Acorn "POST box" display adaptor (0086,804)

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Re: Acorn "POST box" display adaptor (0086,804)

Post by philpem » Thu May 21, 2020 12:24 am

I picked up the parts to make a permanent version of my display-only (or possibly display + FT245R) variant this week. I'm planning to use an XC9572XL, the LCD display, and a few line drivers for the host interface.

I have somewhat modest goals! :)

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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Thu May 21, 2020 6:54 am

philpem wrote:
Thu May 21, 2020 12:24 am
I picked up the parts to make a permanent version of my display-only (or possibly display + FT245R) variant this week. I'm planning to use an XC9572XL, the LCD display, and a few line drivers for the host interface.

I have somewhat modest goals! :)
I’ve laid out a PCB in KiCad for this and it fits neatly on an 85x42mm board with the LCD on one side and the CPLD on the other.

I’ll report back when I have something working. Min order is 5 boards so I’ll likely have some spares.

I notice Seeed Studio has the CPLD breakouts in stock if you want to go that route.
CDDFE6C6-1555-4743-8FE0-D4A589B9D59B.jpeg

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Re: Acorn "POST box" display adaptor (0086,804)

Post by Kazzie » Thu May 21, 2020 7:38 am

anightin wrote:
Thu May 21, 2020 6:54 am
I’ve laid out a PCB in KiCad for this and it fits neatly on an 85x42mm board with the LCD on one side and the CPLD on the other.

I’ll report back when I have something working. Min order is 5 boards so I’ll likely have some spares.
I'd be interested in one of those spare boards, as once we're free to travel, I'll have four 32-bit Acorns to collect and repair. :)
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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Thu May 21, 2020 8:58 am

Kazzie wrote:
Thu May 21, 2020 7:38 am
anightin wrote:
Thu May 21, 2020 6:54 am
I’ve laid out a PCB in KiCad for this and it fits neatly on an 85x42mm board with the LCD on one side and the CPLD on the other.

I’ll report back when I have something working. Min order is 5 boards so I’ll likely have some spares.
I'd be interested in one of those spare boards, as once we're free to travel, I'll have four 32-bit Acorns to collect and repair. :)
No problem Kazzie, I'll set one aside for you. I haven't sent off for the boards yet as I want to do some final checks today then put in my order -- usually takes about 2 weeks.

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Re: Acorn "POST box" display adaptor (0086,804)

Post by philpem » Thu May 21, 2020 2:00 pm

anightin wrote:
Thu May 21, 2020 6:54 am
I’ve laid out a PCB in KiCad for this and it fits neatly on an 85x42mm board with the LCD on one side and the CPLD on the other.

I’ll report back when I have something working. Min order is 5 boards so I’ll likely have some spares.

I notice Seeed Studio has the CPLD breakouts in stock if you want to go that route.

CDDFE6C6-1555-4743-8FE0-D4A589B9D59B.jpeg
Nifty!

I was thinking of using a TTL oscillator to save having the 74LS04, caps and crystal sticking up off the board.

Can your board connect up to a host computer to allow the memory read/write commands (Probe module type features) to be used?

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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Thu May 21, 2020 4:03 pm

philpem wrote:
Thu May 21, 2020 2:00 pm
anightin wrote:
Thu May 21, 2020 6:54 am
I’ve laid out a PCB in KiCad for this and it fits neatly on an 85x42mm board with the LCD on one side and the CPLD on the other.

I’ll report back when I have something working. Min order is 5 boards so I’ll likely have some spares.

I notice Seeed Studio has the CPLD breakouts in stock if you want to go that route.

CDDFE6C6-1555-4743-8FE0-D4A589B9D59B.jpeg
Nifty!

I was thinking of using a TTL oscillator to save having the 74LS04, caps and crystal sticking up off the board.

Can your board connect up to a host computer to allow the memory read/write commands (Probe module type features) to be used?
I just built this up from stuff I readily had lying around and it matches the working breadboard.

In it's present form it simply reads the status and drives the LCD so there is scope for reprogramming the CPLD at some point to access TESTREQ and TESTACK as required, then feeding to the host via an Arduino or similar -- plenty of spare IO on the breakout board for this.

