Search found 616 matches

by cmorley
Sat Sep 22, 2018 8:59 am
Forum: hardware
Topic: Model B serial speeds
Replies: 11
Views: 312

Re: Model B serial speeds

From testing 38,400 works with no errors in data transfer below 32K, but text replies (eg *CAT, *EX) start dropping characters, so I tend to stick to 19,200. I wonder if this is the PC end or the BBC end causing this? I found using the naff USB adapter that full duplex caused errors (characters PC-...
by cmorley
Fri Sep 21, 2018 8:01 am
Forum: hardware
Topic: Model B serial speeds
Replies: 11
Views: 312

Re: Model B serial speeds

There's faster version of the CRC-16 code on the Wiki . I found that one when searching yesterday. I just tried it and it is 220 cycles per byte it seems. My code does lda ACIAD:jsr CRC so I need to strip the pointer inc and counter code which will win me some so I'll give it a go! Edit: I'll loose...
by cmorley
Fri Sep 21, 2018 7:35 am
Forum: for sale / freebies
Topic: Free: monitor & teletext adapter
Replies: 9
Views: 211

Re: Free: monitor & teletext adapter

If the discs are important (?) they do clean-up and usually work OK . . . Dave H :D I found disc images on the internet so I can get it working with a Gotek or write new floppies. It's just that otherwise I think I pretty much have the complete set of Master 512 bits including the quick reference c...
by cmorley
Thu Sep 20, 2018 10:23 pm
Forum: for sale / freebies
Topic: Free: monitor & teletext adapter
Replies: 9
Views: 211

Re: Free: monitor & teletext adapter

Good to hear it arrived safe and sound. I received the money for the P&P, thanks Colin. All the other disks I got in the same lot are mouldy too. Most were "backups" :wink: or data disks but there are the original Master 512 GEM disks... mouldy :( The master works after replacing the PSU caps appart...
by cmorley
Thu Sep 20, 2018 10:14 pm
Forum: hardware
Topic: Model B serial speeds
Replies: 11
Views: 312

Re: Model B serial speeds

Yes I could do something like that. My client code fits in one page at the moment so space is tight - which is why I'm using the MOS CRC. I could use a faster implementation - no point using the MOS one because it takes 10s to CRC 64K but only 16s to upload _and_ CRC @ 38400... 8s upload @ 76800 and...
by cmorley
Thu Sep 20, 2018 7:35 pm
Forum: hardware
Topic: Model B serial speeds
Replies: 11
Views: 312

Re: Model B serial speeds

Ha found a problem... I am using the MOS CRC code (CFS) to CRC received data. The poor CPU can't do the CRC in time! By my approximation it has around 260 cycles between bytes arriving @ 76800 baud. A quick speed test of the MOS CRC handler and it uses ~330 cycles per byte. #-o If only it ran at 3MHz!
by cmorley
Wed Sep 19, 2018 6:04 am
Forum: programming
Topic: Beeb Shadow RAM, load image from disc?
Replies: 12
Views: 268

Re: Beeb Shadow RAM, load image from disc?

I think the *fx108 (osbyte 108) solution is better. Why go to the bare metal with more typing when the OS has it built in?
by cmorley
Wed Sep 19, 2018 4:35 am
Forum: programming
Topic: Beeb Shadow RAM, load image from disc?
Replies: 12
Views: 268

Re: Beeb Shadow RAM, load image from disc?

On the BBC Master, shadow screen memory can I think be addressed with *SAVE/*LOAD using address FFFDxxxx e.g. *LOAD file FFFD3000 Haven't tried this myself though... See: http://mdfs.net/Docs/Comp/BBC/MemAddrs Not with DFS... ADFS maybe. Lower down in JGH's notes of that file. DFS 2.xx onwards only...
by cmorley
Tue Sep 18, 2018 8:54 pm
Forum: projects
Topic: 160 x 128 mode
Replies: 21
Views: 409

Re: 160 x 128 mode

Thanks Mark. Define "too low"?! Do you think the current 128us approach is going to cause any damage? Any multiple of 64us should be just fine as the TV horz deflection is free running in the event of no signal as Mark says. Deviate from multiples of 64us and you'll affect the 15625kHz frequency. B...
by cmorley
Mon Sep 17, 2018 8:18 pm
Forum: for sale / freebies
Topic: New A3000 4MB memory
Replies: 16
Views: 454

Re: New A3000 4MB memory

Corum wrote:
Mon Sep 17, 2018 8:01 pm
If the ram expansion is also usable with the A3010 I'm interested in one
Sorry, the A3010 is a very different machine inside. I think it has zip sockets for extra RAM chips where the A3000 has a row of connectors for a daughterboard.
by cmorley
Mon Sep 17, 2018 3:22 pm
Forum: hardware
Topic: Mitsubishi 4853 floppy drive problems
Replies: 12
Views: 228

Re: Mitsubishi 4853 floppy drive problems

Is the chain terminated properly too? That could cause a head select problem I suppose.

My money is on the wiring or a connector though.
by cmorley
Mon Sep 17, 2018 2:43 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

Production PCBs on order from JLCPCB. I thought I'd try them after their brand ambassador danielj has been doing such a good job :D I made a slight adjustment to the dimensions (0.025") to make the connector fit better - the Acorn design of 3x SIL connectors is dreadful. :S I'll post an update when ...
by cmorley
Mon Sep 17, 2018 2:38 pm
Forum: hardware
Topic: Model B serial speeds
Replies: 11
Views: 312

Model B serial speeds

I do 95% of my dev on a PC and use serial to send to the Beeb and control it. Short story after having problems with the USB->RS232 adapter with the BBC I ordered a different one with a genuine FTDI chip in. My build tool normally squirts stuff over at 38400 (9600 with 6850 divider on 16x instead of...
by cmorley
Sat Sep 15, 2018 3:29 pm
Forum: for sale / freebies
Topic: Free: monitor & teletext adapter
Replies: 9
Views: 211

Re: Free: monitor & teletext adapter

OK. The monitor was previously used with a Master I'm told so I imagine it will do fine with any 80s machines. It might be an amber display.

