Search found 7527 matches

by 1024MAK
Sat Jul 21, 2018 3:17 pm
Forum: hardware
Topic: Troubleshooting the Analogue Port with DB9 Joystick Adapter
Replies: 4
Views: 84

Re: Troubleshooting the Analogue Port with DB9 Joystick Adapter

The two fire buttons actually go to the Beeb's internal 6522 VIA chip, so are separate to the actual analogue channels. So ADVAL(0) only tells you about the fire buttons. As Tricky says, the four analogue channels are in two groups. One group of two for one joystick and another group of two for the ...
by 1024MAK
Sat Jul 21, 2018 9:15 am
Forum: off-topic
Topic: Using BBC BASIC to teach programming concepts in 2017
Replies: 89
Views: 2400

Re: Using BBC BASIC to teach programming concepts in 2017

Well, in Derby quite a lot of the buttons don't seem to work properly. You have to press them several times before they light up. Yeah, but you don't press the button again after the system has acknowledged your input (or do you?). But some people keep pressing the button until the traffic lights c...
by 1024MAK
Fri Jul 20, 2018 11:58 pm
Forum: off-topic
Topic: Using BBC BASIC to teach programming concepts in 2017
Replies: 89
Views: 2400

Re: Using BBC BASIC to teach programming concepts in 2017

In real world logic systems where micro-controllers and micro-processors are not involved, both parallel unsynchronised, sequential logic and synchronised logic is used. And of course, 8/16/32 bit micro-controllers and micro-processors can do sequential logic and parallel logic (within limits). They...
by 1024MAK
Fri Jul 20, 2018 10:55 pm
Forum: hardware
Topic: 2nd User port for Beeb?
Replies: 98
Views: 6269

Re: 2nd User port for Beeb?

Extra user ports using 74LS138.jpeg
Extra user ports using an 74LS138 in IC4 position.
Mark
by 1024MAK
Fri Jul 20, 2018 8:36 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 45
Views: 636

Re: BeebSCSI 7_7

Elminster wrote:
Fri Jul 20, 2018 7:44 pm
That is okay I found a cheap seller of holes on eBay :wink:
Polomints?

Mark
by 1024MAK
Fri Jul 20, 2018 5:45 pm
Forum: general
Topic: *TAPE baud rates
Replies: 16
Views: 233

Re: *TAPE baud rates

No, no, no, no!
It's actual purpose is so you can enjoy the longer time for the program to load :mrgreen: :lol:

Mark
by 1024MAK
Fri Jul 20, 2018 1:25 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 45
Views: 636

Re: BeebSCSI 7_7

Duncan, all joking aside, good luck with the various projects.

If everything works out, are you intending on posting up your BOMs?

Mark
by 1024MAK
Fri Jul 20, 2018 1:22 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 45
Views: 636

Re: BeebSCSI 7_7

Elminster wrote:
Fri Jul 20, 2018 10:15 am
Nearly finished putting together parts order list for v7.7. 2 questions, all to do with holes.

What do I need to order for:

Fiducials:Fiducial_0.5mm_Dia_1mm_Outer
Tipex? :lol:
by 1024MAK
Thu Jul 19, 2018 7:59 pm
Forum: general
Topic: "Outline specification for the BBC MICROCOMPUTER system"
Replies: 203
Views: 16285

Re: "Outline specification for the BBC MICROCOMPUTER system"

Yeah, except having a 'custom' chip did not stop all clones. For example, there were unlicensed clones of the ZX81 and of the ZX Spectrum. The most widely available clone of the ZX81 had it's own ULA that included features beyond that of a real ZX81! Of course, as laws changed and original manufactu...
by 1024MAK
Thu Jul 19, 2018 7:47 pm
Forum: for sale / freebies
Topic: Worth Taking a Look At
Replies: 2656
Views: 218913

Re: Worth Taking a Look At

One for Acorn System enthusiasts: a large quantity of Vero Eurocard racking, collection only from Devon: https://www.ebay.co.uk/itm/Vero-Eurocard-racking-and-enclosures-for-electronic-equipment-and-PCBs/153103738578 I'd be bidding if it weren't so far away... Well, being a bit nearer, I'm taking a ...
by 1024MAK
Thu Jul 19, 2018 7:06 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 248
Views: 8208

