New Raspberry Pi to 1MHz bus interface

[Wheel_nut]

(Are those early Pi with a 26 way header, or with a 40 way header?)

The 2B has the 40 way Header but the 1B has the 26 way Header

[dp11]

The 1MHz code doesn't support 1B or 2B . 2B might work with a recompile.

[Wheel_nut]

The 1MHz code doesn't support 1B or 2B . 2B might work with a recompile.

How about the Tube Interface and Code? Would that work with the 1B ot 2B?

[dp11]

PiTubeDirect does support those Pis. You will find a pi zero is faster than both of those pis for the fast 6502.

[BigEd]

You do need to make arrangements to connect to the 26 pin header. One approach is to desolder the composite connector, at which point a 40 pin connector will just work. But it's tricky to desolder as it's so chunky. (Another approach (in theory) would be to fit a 26 pin connector to a 40 way cable, or a 40 pin connector to a 26 way cable. But no help when you want a cable-free direct connection.)

[KenLowe]

You do need to make arrangements to connect to the 26 pin header. One approach is to desolder the composite connector, at which point a 40 pin connector will just work. But it's tricky to desolder as it's so chunky. (Another approach (in theory) would be to fit a 26 pin connector to a 40 way cable, or a 40 pin connector to a 26 way cable. But no help when you want a cable-free direct connection.)

Please be aware that level shifter board needs to be close coupled / direct connected to the Rapsberry PI. You may start seeing issues if you introduce a cable between the level shifter and the Raspberry PI.

[Wheel_nut]

PiTubeDirect does support those Pis. You will find a pi zero is faster than both of those pis for the fast 6502.

Thanks dp11. I think tht I would like to try my Pi 1Bs on one of KenLowe's Tube interfaces. Although the Pi Zero may be faster, it is almost impossible to find one without paying the ridiculous Fleabay prices .... and I have a box-full of Pi 1bs and One Pi 2b wasting away.

You do need to make arrangements to connect to the 26 pin header. One approach is to desolder the composite connector, at which point a 40 pin connector will just work. But it's tricky to desolder as it's so chunky. (Another approach (in theory) would be to fit a 26 pin connector to a 40 way cable, or a 40 pin connector to a 26 way cable. But no help when you want a cable-free direct connection.)

Hi BigEd, Are you saying that only the first 26 Header Pins need to be connected to the Pi Tube Interface card for it to work? If this is the case, I will remove the Composite Spout which is actually quite easy for me, and use direct connection.

This is looking promising. ... and a good project while I am in solitary confinement.

[BigEd]

Please be aware that level shifter board needs to be close coupled / direct connected to the Rapsberry PI. You may start seeing issues if you introduce a cable between the level shifter and the Raspberry PI.

Good point! I have in the past run PiTubeDirect successfully over a cable, but using Kjell's level shifters, which might be different - and I might have been lucky. As you say, proceed with caution.

Are you saying that only the first 26 Header Pins need to be connected to the Pi Tube Interface card for it to work?

Yep.

If this is the case, I will remove the Composite Spout which is actually quite easy for me, and use direct connection.

Great!

This is looking promising. ... and a good project while I am in solitary confinement. :roll:

A good project at any time! I'm excited to see these twin level shifters, and the cunning arrangement for sharing the power supply. And it's good to think that a bunch of surplus Pi can be brought into play.

[Wheel_nut]

Please be aware that level shifter board needs to be close coupled / direct connected to the Rapsberry PI. You may start seeing issues if you introduce a cable between the level shifter and the Raspberry PI.

Hi KenLowe, Thank you for the caveat. I realise that I would need to extend the Tube Connecter either by cable or a IDC Connector to IDC Connector bodge and my intention would be to plug the RPi directly into your Level Shifter Interface board by removing the Composite Video Spout. I haven't taken any measurements but am optimistic that I can fit the RPi 1B under the Beeb. If not, I will resort to a cable extension.

I will add my requirement to your other thread and am happy to fund you in advance.

A good project at any time! I'm excited to see these twin level shifters, and the cunning arrangement for sharing the power supply. And it's good to think that a bunch of surplus Pi can be brought into play.

Yes, Being of that ilk myself, I am very fond of vintage things which may be a bit frayed at the edges but perfectly serviceable!

