My way for 6502 communications, UART & SPI/I2C

[maurice6502]

Hi,
a little contribution to this supertech community, my personal solution to ACIA and I2C/SPI with 65C02.
It's a DIL28 stamp circuit, 65C51 pinout compatible with following resources:

- one AtMega328PB microprocessor, running at 18.432 Mhz
- one 8 bit latch written from 65C02 , as data register for TX operation
- one 8 bit latch written from AtMega328 , as data register for RX operation
- some logic to allow 65C02 IRQ or NMI operations or polled operation
- one RS232 port of AtMega328 on native pins of 65C51 (pin 10 and 12)
- one further RS232 port of AtMega328 on pins normaly connected to level traslator as RTS/CTS (pin 8 and 9); alternatively should be used as part of SPI connection
- one I2C port of AtMega328 wired on pins 7 and 11

Local AtMega should be used to process communications service as coprocessor..
Enclosed EAGLE files (compatible with free version) and picture of board.

[maurice6502]

Here Eagle files

[gfoot]

Very nice indeed! And welcome

[fachat]

Very nice! I'll have a look as I am investigating a method to connect an atmel avr to a 6502 bus. We may have had the same ideas.

Can you attach screenshots of the schematics as well? I do have eagle, but not really handy eg on my phone now!

Thanks
André

[maurice6502]

fachat wrote:

Very nice! I'll have a look as I am investigating a method to connect an atmel avr to a 6502 bus. We may have had the same ideas.

Can you attach screenshots of the schematics as well? I do have eagle, but not really handy eg on my phone now!

Thanks
André

André,
attachment of first post is in pdf format, let me know if you are able to read it.

[Michael]

The 6551 (faux) pinout is nice. Have you implemented serial buffers by any chance?

[BigDumbDinosaur]

Please do not do schematics in color.  There are certain color combinations that are unreadable for me.

[Michael]

BigDumbDinosaur wrote:

Please do not do schematics in color.  There are certain color combinations that are unreadable for me.

Please bookmark; Convert Color to Greyscale

[GARTHWILSON]

Michael wrote:

BigDumbDinosaur wrote:

Please do not do schematics in color.  There are certain color combinations that are unreadable for me.

Please bookmark; Convert Color to Greyscale

What would be interesting and helpful would be if there were a way to apply different color filters like we used to put on camera lenses for B&W photography back in the days of film.  For example, a yellow filter would make clouds stand out more against a blue sky, orange all the more, and a red filter would put bright, puffy clouds against a nearly black sky, whereas a blue filter would nearly make the clouds disappear.  A green filter would brighten foliage.  If the software gave sliders so you could see the results immediately, yellow and light green could for example get separated out instead of both turned to the same shade of gray.  This could be done in Gimp or Photoshop, but it just takes time.  Otherwise it'd probably be best to turn anything that's not white into black.

I've asked Eagle repeatedly to change the default colors in their CAD, but I guess they don't care.  (Now I see Eagle is going down; but I guess KiCad is doing it too.)

[fachat]

maurice6502 wrote:

fachat wrote:

Very nice! I'll have a look as I am investigating a method to connect an atmel avr to a 6502 bus. We may have had the same ideas.

Can you attach screenshots of the schematics as well? I do have eagle, but not really handy eg on my phone now!

Thanks
André

André,
attachment of first post is in pdf format, let me know if you are able to read it.

Thanks I only saw the image not the pdf.

Why are you useing '373 latches?

I either use '273 - which are to my knowledge the only ones with /RES or '374/'574 (IIRC) registers. I know chances are very low but latches like the '373 can change while 'open' which can lead to potentially inconsistent values.
Again, chances are low but I like to look at such details

Thanks again for sharing!

André

[pjdennis]

Michael wrote:

BigDumbDinosaur wrote:

Please do not do schematics in color.  There are certain color combinations that are unreadable for me.

Please bookmark; Convert Color to Greyscale

This works, but it's kind of a pain to download the image, upload it to the converter, download the converted image and then view it.

As an alternative I've used this chrome extension (also works on Edge) which adds a key shortcut to render the current web page in greyscale. Other browsers might have a similar option available.

Also, Windows (10 and above) has "Color Filters" (under "Ease of Access") which can apply greyscale to the entire desktop, again via a shortcut. Other OS's might have a similar capability.

[Dr Jefyll]

It's also quite easy to download the image then remove the color by means of photo editing software.

GIMP, Photoshop and Paint Shop Pro come to mind, but even a comparatively rudimentary package should suffice. The menu selections will surely include several pertaining to color, and it's only necessary to find the "Saturation" setting and reduce it to the minimum value; this will yield a gray-scale rendition.

I sometimes do this myself, simply because I don't find the color helpful. After one has grown familiar with where menu selections are located, the process can be done in seconds and without assistance from others.

-- Jeff

[barnacle]

With all respect to BDD, there are plenty of cases where including colour in an image provides either aesthetic or semantic improvement; it seems a shame that this information might be lost, reducing the utility for the majority, to help one viewer. I'm no CSS expert, but I wonder if there might be something which can be done client-side at the browser using CSS? Certainly conversion to grayscale is simple, and indeed one might use different conversion factors (other than the standard Y= 0.3R + 0.59G + 0.11B) to emphasise or otherwise various colours.

That said, as a courtesy I now post all my circuit diagrams in monochrome: in Kicad that's simple - plot the schematic to pdf, and select monochrome rather than colour in the drop-down. I haven't found a useful way to make a similar output of a PCB though; they tend to use a lot of ink if I print them due to the black background...

Neil

ps: when I started work at the BBC in the seventies, there were still significant numbers of monochrome receivers around, so every studio had both monochrome and colour output displays so the director could check the picture remained acceptable on both. But equally I have argued long and hard - and lost the argument on cost grounds - about using bi-colour green/red LEDs to indicate state changes on some designs. Annoying, given that red-green colour blindness is the most common...

[speculatrix]

barnacle wrote:

Annoying, given that red-green colour blindness is the most common...

I have a colour-blind friend who has the same feeling about traffic lights. Especially those strung above the road where positional clues may be missing.

[BigEd]

Yes, I'm pretty sure a bookmarklet, if not a browser mode or OS accessibility feature, could render any page or image in increased contrast, greyscale, inverse brightness, or any other simple colour space conversion. I'm not motivated to find one or write one, but if in BDD's shoes I'm sure I would.

(I'm generally in favour of accessibility features and accommodations, of course. Sometimes the onus is on the writer, sometimes the publisher, sometimes the reader.)