I'm still learning at this so one step at a time :D

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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Fri May 22, 2020 6:59 pm

Talking of memory access commands... does anyone have any good ideas for things to do there? It looks like it should be possible to write whatever we like into memory then execute it, although my current hardware isn’t reliable enough to pull that off. I wonder if it would work to start executing RISC OS from just after the self test, so that it didn’t overwrite memory contents — then you might be able to have it start up with a RAM disk.
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Re: Acorn "POST box" display adaptor (0086,804)

Post by philpem » Fri May 22, 2020 8:08 pm

myelin wrote:
Fri May 22, 2020 6:59 pm
Talking of memory access commands... does anyone have any good ideas for things to do there? It looks like it should be possible to write whatever we like into memory then execute it, although my current hardware isn’t reliable enough to pull that off. I wonder if it would work to start executing RISC OS from just after the self test, so that it didn’t overwrite memory contents — then you might be able to have it start up with a RAM disk.
I was thinking hardware tests. If you've got IOMD issues (for example), you can poke the registers and see what comes back.

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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Sat May 23, 2020 9:38 pm

Yeah, that’s definitely a good one. I started on that in the firmware on my fork before giving up on fixing the A5000; didn’t get that far though as the results just seemed to show that IOEB wasn’t responding at all, so there wasn’t much to go on :(
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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Wed May 27, 2020 7:51 am

Only about halfway there, and the traces look terrible, but it just passed DRC, so here's a first cut up on Github: https://github.com/google/myelin-acorn- ... st_box_usb
pcb-front.png
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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Wed May 27, 2020 2:57 pm

myelin wrote:
Wed May 27, 2020 7:51 am
Only about halfway there, and the traces look terrible, but it just passed DRC, so here's a first cut up on Github: https://github.com/google/myelin-acorn- ... st_box_usb

pcb-front.png
Looks like this is shaping up to be the ultimate POST box upgrade, nice work :D

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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Wed May 27, 2020 8:25 pm

Fingers crossed! The main goal here is to make a POST box that's hot swap capable and a bit overpowered so it doesn't depend on any hacks like running the MCU in SPI slave mode, but I've also never used any Lattice FPGAs, so I wanted a breakout board that I can use to mess around with them. That's what the 40-pin header along the bottom is for; it brings out 34 FPGA IOs (then the vertical header brings out all the MCU's GPIOs). So hopefully this should be useful for other things too...
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Re: Acorn "POST box" display adaptor (0086,804)

Post by Kazzie » Wed May 27, 2020 9:20 pm

I've not played around with FPGAs for a decade or so, since a brief flirt with them at university. That LCMXO256 looks to have a far denser pinout than anything I've surface mounted too, so that'll be an added challenge. (It's helped me justify buying some fine chisel tips for my soldering iron, if nothing else. :) )
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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Wed May 27, 2020 9:51 pm

The 0.5mm pin spacing is a pain; unfortunately FPGAs don't tend to be in hobbyist-friendly packages :( At least this one is hand solderable and reworkable, unlike the BGAs I've been using in my other projects, but I still don't have 100% success soldering 0.5mm QFP. I haven't had any complete failures (misaligned chips, broken pins) since getting a decent magnifier (a Donegan OptiVISOR DA-4), but make sure you have a flux pen, some solder braid, and the finest iron tip you can find -- I use a Weller ETS (1/64" or 0.38mm) with my WES51 iron.
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Re: Acorn "POST box" display adaptor (0086,804)

Post by philpem » Fri May 29, 2020 11:46 am

I've had good success soldering fine-pitch QFPs using drag-hoof (Miniwave) soldering tips, thin solder (0.3 or 0.5mm) and lots of flux.

