BBC Model B implementatation for myStorm BlackIce

[michaelengel]

Congratulations, another really great design! I'm still working on getting my 8080-based CP/M system running (which is mostly a matter of not having enough time...).

So what's next? Well, there's still plenty of space available:

After packing:
IOs 58 / 107
GBs 0 / 8
GB_IOs 0 / 8
LCs 4149 / 7680
DFF 1404
CARRY 298
CARRY, DFF 73
DFF PASS 913
CARRY PASS 47
BRAMs 20 / 32
WARMBOOTs 0 / 1
PLLs 0 / 2

After placement:
PIOs 41 / 107
PLBs 817 / 960
BRAMs 20 / 32

It might just be possible to squeeze in a 6502 Co Processor for the playing of Tube Elite!

Or even an OPC6 second processor for educational purposes.

This is one thing I am slightly confused about when using the icestorm toolchain.

When synthesizing for the iCE40HX4k on the BlackIce board, one has to use the options for the 8k part (i.e. "-d 8k" for arachne-pnr and "-d hx8k" for icetime). However, according to Lattice's iCE40 LP/HX Family Data Sheet (DS1040), the HX4k FPGA only has 3520 Logic Cells, whereas the 8k part has 7680.

In this system, more than 3520 LCs are used - however, the synthesis doesn't complain and (I assume, haven't tested it yet) the design actually works.

So, can anyone please shed a light on what might be going on there?

-- Michael

[Folknology]

I believe the limitations are made from within the Lattice toolchain, it appears to be an 8K die hence the settings

[hoglet]

There are a couple of things I should clarify concerning the video output formats.

In sRGB mode the video standard signal is identical to the original Beeb:
- 50Hz vertical
- 15.625KHz horizontal
- composite sync (on the hsync pin, vsync is unused).

This can be connected to a UK TV's SCART input (in sRGB mode) using a custom VGA to SCART cable.

In VGA mode, a line-doubler is used to give:
- 50Hz vertical
- 31.25KHz horizontal
- separate horizontal and vertical sync

This can be connected to an LCD monitor if it will sync down to 50Hz. Note, many won't so do check the specs.

Dave

[piers]

I believe the machxo3 part has a similar 'fix in the tools', the difference between the l &lf versions is the flash isn't tested and the tools disable it in the l version ...
This appears to be a way to have a larger product range without the cost of more designs

[ken.boak]

Dave,

This is great work - and went down well at the Hackaday Pub meet-up last night. Looking forward to taking news of it to the main Hackaday event today - and of course the Cambridge retro computer fair tomorrow.

I like the idea of a BBC B connected as a graphics/terminal front end to an OPC 6 as a co processor - the possibilities are tremendous and worth exploring..

Ken

[tony1tf]

Hi Dave

This is wonderful. I got my MyStorm board at the Chiphack2017 in Hebden Bridge.
I lived BBC Micros for decades, so am keen to get this going. I have just built a pmod to VGA converter on Veroboard, so am ready to try out the Beeb. However, I am not quite following your instructions for loading it. I have written the BEEB.MMB to a microSD card, and have dfu-util running on my Mac to upload icebootbeeb.raw to the ARM, but how to I get the beeb.bin file uploaded? Does the icebootbeeb.raw file load into EEPROM, so that I can disconnect the myStorm board and upload the .bin file to the other micro usb connector?

Tony

[hoglet]

but how to I get the beeb.bin file uploaded

You don't actually need to use the beeb.bin file at all, as it's already embedded in the icebootbeeb.raw firmware image. So just ignore it.

Once the FPGA bitstream has and ROMs have loaded, there should just be one LED lit - the red one (which is the Beeb's Caps Lock)

Dave

[tony1tf]

Hi DAve

Thanks for the info. I am still struggling, as I can't get dfu-util on my Macbook to talk to the board. I am sending the command:
dfu-util -p tty.wchusbserial410 -D icebootbeeb.raw

where either cu. or tty.wchusbserial410 is the port number of the righthand microUSB socket.
However I get messages back:
dfu-util: Invalid DFU suffix signature
dfu-util: A valid DFU suffix will be required in a future dfu-util release!!!
dfu-util: No DFU capable USB device available

So it seems that we are not talking correctly to the MyStorm ARM processor.
I had the ARM boot updated by Alan Wood at ChipHack to what was supposed to be the latest version.
Any suggestions as to how to debug?