I now need to:
1) Get on KenLowe's schedule to obtain a Tube Level Shifter
2) Remove the Composite Video Spout from the RPi 1B - Question: Does it have to be the 512MB version or will the 256MB Version work?
3) Devise my connector extension to the 40 Pin Tube Connector
4) Download Hoglet's software for PiTubeDirect - Could you give me a Linky please and any special instructions
5) Load up an SD Card and plug it into the RPi
6) Have I missed something?

Edit: Corrected Point 2 RPi versions to 512MB and 256MB (not 128MB and 256MB as I originally stated)

[KenLowe]

I think I might have a possible solution without needing to remove the composite video connector from your RPi board. I should be able to get hold of some elevated 2x13 sockets that can be soldered onto the level shifter, and allow the level shifter to sit just proud of the composite video connector. I would also supply the board with 2x20 pin header on the Tube side, so you can connect it to the beeb via a standard 40 way ribbon.

I've attached a couple of photos showing what it might look like. The header I have in mind is actually a bit shorter than the mock up in the photos, so the board would almost sit on top of the yellow composite connector. It would cost an extra £3.50 (possibly less; waiting for price) for this special header. Let me know if you're interested, and I can get the header ordered up. Anyone else interested in this as a solution???

[Wheel_nut]

Hi KenLowe,

I would really like to install the RPi under the Beeb rather than on a Cable if I possibly can. Iam happy to remove the Composite Video Connector ... and the Ethernet Socket which will, I believe allow it to be fitted as in the picture below:

This would require the Tube connector on your board to be extended by about 15mm but I believe taht I can make up an extender from an IDC Connector soldered to a dual pinstrip if you can picture this. The Level Shifter Board would have to be installed first and the RPI then plugged straight down onto the Level Shifter.

Am I being over optimistic?

[KenLowe]

It may well work, but difficult to tell until you get all the parts and lay it out. Another point worth remembering is that you will likely need to power the RPi from an external source. You probably don't want to power up from the Tube port.

Even with the desire to fit the PI under the beeb, I could still fit an elevated 2x13 pin socket, which still may avoid you having to remove the composite video connector. The only difference with what I was suggesting is that I would supply the board with a standard 2x20 right angled tube socket instead of the pin header.

Total cost for the parts needed to do what you want is probably more that the cost of a RPi Zero V1.3, but I'm guessing cost is not your primary motivation here.

[Wheel_nut]

I hadn't thought that the startup surge from the RPi would last longer than the Beeb's startup delay but if this turns out to be a problem then I would rather just use a Pi Zero.

You are correct that the motivation for this project is more about the journey than the cost or the destination. I also love the elegance of your design which fits within the width of the Tube socket and the Pi Zero. The second motivator was to use the bunch of RPi's that I have.

So, what I would like is to buy one of your standard "Under" Tube Level Shifters to play with for now. This will allow me to use it with a Pi Zero if I don't like my solution which hopefully will not modify or damage the Level Shifter Board. I have already removed the Composite Video Connector and Ethernet Socket from one of my RPis so have no more damage to do.

I will add my request to your thread in the For Sale section and am happy to pay for it if you tell me how.

Robin

[KenLowe]

Folks,

Firstly, I must point out that I am no expert on the Music 5000 hardware, so I'm not going to be able to offer much in the way of support here. However, I thought I would post up a SCSI disk image that was used to help with testing both the emulated SCSI drive and the Music5000 hardware, and should allow you to get started with Music5000.

This works best on a BBC B with IntegraB or Master computer, that have 2 SWRAM banks available at banks 4 & 5 and have access to the *SRLOAD and *SRREAD commands
It will work with standard BBC hardware, but manual intervention will be required either to load the Music5000 ROMs into suitable RAM banks, or to install physical ROMs into the computer.