Colin: TT adapter
Mark: monitor

If anyone else really wants the monitor then PM Mark + me and I'll throw a dice or something.
by cmorley
Sat Sep 15, 2018 2:37 pm
Forum: for sale / freebies
Topic: Free: monitor & teletext adapter
Replies: 9
Views: 211

Free: monitor & teletext adapter

I have a monochrome monitor and Morley (no relation) teletext adapter FOC to a good home. The monitor is genuinely untested and has no mains plug. It has marks on the plastic where the mains lead has been on it for years. I suspect it has been stored in a shed... could have some corrosion. I have th...
by cmorley
Sat Sep 15, 2018 2:24 pm
Forum: for sale / freebies
Topic: For Sale: A3000 for repair
Replies: 0
Views: 76

For Sale: A3000 for repair

I recently picked up a fairly cheap A3000. It has battery rot unfortunately. It leaked as far as the keyboard connectors and ruined the flexi - although conductive epoxy might work to repair the pads or glue on wires… I've seen this done. CJE have keyboards for A3000 £36 incl delivery. I removed the...
by cmorley
Sat Sep 15, 2018 7:50 am
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

That's what I got. I didn't want to spend a lot of time researching so I bought the Louis Rossmann (youtube) recommended setup. They have other microscopes & cheaper stands and I'm sure you can get a ring light from eBay for cheaper but I wanted quick and known good for hours use at a time. 0.7 (or ...
by cmorley
Fri Sep 14, 2018 6:10 am
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

0.7 for greater FOV and working distance. I bought the Amscope ring light so I knew it would fit (wasn't expensive).
by cmorley
Fri Sep 14, 2018 6:08 am
Forum: projects
Topic: Interlace stuff
Replies: 12
Views: 324

Re: Interlace stuff

This is what I did for my mode 0 640x512 Bad Apple demo. LCDs will incorrectly de-interlace the 256p giving you the same effect but with different timing. They introduce their own artefacts though due to various image enhancing :lol: filters.
by cmorley
Thu Sep 13, 2018 7:53 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

mattyj wrote:
Thu Sep 13, 2018 7:17 pm
Tad expensive at present.
Ring light and barlow lens on top of that too! :S
by cmorley
Thu Sep 13, 2018 5:22 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

mattyj wrote:
Wed Sep 12, 2018 11:38 pm
Looking good!
Thanks Matt. Have you pulled the trigger on a new microscope yet?
by cmorley
Thu Sep 13, 2018 4:38 pm
Forum: general
Topic: Today I received.....
Replies: 4792
Views: 327419

Re: Today I received.....

8-bit job lot from eBay I collected today. A super nice chap SE of MK was pleased to save this stuff which was otherwise destined for the tip. He offered me the the teletext adapter too FOC in case I can find a home for it :) Master (PSU caps have gone) + twin floppies. The master will be repairable...
by cmorley
Wed Sep 12, 2018 9:27 pm
Forum: off-topic
Topic: Cleaning PCBs
Replies: 8
Views: 314

Re: Cleaning PCBs

I'd use a dishwasher if I had one! My kitchen is too small :(

I soak in IPA, brush with a toothbrush, ultrasonic cleaner (with specific PCB cleaner detergent @ 70-75C), rinse under the tap (+ quick brush), soak in demin, bake at 120C fan for 25-30 mins.

I need a dishwasher!
by cmorley
Wed Sep 12, 2018 5:30 pm
Forum: for sale / freebies
Topic: New A3000 4MB memory
Replies: 16
Views: 454

Re: New A3000 4MB memory

One left in the first batch. Get your name down if you want it :)
by cmorley
Wed Sep 12, 2018 5:24 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

Pictures! :D Installed with the cheapo chinese connectors (nice connectors not in yet): Photo0747.jpg Installed: Photo0749.jpg Bare boards: Photo0750.jpg Chips - enough to cover those who've put their names down: Photo0751.jpg It works: Photo0754.jpg Bits awaiting assembly - bench needs a tidy :S : ...
by cmorley
Wed Sep 12, 2018 5:09 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

I ran a bunch of different games I have (I only have a small library of software for the A3000) and nothing skipped a beat so far. I made RAM disks and copied games to that and ran them from there to get the memory usage up. So far so good :) It is also amusing to slide the "next" up to max and star...
by cmorley
Tue Sep 11, 2018 4:25 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

The prototype PCBs arrived. I've soldered one up and it worked first time :S I haven't fitted any of the decoupling caps for a worse case test. Does anyone have a continuous running memory test or suggestion of an application which really hammers the memory? I have Goteks so a disk image would be he...
by cmorley
Sun Sep 09, 2018 8:27 pm
Forum: hardware
Topic: New A3000 4MB memory
Replies: 39
Views: 1022

Re: New A3000 4MB memory

It's designed to go perpendicular to the main board.
by cmorley
Sun Sep 09, 2018 8:24 pm
Forum: introduce yourself
Topic: Hello from Lancs, UK
Replies: 12
Views: 299

Re: Hello from Lancs, UK

Welcome! :)