Tony

[hoglet]

I had the ARM boot updated by Alan Wood at ChipHack to what was supposed to be the latest version.

All of the retrocomputer designs need custom ARM firmware, because the firmware includes the ROM images from the specific machine (e.g. OS 1.20, Basic II and MMFS for the Beeb Model B). These are loaded into external SRAM just after the FPGA is configured.

So you will need to do an ARM firmware update to run these designs.

Any suggestions as to how to debug?

I'm not going to be much use here, because I'm not a Mac user.

You need to be connected to the more central USB port.

The dfu command I do on Linux is:

sudo dfu-util -d 0483:df11 -s 0x08000000  -D iceboot.raw --alt 0 -t 1024

The -d parameter is optional if you only have one DFU capable device connected.

But the other are important.

As is running as root (i.e. sudo).

So all I can suggest is you try to replicate this on the Mac.

Also, make sure you have the libusb package installed, as I think dfu-util uses this.

Dave

[rshaw]

Also worth checking that you have removed the jumper to put the board into DFU mode.

[Folknology]

Make sure you can see the board, as Richard says make sure you remove the jumper on the RPi header then list devices using:

dfu-util -l

Also I seem to remember on Macs there is often more than one DFU device so you need to specify which one you are uploading to as David has shown using:

dfu-util -d 0483:df11 ..

[tony1tf]

Hi Guys
Thanks for all the suggestions to help a novice. The main problem was that I had completely forgotten about the jumper, and was using the wrong usb conector! I was able to use the linux command directly on the Mac, with the correct filename "icebootbeeb.raw".
Magic - it worked, and so did my hastily made veroboard pmod to VGA adaptor - attached photo shows it. Now to do the keyboard interface.
Thank you so much.
Tony

[electrified]

Unfortunately my monitor refuses to sync at 50hz!

I've been looking for a 4:3 monitor more suitable for retro gaming purposes, so now might be the time to get one

Found these lists of 50hz capable monitors:

http://wiki.icomp.de/wiki/Chameleon_Monitors
http://www.opencircuits.com/Minimig_display_compatibility

[tony1tf]

Hi Dave
Making progress now - my first keyboard (Medion - 5V 200mA)) didn't work with a cobbled together PS2 to PMOD interface powered from 3.3V, but a real Microsoft k/b (Digital Media Keyboard 3000) USB k/b with a USB to PS2 adaptor works fine, even though it says it is 5V (but only 100mA). Key mapping is a bit of a problem, though.
Now - a problem - I can't get the MMFS to work - it hangs on shift printscreen - shows:
BBC Computer
Model B MMFS
I have tried with a 4 and 8 GB card - both FAT32. One had additional files on, so deleted to just leave the BEEB.MMB directory with the BEEB.MMB file inside it, but no joy. I also tried replacing the BEEB.MMB directory with the BEEB.MMB file but just the same. If I type LIST it replies Card?
So I wonder if the microSD card slot is not working - how to check?

Tony

[ken.boak]

Tony,

The signals to the uSD card are shared with the slide switches.

Make sure that all slide switches are in the OFF position - that way you should be able to read the uSD.

Ken

[BigEd]

For best chance of success, the card should be newly formatted with just the BEEB.MMB file on it - AIUI the ROM doesn't have any code to understand large catalogues, subdirectories, or fragmented files.

[tony1tf]

Yes, the slide switches are "up" and I have reformatted the card, but still no joy. Sometimes I get garbage on the screen when trying to boot into MMFS as shown here:

[ken.boak]

Tony,

Slide switches should be all "down" - OFF in other words - perhaps we are at cross purposes?

Ken

[tony1tf]

Wow - it works - I saw that the up position said ON, but for some reason I thought that was not being pulled down by the switches. Mind you, I tried them in both positions earlier, but perhaps I have "cleaned" the filing system since.

Tony

[tony1tf]

I've got some weird colour mapping - here is a picture of the Elite start-up screen - strangely most of the colours look the same as Dave's on this photo taken with my phone, but when I look at my VGA screen, the top part is OK, but the bottom part shows purple instead of white, red instead of orange and dark blue instead of light blue. Changing the brightness and contrast on the monitor doesn't make any difference. It must be flickering at a rate that makes the photograph different from my eyes.

Tony