The key is the paste flux. Take a look at a Louis Rossman laptop repair video and see how much he uses -- that's a good baseline :)

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Re: Acorn "POST box" display adaptor (0086,804)

Post by Kazzie » Fri May 29, 2020 3:35 pm

Thanks for the advice. Just arrived today are a set of what I'd have called bevel tips, but it seems that others call them hoof-shape. The finest is 1mm:
IMG_20200529_1530377.jpg
1mm, 2.3mm, 3mm tips for Antex M12
I've already got a reel of 0.5mm leaded solder that I bought in anticipation of working on the lockdown-delayed Archimedes/Risc machines. My flux is in paste form rather than pen form, but I've got plenty of it. :)
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Re: Acorn "POST box" display adaptor (0086,804)

Post by philpem » Fri May 29, 2020 4:08 pm

Kazzie wrote:
Fri May 29, 2020 3:35 pm
Thanks for the advice. Just arrived today are a set of what I'd have called bevel tips, but it seems that others call them hoof-shape. The finest is 1mm:IMG_20200529_1530377.jpg
They look like Antex tips - which means they're probably chisel bits. Unless Antex has widened their product range recently, that is (or they're not Antex bits at all)!

Drag-hoof is Metcal's name for them. MiniWave is Pace's (trademarked!) name, which alludes to how they work. A small bead of solder which behaves like a massively scaled down version of a wave-soldering machine.

The giveaway is that a hoof / mini-wave tip will have a slightly concave face. Chisel tips are flat.
You might have to put a metal ruler against it to be able to see the concave section.

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Re: Acorn "POST box" display adaptor (0086,804)

Post by danielj » Fri May 29, 2020 4:35 pm

I just use a 2mm bevel bit for drag soldering, and regularly do 0.5mm (those stm32s) - line up tacking a corner pin, drag opposite side then the rest, plenty of flux (I use very liquid stuff), then clean up any bridges with braid...

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Re: Acorn "POST box" display adaptor (0086,804)

Post by Kazzie » Fri May 29, 2020 4:55 pm

philpem wrote:
Fri May 29, 2020 4:08 pm
Kazzie wrote:
Fri May 29, 2020 3:35 pm
Thanks for the advice. Just arrived today are a set of what I'd have called bevel tips, but it seems that others call them hoof-shape. The finest is 1mm:IMG_20200529_1530377.jpg
They look like Antex tips - which means they're probably chisel bits. Unless Antex has widened their product range recently, that is (or they're not Antex bits at all)!

Drag-hoof is Metcal's name for them. MiniWave is Pace's (trademarked!) name, which alludes to how they work. A small bead of solder which behaves like a massively scaled down version of a wave-soldering machine.

The giveaway is that a hoof / mini-wave tip will have a slightly concave face. Chisel tips are flat.
You might have to put a metal ruler against it to be able to see the concave section.
They are indeed Antex (as the image caption noted), and they're flat faced from what I can see. A concave face would make the name "hoof" a lot more sensible!
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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Mon Jun 01, 2020 3:42 pm

Just received my PCBs today as per earlier post, built one up to check they were okay:
IMG_7021.jpeg
IMG_7026.jpeg
IMG_7027.jpeg
I realise this is the 'simple' version that just outputs POST data to the LCD, but it should be good for board bring up tests pending @Myelin's interactive version.

I have 3 spare as min order was 5. I have one CPLD breakout spare I can supply with the board.

Update schematic showing parts needed:

ACORN_POST_Reader.pdf
(86.68 KiB) Downloaded 11 times
Last edited by anightin on Mon Jun 01, 2020 4:34 pm, edited 2 times in total.

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Re: Acorn "POST box" display adaptor (0086,804)

Post by Kazzie » Mon Jun 01, 2020 4:04 pm

anightin wrote:
Mon Jun 01, 2020 3:42 pm
I have 3 spare as min order was 5. @Kazzie do you still want one of these?
Yes please. :D

I'd also appreicate a BOM, so I can order in what I'll need to assemble it.
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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Mon Jun 01, 2020 4:12 pm

Kazzie wrote:
Mon Jun 01, 2020 4:04 pm
anightin wrote:
Mon Jun 01, 2020 3:42 pm
I have 3 spare as min order was 5. @Kazzie do you still want one of these?
Yes please. :D

I'd also appreicate a BOM, so I can order in what I'll need to assemble it.
Sure, I'll post a pdf of the schematic when I get access to my work laptop later. I also have a couple of spare CPLD breakout boards (populated). I can include one of these with the PCB (both at cost + P&P). The POST assembly took about 10-15 mins to make. PM me with you address and I'll post something later this week.

