Search found 10330 matches

by hoglet
Tue Aug 03, 2021 9:38 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

If I did have the resistor packs fitted... what difference would that make? Why wouldn't I be able to perform this test? Sorry for my crude misunderstanding of electronics. I've got a lot to learn. The CPLD samples the RGB value of 4 successive pixels and passes these to the Pi via GPIO13..2 in the...
by hoglet
Tue Aug 03, 2021 8:55 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

It would be great if there's a table of expected voltages on each pin so that it's easy to do a straightforward check. Basically, you are checking GPIO13..2 should all be 3.3V BUT, this test is only possible because: - you don't have the resistor packs fitted (which act as pull downs on the RGB inp...
by hoglet
Tue Aug 03, 2021 7:55 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

Looking at your measurements (some of which are not visible in the photo), GPIO13 definitely looks suspect. There is probably a dodgy connection where GPIO13 connects to the CPLD, which is at pin 1. Try checking pushing down on pin 1 with a sharp plastic object and see if the yellow line vanishes. I...
by hoglet
Tue Aug 03, 2021 5:02 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

Odds on that I've got another pin problem, but if I can get a clue as to where the problem likely is... rather than having to re-work the whole chip again... it would be a real bonus! OK, I understand now. I was confused by the grey screen, which is not normally present. Without the resistor packs ...
by hoglet
Tue Aug 03, 2021 4:02 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

That all looks fine to me.

Code: Select all

CPLD  Design: 3-12_BIT_BBC
CPLD Version: 7.9
Is there still an issue with this particular board? (i.e. is it behaving any differently to the others)

Have you tried one yet with a Beeb?

Dave
by hoglet
Tue Aug 03, 2021 3:29 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

If you now have menu access, there is a Save Log FIle option somewhere.

This writes the log file out to the SD Card.

If you post that complete log file here, we can see what value it's reading back from the CPLD.

Dave
by hoglet
Tue Aug 03, 2021 3:24 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

Two are giving me, "CPLD is unknown: Select correct CPLD" when I try and program them. These are two of the chips I had to "melt" off the board because I got it wrong... two of the "miracle" boards, in that it'll be a miracle if they work. Anyone know what else I shoul...
by hoglet
Mon Aug 02, 2021 11:22 am
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

msknight wrote:
Mon Aug 02, 2021 11:19 am
Hmm.... looks like a standard USB cable with a few pins to connect to the Pi. No need to buy anything. I can knock that up this evening.
It's a USB to 3.3V serial cable with a USB UART embedded in the plug, not just a direct connection to USB.
https://thepihut.com/products/usb-to-ttl-serial-cable
by hoglet
Mon Aug 02, 2021 11:10 am
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

Note that the resistor packs are not installed, as they won't arrive for another two weeks at least, but with no connection to a machine, that shouldn't matter... right? I should still get a menu... shouldn't I? A few points.... See Ian's earlier post about the role of the resistor packs: https://s...
by hoglet
Fri Jul 30, 2021 8:39 am
Forum: programming
Topic: Possible to run Acorn BBC Micro Language ROM on another 6502 system?
Replies: 74
Views: 2039

Re: Possible to run Acorn BBC Micro Language ROM on another 6502 system?

However Lisp still seems to think there is an escape condition so it doesn't evaluate or print anything. That is the next mystery to resolve! It may be that LISP is checking the escape flag directly at &FF. Does you OS Environment maintain a copy there? Here's what the Advenced User Guide has t...
by hoglet
Tue Jul 27, 2021 3:48 pm
Forum: 8-bit acorn hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 1755
Views: 178642

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

OK - I think I've just made an expensive booboo. I've gone for the parts and boards for the generic 12 bit board... but I need to hook up my BBC B. Have I just bought all the wrong kit? I found this out when I started investigating the pins to wire up the BBC RGB and it didn't make sense. How much ...
by hoglet
Sun Jul 25, 2021 11:06 am
Forum: 8-bit acorn hardware
Topic: Faulty BBC
Replies: 7
Views: 216

Re: Faulty BBC

I was a bit sceptical that a BBC would run at all without a 6845 as it's responsible for keeping the DRAM refreshed. So I just tried with one of mine (with only the BASIC and OS ROMs) and it does in fact boot, and I was able to type in a simple program: 10 FOR A=1 TO 10 20 VDU 7 30 NEXT Whether this...
by hoglet
Sun Jul 25, 2021 10:43 am
Forum: 8-bit acorn hardware
Topic: Faulty BBC
Replies: 7
Views: 216

