bug in the file server (I would guess that the file server is sending a STOP command to the LUN - which would cause Beeb...
by simoni
Mon Apr 15, 2019 5:15 am
Forum: hardware
Topic: Raspberry Pi to 1MHz bus interface
Replies: 80
Views: 3604

Re: Raspberry Pi to 1MHz bus interface

Is there a link to the PCB schematic and the source code? I don't like to plug anything new into my Acorn's unless I can see some schematics first :) Nice to see you've built upon my BeebSCSI code; I'm quite interested in how you did the CPLD part on the Pi; I'd been thinking about doing some Pi bar...
by simoni
Sun Apr 14, 2019 6:02 pm
Forum: hardware
Topic: The sound of BBC graphics!
Replies: 12
Views: 481

Re: The sound of BBC graphics!

The BBC's sound circuitry consists of a SN76489AN (which generates the sound), an LM324 quad op-amp which filters and pre-amps and a LM386 which acts as a power amp and drives the speaker. There are basically three sources of noise and distortion: 1) the chips themselves - they are not 'pro-audio' a...
by simoni
Sat Apr 13, 2019 11:46 am
Forum: hardware
Topic: Master IO Controller IC15 - Databus pins?
Replies: 4
Views: 141

Re: Master IO Controller IC15 - Databus pins?

There are used to select between internal and external tube and 1MHz bus. ( fe34) Thanks! Makes a lot of sense :) &FE34 is the ACCCON register though... the documentation (Acorn engineering news 1) says that ACCCON is contained in the Memory Controller though (IC20): https://github.com/simoninns/Ac...
by simoni
Sat Apr 13, 2019 10:41 am
Forum: hardware
Topic: Master IO Controller IC15 - Databus pins?
Replies: 4
Views: 141

Master IO Controller IC15 - Databus pins?

The IO Controller IC15 in the Master (CF30050) has two data pins D4 and D5 connected to the CPU databus CD4 and CD5.

Does anyone know why? :)

(Even better if someone can point me in the direction of some reverse engineering for this chip)
by simoni
Tue Apr 02, 2019 9:07 am
Forum: hardware
Topic: BBC Master 128 schematic in KiCAD
Replies: 9
Views: 364

Re: BBC Master 128 schematic in KiCAD

I've just added the schematic for the 65C102 Master CoPro to the GitHub too. This one was reverse engineered from the original PCB as no Acorn schematic has ever been found for this add-on (as far as I know!). Along with the AIV SCSI board (already published by me a while ago) - this means all the A...
by simoni
Mon Apr 01, 2019 3:50 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

Anyone verified that the filestore problem is solved with the new build? It would be good to get a little feedback beyond my own testing :)
by simoni
Sun Mar 31, 2019 3:27 pm
Forum: hardware
Topic: BBC Master 128 schematic in KiCAD
Replies: 9
Views: 364

Re: BBC Master 128 schematic in KiCAD

Thank you
You are very welcome :)
by simoni
Sun Mar 31, 2019 1:51 pm
Forum: hardware
Topic: BBC Master 128 schematic in KiCAD
Replies: 9
Views: 364

Re: BBC Master 128 schematic in KiCAD

There's a lot more information in a modern KiCAD schematic than there is available in a paper version; so it includes all the pin directions and types to allow the ERC to work - as well as the pins missing from the original schematic (and those marked as NC which should have had a signal). I also in...
by simoni
Sun Mar 31, 2019 10:27 am
Forum: hardware
Topic: BBC Master 128 schematic in KiCAD
Replies: 9
Views: 364

BBC Master 128 schematic in KiCAD

As part of some other work I'm doing I've produced a complete Master 128 schematic in KiCAD - complete with all custom IC definitions, power distribution, decoupling, etc. The design also passes ERC. The schematic is split into 30+ hierarchical sheets and drawn to assist functional understanding. If...
by simoni
Sun Mar 24, 2019 8:08 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

Ok, I've now finished testing and fixed a few things here and there... My testing on both ADFS and VFS now works flawlessly :) I've merged the dev branch and prepared a new release. You can get the 2.5 version from here: https://github.com/simoninns/BeebSCSI/releases/tag/V2.5 The release files inclu...
by simoni
Sat Mar 23, 2019 9:36 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

I've added the additional flush (seems to work now) and moved the other flush commands down a little (so it only flushes if the initial error check is successful) - I've also bumped the firmware version reporting to 2.05 I tested, formatting (using SuperForm), mounting, SCSI jukebox and also ran it ...
by simoni
Sat Mar 23, 2019 3:43 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