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

I've always thought that the TV uses the centre of the pulse. No. In most analogue CRT TVs, the synchronisation pulses are used to synchronise two free running 'oscillators', one for the horizontal defection system and one for the vertical defection. Note that each 'oscillator' is actually a curren...
by 1024MAK
Thu Jul 19, 2018 1:04 pm
Forum: hardware
Topic: Fake 6502As
Replies: 4
Views: 187

Re: Fake 6502As

I get the impression that old chips that are no longer in production, but for which there is some demand, attract the interest of unscrupulous recycling companies. Due to the low cost of labour in parts of the Far East, we already know that they are good at "pulling" used chips (either from sockets,...
by 1024MAK
Thu Jul 19, 2018 9:25 am
Forum: hardware
Topic: SCART image quality
Replies: 9
Views: 232

Re: SCART image quality

Dave has hit the nail on the head. Please disregard the over simplified 'digital' is better perception that gets pushed by marketing people and others who jump on bandwagons. All LCDs are digital. It does not matter if the signal is analogue or digital, conveying information electronically always ha...
by 1024MAK
Wed Jul 18, 2018 5:53 pm
Forum: for sale / freebies
Topic: Worth Taking a Look At
Replies: 2656
Views: 218913

Re: Worth Taking a Look At

If you want to discuss copyright, please find a more suitable thread, or start a new one.

Mark
by 1024MAK
Wed Jul 18, 2018 3:42 pm
Forum: hardware
Topic: Model B paged ROM breakout board. Interest?
Replies: 43
Views: 2858

Re: Model B paged ROM breakout board. Interest?

IIRC some of those you mention are alternative positions for SMD parts. If you look at the schematic, these resistors are in parallel pairs. They are all optional so IIRC, no need to fit them unless you experience problems. The resistor for the LED (R1 or R2, but not both) depends on which colour an...
by 1024MAK
Tue Jul 17, 2018 4:06 pm
Forum: hardware
Topic: I2C 4 U
Replies: 172
Views: 12307

Re: I2C 4 U

Removing the resistor is easier, just put a soldering iron bit (a 3mm to 5mm chisel bit) nearly touching one side of the resistor, apply solder between the tip and each pad of the resistor, then use the iron to "flick" the resistor off the board... if needed, clean up any solder. Then clean the boar...
by 1024MAK
Tue Jul 17, 2018 1:18 pm
Forum: hardware
Topic: I2C 4 U
Replies: 172
Views: 12307

Re: I2C 4 U

When using the RTC chips from Maxim, this is my general advice: The datasheet from Maxim is clear in showing how to connect a primary cell/battery (non-rechargeable). The positive connection of the cell/battery should only be connected to the chip pin identified as V BAT . There should be no other c...
by 1024MAK
Mon Jul 16, 2018 3:10 pm
Forum: hardware
Topic: Electron +Plus 1 + AP5 + MMFS question(s)
Replies: 8
Views: 216

Re: Electron +Plus 1 + AP5 + MMFS question(s)

Information on the ROM and the ROM socket inside the Plus 1 here.

Mark
by 1024MAK
Mon Jul 16, 2018 2:54 pm
Forum: hardware
Topic: 2nd User port for Beeb?
Replies: 98
Views: 6269

Re: 2nd User port for Beeb?

It's possible to use a 74LS138 (or a 74HCT138) in place of the 74LS42 in position IC4, but the pin-outs are different.

Mark
by 1024MAK
Mon Jul 16, 2018 11:54 am
Forum: hardware
Topic: 2nd User port for Beeb?
Replies: 98
Views: 6269

Re: 2nd User port for Beeb?