Update:
PDF of schematic added to my POST

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Re: Acorn "POST box" display adaptor (0086,804)

Post by Kazzie » Mon Jun 01, 2020 4:30 pm

anightin wrote:
Mon Jun 01, 2020 4:12 pm
Sure, I'll post a pdf of the schematic when I get access to my work laptop later. I also have a couple of spare CPLD breakout boards (populated). I can include one of these with the PCB (both at cost + P&P). The POST assembly took about 10-15 mins to make. PM me with you address and I'll post something later this week.

Update:
PDF of schematic added to my POST
A ready-built breakout board would be great, thanks. PM sent.
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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Tue Jun 02, 2020 7:21 am

Nice work Andy!

It looks like JLC is about to put my boards in the mail, so with any luck I'll be able to give them a try next week sometime. I'm pretty happy with the Verilog now (post_box_usb.v and postcode.v) and have gotten the firmware for the MCU to compile. Fingers crossed!
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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Tue Jun 02, 2020 9:09 am

myelin wrote:
Tue Jun 02, 2020 7:21 am
Nice work Andy!

It looks like JLC is about to put my boards in the mail, so with any luck I'll be able to give them a try next week sometime. I'm pretty happy with the Verilog now (post_box_usb.v and postcode.v) and have gotten the firmware for the MCU to compile. Fingers crossed!
Excellent stuff, looking forward to seeing it come together!

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Re: Acorn "POST box" display adaptor (0086,804)

Post by danielj » Tue Jun 02, 2020 10:08 am

anightin wrote:
Mon Jun 01, 2020 3:42 pm

I have 3 spare as min order was 5. I have one CPLD breakout spare I can supply with the board.
Ooh, do you have any still?

d.

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Re: Acorn "POST box" display adaptor (0086,804)

Post by philpem » Tue Jun 02, 2020 10:22 am

myelin wrote:
Tue Jun 02, 2020 7:21 am
Nice work Andy!

It looks like JLC is about to put my boards in the mail, so with any luck I'll be able to give them a try next week sometime. I'm pretty happy with the Verilog now (post_box_usb.v and postcode.v) and have gotten the firmware for the MCU to compile. Fingers crossed!
Let me know if you've got any spare PCBs - having looked at the firmware, I'm leaning more towards building one of yours than doing a PCB for my CPLD + FTDI + LCD version.

Cheers!
Phil

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Re: Acorn "POST box" display adaptor (0086,804)

Post by sP1d3r » Tue Jun 02, 2020 10:24 am

:o Hi

I thought it might interest you to see a small soldering practice kit I've got, it has 0.5mm pitch contacts as well as 1mm pitch.
They are cheap to buy on eBay etc., you can gain some useful experience of soldering.
There's no SSOP28 included, you'd have to buy a suitable one also.
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WP_20200601_23_33_32_Pro (2).jpg
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Re: Acorn "POST box" display adaptor (0086,804)

Post by anightin » Tue Jun 02, 2020 11:05 am

danielj wrote:
Tue Jun 02, 2020 10:08 am
anightin wrote:
Mon Jun 01, 2020 3:42 pm

I have 3 spare as min order was 5. I have one CPLD breakout spare I can supply with the board.
Ooh, do you have any still?

d.
Sure, PM me your address and we can sort postage :)

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Re: Acorn "POST box" display adaptor (0086,804)

Post by myelin » Tue Jun 02, 2020 10:57 pm

philpem wrote:
Tue Jun 02, 2020 10:22 am
Let me know if you've got any spare PCBs - having looked at the firmware, I'm leaning more towards building one of yours than doing a PCB for my CPLD + FTDI + LCD version.
Yes, absolutely; I did an order for 10, so assuming it works, I'll have plenty of spares! Guess I should go place the Digikey order so I actually have all the bits :)

Update: they arrived! Beat the Digikey order for sure; it's still a few days off.
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