I've given the changes some testing and it doesn't seem to work correctly. The firmware is unable to MOUNT any other LUNs; so it works fine until you attempt a *MOUNT to switch to another LUN - then only power-cycling will bring it back to functioning. Looking at the debug traces I can see the follo...
by simoni
Tue Mar 12, 2019 5:19 am
Forum: hardware
Topic: A potential run of BeebSCSI 7.7 (the newest)
Replies: 87
Views: 2831

Re: A potential run of BeebSCSI 7.7 (the newest)

It means that whilst you can't attach the LV-ROM player via a host adapter to the external 1MHz bus and read it in ADFS (you just get a duplicated/triplicated data stream), you can attach an ADFS-formatted SCSI disc to the AIV board and read it in VFS. As I've mentioned elsewhere on this forum in t...
by simoni
Tue Mar 05, 2019 6:53 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

dp11 - I appreciate the hard work and I'll look into the pull request shortly.

I'm a bit swamped with work from the ld-decode project at the moment, which is why I'm a bit slow on the BeebSCSI side of things as it's using up 110% of my hobby time just to keep up :)
by simoni
Sun Dec 16, 2018 9:43 pm
Forum: for sale / freebies
Topic: Dutchacorn clearing out
Replies: 29
Views: 2083

Re: Dutchacorn clearing out

Just a note of thanks Paul, your generous donation will be put to good use!

/Simon (of Domesday86)
by simoni
Thu Nov 29, 2018 8:39 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 115
Views: 4372

Re: BeebSCSI 7_7

I been trying (and failing) to recreate this issue. I filled a 32Gb card with 20Gbs of SCSI juke directories, with each LUN at 512Mb. In every LUN I put 460Mbs of data and then ran speed tests reading and writing to the LUNs. As expected it gets a little slower, but measured in microseconds not seco...
by simoni
Sat Nov 24, 2018 6:01 am
Forum: hardware
Topic: BeebSCSI Electron - Chicken or Egg?
Replies: 8
Views: 425

Re: BeebSCSI Electron - Chicken or Egg?

SuperForm is included in the quick-start LUN image. Simply LOAD it from the existing LUN (rather than CHAIN) and then issue a *SCSIJUKE to change to another LUN set; then RUN the (already loaded) SuperForm. No floppy required :) You can also simply use the quick-start LUN image and rename the base d...
by simoni
Thu Nov 22, 2018 2:27 pm
Forum: hardware
Topic: VP410/VP415 laserdisc player digital audio?
Replies: 14
Views: 561

Re: VP410/VP415 laserdisc player digital audio?

All of the EEPROMs have been backed up and are available on the Domesday86 site. If you study the schematics even more, you'll discover there are 2 Intel microcontrollers in the player too with baked-in firmware; I've also removed them and rigged up some electronics to read their contents (also avai...
by simoni
Thu Nov 22, 2018 5:59 am
Forum: hardware
Topic: VP410/VP415 laserdisc player digital audio?
Replies: 14
Views: 561

Re: VP410/VP415 laserdisc player digital audio?

To be frank, the easiest way to play a disc with digital audio is to simply use a LaserDisc player that has that facility already. The Philips VP415 is a desirable player since it can understand the Domesday AIV format... but it's not actually a 'good' LaserDisc player by any means, especially when ...
by simoni
Thu Nov 01, 2018 2:47 pm
Forum: software
Topic: RISC OS relicensed: now under Apache 2.0!
Replies: 91
Views: 3853

Re: RISC OS relicensed: now under Apache 2.0!

OK, so essentially the "retro" part of your statement was irrelevant. That makes a lot more sense now, thanks. If that's how you choose to interpret it, then I guess it's up to you. Seems you read the first two sentences you quoted but not the third - which clearly (I thought) explained that it was...
by simoni
Thu Nov 01, 2018 4:18 am
Forum: software
Topic: RISC OS relicensed: now under Apache 2.0!
Replies: 91
Views: 3853

Re: RISC OS relicensed: now under Apache 2.0!

So I'm wondering, what would the development focus be for a "retro" hobby OS version of RISC OS? Are they incompatible with the above, or have I misunderstood you and your "retro" hobby OS is actually my "modern" hobby OS? I think this has been answered already above but just to be direct: It's not...