Yes you can connect multiple devices on the 1MHz bus. Each device must use a different address (or address range if more than one address required per device). Only the last device should have line terminating resistors fitted. The length of the total length of ribbon cable between the 1MHz connecto...
by 1024MAK
Mon Jul 16, 2018 7:33 am
Forum: hardware
Topic: I2C 4 U
Replies: 172
Views: 12307

Re: I2C 4 U

I have seen I2C RTC modules on eBay based on these: Mark
by 1024MAK
Mon Jul 16, 2018 7:07 am
Forum: hardware
Topic: Electron RGB to VGI
Replies: 6
Views: 225

Re: Electron RGB to VGI

The RGB DIN connector is the same on both BBC B/BBC Master and Electron machines. However, the Electrons with earlier issue PCBs don't produce such a bright picture compared to the Beebs and the later Electron machines.

Mark
by 1024MAK
Mon Jul 16, 2018 7:03 am
Forum: hardware
Topic: Need help figuring out how to fix a couple of Beeb PSUs
Replies: 21
Views: 412

Re: Need help figuring out how to fix a couple of Beeb PSUs

GadgetUK164 wrote:
Sun Jul 15, 2018 8:23 pm
Do you happen to have the secondary side of that diagram? Just for future reference!
See the text in the post of mine that you quoted! I have not finished it yet.

Mark
by 1024MAK
Mon Jul 16, 2018 6:59 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 45
Views: 636

Re: BeebSCSI 7_7

Just to add to the confusion, the normal description in the U.K., is that for the normal dual pin IDC connectors, the PCB mounting part is the male plug. The connector that fits the male plugs, that attach to ribbon cable are line sockets. I am not sure that is right... Isn't a PCB box header a rec...
by 1024MAK
Sun Jul 15, 2018 7:04 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 45
Views: 636

Re: BeebSCSI 7_7

There's really only one type of cable connector; so it's just the type of socket on the BeebSCSI that can be varied. Sounds like you have a plan now though :) Just to add to the confusion, the normal description in the U.K., is that for the normal dual pin IDC connectors, the PCB mounting part is t...
by 1024MAK
Sat Jul 14, 2018 6:11 pm
Forum: hardware
Topic: Need help figuring out how to fix a couple of Beeb PSUs
Replies: 21
Views: 412

Re: Need help figuring out how to fix a couple of Beeb PSUs

i am a old men pc's are to moderne for me :) i can only work with paper , pencile and so on :shock: i even have plastic things with symbols #-o to draw :) Yeah, but I often work with paper and pen or pencil. It's only when I intend to publish or make a PCB board that I go to the effort of using a s...
by 1024MAK
Sat Jul 14, 2018 5:16 pm
Forum: acorn atom
Topic: new to atom: ram rom mmc joystick power
Replies: 23
Views: 440

Re: new to atom: ram rom mmc joystick

Phill (Prime) is a regular here, so PM him. Alternatively he is on Facebook.

Mark
by 1024MAK
Sat Jul 14, 2018 5:10 pm
Forum: hardware
Topic: BBC Master weirdness
Replies: 2
Views: 201

Re: BBC Master weirdness

AFAIK, all 3 1 / 2 " drives use an optical sensor or microswitch to sense track zero. And I believe nearly all 5 1 / 4 " drives do the same. For most drives, there is however no sensor to detect the last track (40 or 80). So if the system is trying to step beyond track 41 to 42, or 81 to 85 (depends...
by 1024MAK
Sat Jul 14, 2018 6:55 am
Forum: hardware
Topic: Electron +Plus 1 + AP5 + MMFS question(s)
Replies: 8
Views: 216

Re: Electron +Plus 1 + AP5 + MMFS question(s)

It's well worth while reading the Acorn Electron Expansion Application Note . Especially the bit about using ROMs. The Plus 1 ROM is ROM 12 (decimal). Note that the ROM socket on the Plus 1 PCB is not wired up so that a standard EPROM can be used. An alteration is needed if you want to fit a device ...
by 1024MAK
Sat Jul 14, 2018 6:30 am
Forum: hardware
Topic: Need help figuring out how to fix a couple of Beeb PSUs
Replies: 21
Views: 412

Re: Need help figuring out how to fix a couple of Beeb PSUs

This one: https://stardot.org.uk/forums/download/file.php?id=24205&mode=view :?: That's something I doodled. In the service manual there is a schematic diagram of the Beeb PSU. But there are some differences to the actual real life PSUs. Hence why I reverse engineered the important primary side. I h...