Assuming you have either a BBC B with IntegraB or Master computer and ADFS as the default file system, then:

• Extract the scsi0.dat file from the attached scsi0.zip archive, and drop it into the BeebSCSI folder on you SDCard. If the BeebSCSI folder doesn't exist, then create it.
• Shift-Break to auto boot.
• It will check to see if the ROMs already exist on the computer. If they don't exist then the ROMs will be loaded and the computer will reset. A further shift-Break will then be required
• If the ROMs exist on the computer, then the Music5000 software will automatically load and a tune should start to play from the internal speaker.
• Pressing f9 will load a jukebox, from which some other tunes can be played

If you just have a plain Model B (or B+), then I'll assume you've somehow managed to get the two ROMs (ANHF & Ample Nucleus) installed on your computer and that you also have ADFS installed on your computer. Note that a copy of the ANHF ROM image is located in the M5000 directory, and Ample Nucleus (ample) ROM image is located in the M5000.ROMS directory. I've no idea why they're in different directories!

• Extract the scsi0.dat file from the attached scsi0.zip archive, and drop it into the BeebSCSI folder on you SDCard. If the BeebSCSI folder doesn't exist, then create it.
• To start the Music5000 software, just switch into the M5000 directory, and *EXEC ppach2. A tune should start to play from the internal speaker
• Pressing f9 will load a jukebox, from which some other tunes can be played

[KenLowe]

Hi KenLowe,

I would really like to install the RPi under the Beeb rather than on a Cable if I possibly can. I am happy to remove the Composite Video Connector ... and the Ethernet Socket which will, I believe allow it to be fitted as in the picture below:
20200321_212123.jpg

This would require the Tube connector on your board to be extended by about 15mm but I believe that I can make up an extender from an IDC Connector soldered to a dual pinstrip if you can picture this. The Level Shifter Board would have to be installed first and the RPI then plugged straight down onto the Level Shifter.

Am I being over optimistic?

As a one off, I could get a few Tube level shifter boards built with a deeper body to remove the need to bodge together extenders. Once you have your concept proven, if you can let me know exactly how much I need to extend the board by, I can then have a look at it and get some costs.

Separately, I've also sourced a special 26 pin socket that allows the level shifter board to be close coupled to RPi, whilst avoiding the need to remove the yellow video socket on the RPi. I know this is probably not for you, but for others that would like to use their old RPi model B externally then this might be a good solution.

Alternatively, I received some proper 26 pin header extensions, so I was able to do away with my previous bodge, and now have PiTubeDirect running successfully on my old RPi Model B with these extenders. It's not quite as neat and tidy as the special 26 pin socket I mention above (as it's a bit bulkier), but it allows you to use a level shifter with a standard 40 pin socket. Here's a couple of photos showing this option. In this case, the board and the RPi Model B are both pulling power from the Tube port:

[1024MAK]

Is the stand an optional extra?

[Wheel_nut]

Hi Ken, I forgot to say "I may be a while" before venturing out of the Tent and into my cave!

Firstly, the Extender needs to be between 26mm and 27mm on the Tube Socket and this allows the RPi 1B (with the Composite Video and Ethernet Connectors Removed) to sit flat and directly onto your Level Shifter. The Ethernet Socket is removed to avoid interference with the 1MHz Bus Connector Retainer Clip.

I realise that this may not be for everybody because of the need to remove the Composite Video and Ethernet connectors but I am fairly deft with my soldering kit and really love having the RPi housed in the connector well. I am expecting to receive the parts for my proper extender next week and will post a picture of the finished article.

As an aside, I notice that PiHut have the Pi Zero in stock at £4.80 each plus £2.99 Postage BUT they are limiting purchaces to ONE!

This is my setup with my mock-up extender:

... and this is the Boot Screen:

... and running TUBEELT from Disc 45 on Beeb.MMB

[Wheel_nut]

Some further thoughts.

This discussion would appear to be under the wrong thread as the Header says "New Raspberry Pi to 1MHz bus interface" and the discussion that I started is about KenLowe's Tube Level Shifter and PiTubeDirect. However, in my defence, there doesn't appear to be a separate Thread or announcement of KenLowe's Tube Level Shifter.

Ken, I had a play with how your idea of building an extended single board for the full size Raspberry Pis might work and I think that this would be difficult to insert because the GPIO Header side would have to straddle the wall of the Connector Well and be inserted at an angle to the Tube Connector. This is further exacerbated by the slope of the Connector Well upwards from the axis of the Tube Connector pins. When in place, the GPIO Header is only about 3mm from the wall of the Connector Well.

