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GlennSmith
PostPosted: Mon Jun 12, 2023 7:08 am 
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Joined: Thu Dec 26, 2002 12:29 pm
Posts: 81
Location: Occitanie, France
Hello all,
My design for my new WorkBench Computer (WBC) is coming along slowly, and I have decided that I really want to offload the CPU and VIA(s) as much as possible from doing bit-banging donkeywork. Dedicated chips exist for doing I2C interfacing (the newer generation devices, like the PCA9663/65 are, on paper, really impressive), but nothing really exists for SPI. As I've some experience with PICs and AVRs I decided to create a challenge and create my own SPI interface device around a PIC24F device. It turned-out that the DIP28 version of the chip I was looking at didn't have enough pins to be useful - so I doubled the challenge to use the 44-pin SMT version.
The H/W design is at a fairly complete phase. The device has an 8-bit // interface for the 6502 side of things, and I am pushing for SPI, I2C and TTL-level "RS232". The firmware in the PIC is yet to be designed - that's the 2nd-next step.
The board is currently laid-out in 80mm x 50mm. Rs and Cs are oversized 'cos I wanted the board to be - with some experience/effort - home solderable. It looks something like the picture below.
So, here's the idea : if anyone else is interested in this idea can they give me a heads-up and I'll gladly share/cooperate. Any feedback on my design is also welcome.
More news soon...
Glenn-in-France


Attachments:
File comment: The schematic
PIC24F_Breakout.pdf [467.1 KiB]
Downloaded 51 times
File comment: The board
PIC24F_Breakout_3D.jpg
PIC24F_Breakout_3D.jpg [ 79.22 KiB | Viewed 732 times ]


Last edited by GlennSmith on Mon Jun 12, 2023 5:51 pm, edited 1 time in total.
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GARTHWILSON
PostPosted: Mon Jun 12, 2023 7:41 am 
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GlennSmith wrote:
, but nothing really exists for SPI.

Well, this could be a good-news/bad-news thing:  There is a 65SPI chip from Daryl (forum name "8BIT") made with a CPLD, at https://sbc.rictor.org/65spi2.html .  Unfortunately he is not providing programmed parts (or at least wasn't, the last I checked), but he provides the source code and object code to program the Atmel ATF1504 CPLD.  So there is a 6502-bus-compatible chip that takes care of everything so you don't have to bit-bang.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
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GlennSmith
PostPosted: Mon Jun 12, 2023 7:51 am 
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Location: Occitanie, France
GARTHWILSON wrote:
GlennSmith wrote:
, but nothing really exists for SPI.

Well, this could be a good-news/bad-news thing:  There is a 65SPI chip from Daryl (forum name "8BIT") made with a CPLD, at https://sbc.rictor.org/65spi2.html .  Unfortunately he is not providing programmed parts (or at least wasn't, the last I checked), but he provides the source code and object code to program the Atmel ATF1504 CPLD.  So there is a 6502-bus-compatible chip that takes care of everything so you don't have to bit-bang.

Hi Garth, you're an early bird! I had seen and analysed Daryl's device, but unfortunately CPLD is where I don't want to go - I think I've got my head around enough different technologies for one life. I want to be able to move ahead with the toolkit I have. That said, I had vowed not to go down SMT road : but the chip mfrs have forced me...
I am basing my design spec around Daryl's feature list, however. I've limited the board to 4 SPI client selects for the moment for real estate reasons, but I could go to 8nif I change my sockets. Thanks for the feedback.
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GARTHWILSON
PostPosted: Mon Jun 12, 2023 7:56 am 
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I'm a late bird.  :lol:   I'm on the west coast of the US, and I am almost never in bed before 2am.

Maybe you could persuade him (or even someone else) to program a batch of parts to sell, and then you could have the ready-made chip without having to get into programming CPLDs yourself.  You'd just receive it in the mail and install it on your board, as if it were not a CPLD at all.

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The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?
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BigDumbDinosaur
PostPosted: Mon Jun 12, 2023 5:10 pm 
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GlennSmith wrote:
My design for my new WorkBench Computer (WBC) is coming along slowly...

Another unreadable schematic. <sigh> All I see is an empty rectangle and some bits-and-pieces with nothing to tell me what they are.

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GlennSmith
PostPosted: Mon Jun 12, 2023 5:27 pm 
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Location: Occitanie, France
BigDumbDinosaur wrote:
Another unreadable schematic. <sigh> All I see is an empty rectangle and some bits-and-pieces with nothing to tell me what they are.

PDF updated for B/W schematic.

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