RetroBSD
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SDRAM based board - a prototype run - any interest on it?
http://retrobsd.org/viewtopic.php?f=3&t=5004
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Author:  Pito [ Mon Nov 26, 2012 6:08 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Or let it be - do not break SPI out from the buffer side - rather from pic32...

Author:  jaromir [ Tue Nov 27, 2012 1:18 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

So, I spent solid few hours managing how to get few resistors on board. Now I'm really fed up with board changes and after final polishing the board will go into production. I'll look at pin labeling before submitting.
The schematics looks fugly, especially around SD part - result of late night edits. I'll fix it. On bottom part is new 4-pin connector with SPi signals. I'm not sure, whether cut some GPIO signals from bottom connector and route it there or leave it as it is.
i would vote for leaving it there - if somebody is interested, he can drill out three vias and greenwire SPI connections to bottom connectors.
SPI connector is in 2,54mm module with respect to main bottom connector.

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Author:  jaromir [ Tue Nov 27, 2012 2:09 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

wiz: CadSoft changed file formats when going from 5.x version to 6.x version. So, files processed in eagle 5 are compatible with both 5 and 6 versions, but files from version 6 are not possible to open in version 5.
I'm keeping with version 5.1, as it is very stable and usable version, with no apparent bugs for me and I'm pretty used to it. They made also few interface changes in Eagle 6 and honestly I have no reason to migrate to 6.

Eagle is free to use for non-commercial projects in its free version. It has only limitation to board size 80*100mm, no other crippling features.
Otherwise, full version is relatively cheap.

I'll download linux of Eagle version to verify my board/schematics.

My email address is jaromir {dot} sukuba {at} gmail {dot} com

Author:  Pito [ Tue Nov 27, 2012 2:29 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

@jaromir - this is maybe not a joke - I think we need a discharge resistors (ie 10k) on vccsd1 and vccsd2 against GND. When we switch off the sdcards with pmofsets it may happen the cards (and their pullups) will be powered log1 from caps for a while (??msecs/secs) because they are in idle (it depends in their idle current).
Another option is to wait long enough before tampering the cards..
PS: I would put it there, frankly, otherwise a pic32 driven off/on restart of the cards may now work properly..

Author:  jaromir [ Tue Nov 27, 2012 2:43 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Yes, you are probably right... two more resistors... in that crowded area... :evil:

Author:  Pito [ Tue Nov 27, 2012 2:45 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

You may still consider 0402 :P

Author:  Pito [ Tue Nov 27, 2012 3:03 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

..and the 244 needs very good decoupling - 10u + 100n.

Author:  jaromir [ Tue Nov 27, 2012 3:17 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

There is single 0805 cap for 244. I feel like single 100nF would be enough, but i added another cap position - for 10uF - to be sure.

I cleaned up layers for top and bottom silkscreen.

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File comment: bottom
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Author:  Pito [ Tue Nov 27, 2012 3:29 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

The rear connector - it is clear we cannot put description there - but it would be good to have at least rows and columns numbered - like a chessboard or something like that...
And do check it with gerbview before sending it out.. ;)

Author:  wiz [ Tue Nov 27, 2012 4:04 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Hi Jaromir,

WOW :) ! Great job. Time to print :). Boy do I remember those days.

Can't wait to see it running :).

I'll e-mail you my e-mail. It would be fun to see if I can bring up your stuff with 5.11.

We could take bets as to how many "I told you so's" we will have in the log after the PCB is printed. I look at these as volunteers for doing the next revision :).

Wiz

Author:  jaromir [ Wed Nov 28, 2012 8:28 am ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

I made some cosmetic changes, added bottom connector numbering (for both top and bottom layer) and I'll let it be at least one day before submitting to factory.

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Author:  Pito [ Wed Nov 28, 2012 8:31 am ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Nice, if possible, pls put the description of the rear bus on the bottom silk as well..
Good luck!