My extender works because there is enough flex in the short cable to adapt to the angle of the slope of the Connector Well.

I think that if I was starting again, and PiHut had the Pi Zero in stock, I would do that. Of course, it doesn't solve the problem of installing the RPi 3B in the Connector Well.

[KenLowe]

This discussion would appear to be under the wrong thread as the Header says "New Raspberry Pi to 1MHz bus interface" and the discussion that I started is about KenLowe's Tube Level Shifter and PiTubeDirect. However, in my defence, there doesn't appear to be a separate Thread or announcement of KenLowe's Tube Level Shifter.

The Tube level shifter was never really meant to be a dedicated For Sale item, as there are several other vendors out there who already sell them. It was primarily built for those who needed to get power to the 1MHz level shifter from the tube port whilst running PiTubeDirect at the same time. As such, I'm not actively marketing the Tube level shifter. That is why they don't have a dedicated thread. That said, there have been quite a few people who have noted interest in the Tube level shifter, and I'm more than happy to offer them for sale for anyone who would like one.

Ken, I had a play with how your idea of building an extended single board for the full size Raspberry Pis might work and I think that this would be difficult to insert because the GPIO Header side would have to straddle the wall of the Connector Well and be inserted at an angle to the Tube Connector. This is further exacerbated by the slope of the Connector Well upwards from the axis of the Tube Connector pins. When in place, the GPIO Header is only about 3mm from the wall of the Connector Well.

My extender works because there is enough flex in the short cable to adapt to the angle of the slope of the Connector Well.

I was aware that there was a slope in the well, and my initial thoughts on this were that the two headers would need to be soldered in at an angle to compensate for the slope. Something like this. Not the best quality photo, but hopefully you get the idea:

[Wheel_nut]

The Tube level shifter was never really meant to be a dedicated For Sale item, as there are several other vendors out there who already sell them. It was primarily built for those who needed to get power to the 1MHz level shifter from the tube port whilst running PiTubeDirect at the same time. As such, I'm not actively marketing the Tube level shifter. That is why they don't have a dedicated thread. That said, there have been quite a few people who have noted interest in the Tube level shifter, and I'm more than happy to offer them for sale for anyone who would like one.

FWIW, I think that you should actively promote your Tube Level Shifter. It is a neat solution.

I was aware that there was a slope in the well, and my initial thoughts on this were that the two headers would need to be soldered in at an angle to compensate for the slope. Something like this. Not the best quality photo, but hopefully you get the idea:

Yes, that might work and I think that it is only the Tube Connector that would need to be angled. If the GPIO Header was mounted flat, it would allow the RPi to drop lower into the Connector Well.

I still think that there isn't enough play on the Tube Connector to allow insertion at the slight angle needed to clear the front wall of the Well.

[KenLowe]

***POSTING ON THIS THREAD SINCE THE FOR SALE THREAD IS CURRENTLY LOCKED FOR POSTING***

For those on the wait list in my For Sale thread, manufacturing of the next batch of 1MHz level shifters is now complete and awaiting courier pick up from the factory. It's taken a lot longer than the original quoted duration when I placed the order. I guess they're still catching up from the backlog when the factories were all closed down. Hopefully some of the extra time has gone on more stringent QA checking of the SMD component placement! I expect it to be at least a couple of weeks before these new boards arrive in the UK, but that may yet be impacted by the ongoing lockdown in the UK.

[KenLowe]

Of course, it doesn't solve the problem of installing the RPi 3B in the Connector Well.

Challenge accepted!

Turns out the RPi 3B is probably easier to install in the well than the RPi Model B. No components need to be removed from the RPi. I thought the ethernet socket might clash with the clips for securing the 1MHz bus ribbon, but it's actually the USB header that bottoms out on the underside of the beeb case. The ethernet socket sits nicely on top of the securing clips.

There's obviously not enough room to install the 1MHz level shifter under the beeb, but it still works with the remote option:

Tube level shifter with a couple of header extenders

With the RPi 3B plugged in

USB header bottoms out on underside of case

[Wheel_nut]

Wow! That's a piece of pure artistry and looks as though the RPi was designed to fit in the Beeb Connector Well!

Using the Header Stack also gives you the flexibility to adapt to the contour of the Well and stay as low as possible.