Re: Faulty BBC

It sounds like the 6845 is driving the data bus when it shouldn't be, causing the machine to hang on boot. There are two things that could cause this: 1. the 6845 iteslf being faulty 2. the 6845 chip select (pin 25) being held low, due to a fault in IC26 If you have access to a known working 6845 th...
by hoglet
Fri Jul 23, 2021 7:04 pm
Forum: 8-bit acorn hardware
Topic: A blitter for the beeb?
Replies: 169
Views: 23975

Re: A blitter for the beeb?

This sort of timing issue usually falls into one of three buckets: 1 - the system clock is just too fast for certain logic paths (that start and end on the FPGA, but might go via asynchronous SRAM) 2 - timing differences with the signals that pass onto the BBC board (cf an NMOS 6502A) 3 - hold time ...
by hoglet
Fri Jul 23, 2021 6:45 pm
Forum: 8-bit acorn software: other
Topic: Cannot Boot to Acorn CP/M
Replies: 22
Views: 421

Re: Cannot Boot to Acorn CP/M

Pernod wrote:
Fri Jul 23, 2021 6:43 pm
Interesting, I can duplicate the issue in MAME using Disc Doctor 1.09. The later versions 1.0A and 1.0B work without issues.
Yes, very interesting.

Is this just with BASIC, DFS 2.26 and Disc Doctor 1.09?

Does the order of the ROMs matter?

Dave
by hoglet
Fri Jul 23, 2021 6:36 pm
Forum: 8-bit acorn software: other
Topic: Cannot Boot to Acorn CP/M
Replies: 22
Views: 421

Re: Cannot Boot to Acorn CP/M

John_Newcombe wrote:
Fri Jul 23, 2021 6:23 pm
It was Disc Doctor 1.09.
Thanks.

I will try to reproduce this to work out what the issue actually is.

Dave
by hoglet
Fri Jul 23, 2021 4:13 pm
Forum: 8-bit acorn software: other
Topic: Cannot Boot to Acorn CP/M
Replies: 22
Views: 421

Re: Cannot Boot to Acorn CP/M

What version of Disc Doctor were you using?

(*HELP should tell you this)
by hoglet
Fri Jul 23, 2021 4:08 pm
Forum: 8-bit acorn software: other
Topic: Cannot Boot to Acorn CP/M
Replies: 22
Views: 421

Re: Cannot Boot to Acorn CP/M

Glad you eventually got it sorted.... :D
by hoglet
Fri Jul 23, 2021 8:16 am
Forum: 8-bit acorn software: other
Topic: What's at SHEILA &FE8E on the BBC Master series computer?
Replies: 5
Views: 285

Re: What's at SHEILA &FE8E on the BBC Master series computer?

As far as I know, this is an unsolved mystery! The &FE80-&FE9F block corresponds to the modem slot on the Master. As far as I know, the only Acorn hardware designed and released for this slot was: - the Acorn internal AIV Host Adapter which is well documented on Simon's Domesday site - the A...
by hoglet
Thu Jul 22, 2021 5:55 pm
Forum: 8-bit acorn software: other
Topic: Cannot Boot to Acorn CP/M
Replies: 22
Views: 421

Re: Cannot Boot to Acorn CP/M

There are two things you could provide that will help here:

1. A complete list of the ROMs installed in your BBC (and the slot numbers)

2. An upload of the actual CP/M disk image you are using.
by hoglet
Thu Jul 22, 2021 5:53 pm
Forum: 8-bit acorn software: other
Topic: Cannot Boot to Acorn CP/M
Replies: 22
Views: 421

Re: Cannot Boot to Acorn CP/M

RobC wrote:
Thu Jul 22, 2021 4:12 pm
If the OSGBPB Tube transfers don't work, that might explain what you're seeing...
I think CP/M uses OSWORD &7F for disk access, not OSGBPB.
by hoglet
Thu Jul 22, 2021 12:54 pm
Forum: 8-bit acorn hardware
Topic: A blitter for the beeb?
Replies: 169
Views: 23975

Re: A blitter for the beeb?