Author:  jaromir [ Wed Nov 28, 2012 12:16 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

It was already there. You can't surprise me! :mrgreen:

Author:  jaromir [ Mon Dec 03, 2012 11:47 am ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Well,
gerber data were checked and sent to manufacturer. Now I have to wait.

Author:  Pito [ Mon Dec 03, 2012 12:06 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Red mask? :D
So a lot of work during Xmas..

Author:  jaromir [ Mon Dec 03, 2012 2:15 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

no, traditional ugly and boring green mask... though cheaper :)

Author:  majenko [ Mon Dec 03, 2012 9:53 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

What are your mounting hole centres / sizes? I am making a VGA board on 5x5 from iTead, and I'd like to get the mounting holes the same.

BTW, I'm interested in one of these when they're done :)

Oh, and is there any chance of a pinout table for the 15x3 connector?

Here's my (work in progress) VGA board:
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Author:  Pito [ Mon Dec 03, 2012 10:44 pm ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Quote:
for the 15x3 connector

That is RetroBus v1.0 ... :)
I think we need 2.0 to become an established standard. I am still missing a complete 8 or 16b bus there.. And probably we will miss few signals there..
February 2013 - RetroBus v 2.0

This is a prototype run - my expectation would be the RetroBoard v1.0 (current) will prove rock stability with sdram and two sdcards (with power on/off), i2c RTC driver running, etc. Quite a lot work around the Xmas..
Jaromir is certainly filling in the questionnaire on the RBus 1.0 already ;)

PS: while waiting on the pcbs we may:
1. create a retroboard-sdramp-uart board (in the merged trunk preferably)
2. create an i2c driver
3. create an RTC driver
4. upgrade the rd_sd to rd_sdpw for the powering on/off
5. create test cases for testing of the sdram, sdcards, the rtc
6. implement fat32 driver for the sdcard2 :)
7. implement a root filesystem on the sdram (FOS)


.. and boards will arrive in ~3 weeks.. :shock:

Author:  majenko [ Tue Dec 04, 2012 12:35 am ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

Pito wrote:
PS: while waiting on the pcbs we may:
1. create a retroboard-sdramp-uart board (in the merged trunk preferably)
2. create an i2c driver
3. create an RTC driver
4. upgrade the rd_sd to rd_sdpw for the powering on/off
5. create test cases for testing of the sdram, sdcards, the rtc
6. implement fat32 driver for the sdcard2 :)
7. implement a root filesystem on the sdram (FOS)


.. and boards will arrive in ~3 weeks.. :shock:


Is the RTC internal or external? From what I recall of the rest of the thread (I haven't been watching it that closely) it's external... :( If it were the internal RTCC of the PIC32 I already have a ChipKit library for it that'd be simple enough to port... That said, the internal RTCC is pretty pointless without a proper backup power input to the chip...

I have plans for the I²C interface, but I don't yet quite know how I'm going to make it work ;)

The version of rd_sd.c that was re-jiggered for the spi_bus driver should support power on both cards already. I haven't been able to test it (no power controlled cards), but the code is largely what was there already - just expanded for more than one card. (I think. If not, it's easy to expand it. I was planning to do it, but I can't remember off hand if I did or not).

And FAT32 would be simplest to implement as a set of userland utilities (i.e., port mtools or similar) - that way we don't have to add extra overhead for more mount points, re-write the entire kernel to support multiple filesystems, and generally overload the system with bloat.

Author:  Pito [ Tue Dec 04, 2012 1:11 am ]
Post subject:  Re: SDRAM based board - a prototype run - any interest on it

The RTC is an external I2C (PCF8563, 200nA) with a battery backup (CR1220) on the board.
The driver for that RTC is basically the same as for the DS1307 (the register's sequence differ a little bit). Drivers are available.
http://arduino.cc/playground/Main/RTC-PCF8563

What is needed is the I2C driver..
http://www.linuxjournal.com/article/7136?page=0,0

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