Is the Ethernet Connector on the RPi 3B lower than that on the 1B?

Did the Keyboard Fixing Screw Head or the Flange Head Case Screw interfere with the Level Shifter at all?

I once saw a compact MicroSD to SD Card adapter which was half the height. Cannot seem to find them now

I had considered padding the Mainboard with a couple of Nylon Washers under the Board to gain a couple of millimetres in the Well but there appears to be ample space with your Header Stack.

Challenge well WON!

[KenLowe]

Is the Ethernet Connector on the RPi 3B lower than that on the 1B?

It's exactly the same size.

Did the Keyboard Fixing Screw Head or the Flange Head Case Screw interfere with the Level Shifter at all?

The header extension appears to clear the keyboard fixing screw without any problem. I don't currently have the case screws in place (does anyone???), but I think it might clash with the level shifter if it was there, so that screw head might need to be insulated.

[mph1708]

First of all, thanks Ken for sending out the kit that arrived yesterday.
Both the underside Tube interface and the underside 1Mhz Bus interface are now fitted and working.
They are definately a very tight fit inside the "well" underneath the BBC Master.

Apart from a problem with a "duff" SD card, which was easily solved by using a brand new one, I did have a problem with a ROM clash.
I sometimes use my BBC Master with an external Datacentre, and it has been convenient to have an eprom of Datacentre RAMFS in slot 8.
What I found was that although the M5000 software will appear to run with the Datcentre RAMFS rom active, there will be no actual sound output from M5000.
Unplugging the Datacentre RAMFS cures the problem.

[KenLowe]

First of all, thanks Ken for sending out the kit that arrived yesterday.
Both the underside Tube interface and the underside 1Mhz Bus interface are now fitted and working.
They are definately a very tight fit inside the "well" underneath the BBC Master.

Apart from a problem with a "duff" SD card, which was easily solved by using a brand new one, I did have a problem with a ROM clash.
I sometimes use my BBC Master with an external Datacentre, and it has been convenient to have an eprom of Datacentre RAMFS in slot 8.
What I found was that although the M5000 software will appear to run with the Datcentre RAMFS rom active, there will be no actual sound output from M5000.
Unplugging the Datacentre RAMFS cures the problem.

Thanks for the feedback. I've not tried running M5000 with Datacentre, but given that they both use the 1MHz port, it's entirely possible that there might be some form of conflict. I'll try it with RAMFS in my setup shortly. Has anyone else come across this? With real M5000 hardware? I assume you just *UNPLUG the RAMFS ROM when you don't need it, and are not physically removing it?

Regarding fitment under the BBC Master, I'm hoping the 1MHz adaptor was slightly easier to fit than the Tube adaptor? I'm trying to source a 40 pin right angle socket that's not quite as deep as the ones I'm currently using. The ones I'm currently using are about 1mm deeper than the equivalent 34 pin right angle socket used on the 1MHz board. Unfortunately, I can't make the boards any smaller as this would impact the fitment under the standard beeb. As I've said previously, it's a bit of a compromise, but hopefully it works for everyone.

[dp11]

It is a known issue that the Datacentre interferes with M5000. See viewtopic.php?f=3&t=17222&p=238568&hili ... re#p238568

[mph1708]

I don't think Acorn ever envisaged that the "well" beneath the BBC Master would ever be home to two additional ARM powered computers.
And with that in mind, it something of a minor miracle that everything fits - so I would say that the design compromises are about right.
I have been trying out the 1 Mhz unit in BeebSCSI Harddisc mode.
It does feel a little bit different than an actual BeebSCSI unit, but that is not surprising seeing that it is totally different hardware.
I find myself missing the *SCSIJUKE functionality from the BeebSCSI Utilities ROM though.

[KenLowe]

I have been trying out the 1 Mhz unit in BeebSCSI Harddisc mode.
It does feel a little bit different than an actual BeebSCSI unit, but that is not surprising seeing that it is totally different hardware.
I find myself missing the *SCSIJUKE functionality from the BeebSCSI Utilities ROM though.

I've not tried it myself yet, but I think it should work just the same? Have you tried?

[dp11]

The Beebscsi utility should still work. How does scsijuke not work?