The multi-cycle paths are mainly to do with the T65 core. All the bus switching logic etc runs off a single "fast" 128MHz clock - but the t65 core only has its enable input set once every 8 cycles to effectively run at 16MHz. This seemed like the easiest way to do things rather than a lot...
by hoglet
Tue Jul 20, 2021 6:10 pm
Forum: 8-bit acorn software: other
Topic: Acorn Z80 and Gotek issue, help needed.
Replies: 8
Views: 246

Re: Acorn Z80 and Gotek issue, help needed.

Do you have both RAMFS and DFS ROMS fitted?

What slot numbers are they in?

Does running from DFS work if you remove or disable the RAMFS ROM?

Dave
by hoglet
Tue Jul 20, 2021 5:53 pm
Forum: 8-bit acorn hardware
Topic: The Beeb's cassette storage input circuit
Replies: 120
Views: 3108

Re: The Beeb's cassette storage input circuit

For those programs (protection systems) which depend critically on the length of the lead-in detection, I do wonder exactly what they are doing. Are they intentionally, or accidentally, dependent on it? I'm not conviced there are any such programs! Certainly OS 1.20 doesn't seem to care. In OS 1.20...
by hoglet
Tue Jul 20, 2021 5:37 pm
Forum: 8-bit acorn emulators
Topic: beebjit-0.9.6 release: a story in pictures
Replies: 71
Views: 2172

Re: beebjit-0.9.6 release: a story in pictures

However, see my other post -- my latest theory is that 0.15s of carrier tone might be enough if it occurs right after a data block, because of the use of capacitance in the carrier tone detection circuit. Curious if you think that's plausible, or that I'm full of nonsense. An alternate theory might...
by hoglet
Tue Jul 20, 2021 4:33 pm
Forum: 8-bit acorn hardware
Topic: The Beeb's cassette storage input circuit
Replies: 120
Views: 3108

Re: The Beeb's cassette storage input circuit

Some further info on the Ferranti ULA capacitor-based DCD timer. It's possible to craft a piece of high tone containing a half-cycle of low tone: Screenshot from 2021-07-20 16-32-37.png This discharges the capacitor to just below the logic threshold, and the DCD delay is then much shorter: about 10m...
by hoglet
Tue Jul 20, 2021 4:20 pm
Forum: acorn atom and acorn system series
Topic: ICE T65/Z80/6809
Replies: 1122
Views: 159037

Re: ICE T65/Z80/6809

I've ordered one of the eepizza boards as the GODIL40 boards are no longer available, with regards to the 6809E adapter board are the gerber files in the dev branch ( https://github.com/hoglet67/AtomBusMon/tree/dev/kicad/6809e/v1 ) good to use as is or are any modifications required? That's the mos...
by hoglet
Tue Jul 20, 2021 11:02 am
Forum: 8-bit acorn emulators
Topic: beebjit-0.9.6 release: a story in pictures
Replies: 71
Views: 2172

Re: beebjit-0.9.6 release: a story in pictures

We (meaning hoglet) might well be able to investigate this. Yes, this is interesting... See here: https://stardot.org.uk/forums/viewtopic.php?p=328708#p328708 Note that blipping the cassette motor is an action which discharges the capacitor. Yes it does, but interestingly not because of the diode D...
by hoglet
Tue Jul 20, 2021 10:58 am
Forum: 8-bit acorn hardware
Topic: The Beeb's cassette storage input circuit
Replies: 120
Views: 3108

Re: The Beeb's cassette storage input circuit

From the other thread I think it's a serial ULA thing. My current belief is that the serial ULA only clocks tape bits along to the ACIA if it thinks it is synced to a data stream. If I don't emulate it that way, a lot of the exotic tape loaders fail. I don't see any evidence that clock/data recovery...
by hoglet
Mon Jul 19, 2021 6:08 pm
Forum: 8-bit acorn software: other
Topic: Does anyone have a simple guide to dump a specific ROM from a BBC Micro to disk?
Replies: 21
Views: 403

Re: Does anyone have a simple guide to dump a specific ROM from a BBC Micro to disk?

Interesting, should a service ROM start with JMP &0000 ? The first three bytes of the ROM are the language ROM entry point, and this is only used if bit 6 of the ROM type byte (at &8006) is set. In this case, the ROM type byte is &80, so the ROM isn't a language ROM. Regardless of this,...

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