RetroBSD

2.11BSD operating system for microcontrollers
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 Post subject: SDZL board schematics
PostPosted: Wed Mar 04, 2015 1:03 pm 

Joined: Mon Nov 24, 2014 1:07 pm
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Hi,

Are there any board schematics around for Majenko's (Matt's) SDZL board? I'd like to get things ready to make my own custom version, ie pcb design, use parts I already have in my collection etc.

Thanks,

Dan


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PostPosted: Wed Mar 04, 2015 1:40 pm 
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Not yet, no. It's still in the process of being designed / redesigned / broken / repaired, etc.

It's loosely based around the Fubarino SD schematics, but with a 64-pin MZ chip and tweaked power systems.

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PostPosted: Wed Mar 04, 2015 3:28 pm 

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Hi Matt,

Thanks for the reply! I think I'll have a go at doing my own variant as I did with the Fubarino SD unless you beat me to it, but only once I've finished the i2c driver. Getting there but very slowly :/

Many Thanks,

Dan


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PostPosted: Wed Mar 04, 2015 3:47 pm 
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Hi Dan,

COUNT ME IN !!!!!!!

Maybe an MX and an MZ version with the same interface pinout ?

Wiz


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PostPosted: Thu Mar 05, 2015 3:23 am 
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How about SDZL variant with Ethernet RJ45 socket on one side?
It would be a unique product, like `networked BSD for your breadboard'. :)

I'm almost done with Ethernet driver for LiteBSD.


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PostPosted: Thu Mar 05, 2015 10:16 am 
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You mean maybe replace the USB port (currently useless) with a PHY and Magjack?

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PostPosted: Thu Mar 05, 2015 11:57 am 
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Hmm, do you think the wires are trendy? I doubt so :P

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PostPosted: Thu Mar 05, 2015 2:00 pm 
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Hi Serge and Dan and all,

GREAT NEWS SERGE :) :).

Yup. Real networked RetroBSD, LiteBSD or whatever.

Forget USB. Use real open ethernet that works without the license sauce!. With real Unix applications that don't feature the Microsoft or Google sauce.

Most Exciting !!

Wiz


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PostPosted: Thu Mar 05, 2015 7:24 pm 
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majenko wrote:
You mean maybe replace the USB port (currently useless) with a PHY and Magjack?

No, I mean: leave USB port as is (we will eventually develop a USB stack for LiteBSD) and put microSD underneath it. Put Magjack on the opposite side. Microchip 8720A board is a good example of layout. It leaves little space for LEDs and buttons though: should be moved elsewhere.


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PostPosted: Thu Mar 05, 2015 8:25 pm 
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Hmmm, could be tricky to fit actually. The SD card may interfere with the body of the USB plug. Might be better to have the SD card and the Ethernet connector at the same end. Would need SMD Magjack of course...

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PostPosted: Thu Mar 05, 2015 8:51 pm 
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majenko wrote:
The SD card may interfere with the body of the USB plug.

I doubt it would interfere. The SD csrd socket has a metal enclosure, and internal ground layer of the PCB provides an additional shielding.

Microchip uses J3011G21DNL for Ethernet connector.

It may have sense to throw out USB and replace it by, say, CP2102 connected to UART port.


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PostPosted: Thu Mar 05, 2015 8:54 pm 
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I mean physically, not electrically. Not enough room to insert or eject the card while the USB cable is plugged in.

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PostPosted: Thu Mar 05, 2015 9:27 pm 
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Oh yes, physically when USB cable connected, it will prevent to eject microSD card. But that's probably not a big issue. Anyway the kernel does not allow to detach a swap partition while the system is up and running.


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PostPosted: Thu Mar 05, 2015 9:38 pm 
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By putting the Ethernet and SD at the same end it would allow you to eject the SD. The Ethernet doesn't have the same size problems as the USB.

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PostPosted: Thu Mar 05, 2015 9:44 pm 
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In this case it's not possible to use the space underneath Magjack for PHY chip and the harness. Probably no big deal, though.


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PostPosted: Thu Mar 05, 2015 10:03 pm 
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The PHY chip is only little. It'll go behind the Magjack fine I would have thought. Little QFN normally.

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PostPosted: Fri Mar 06, 2015 12:31 pm 
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With having the PHY in there you'd have less IO ports available to the headers, so there's going to be less IO pins. Probably the whole area where the Magjack would be is going to be devoid of IO pins. The headers won't be the same as the Fubarino SD then. No matter. The whole board layout may change then to make it something completely different. Still keep it breadboard compatible, but no longer the same pinout as a FuSD. Maybe not even rectangular...

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PostPosted: Mon Mar 09, 2015 9:16 am 

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Hi All,

Will it be easy enough to use another PHY such as the Micrel KSZ8873RLL or the LAN9313 managed switch with BSD on the MZ? I can see huge advantages to using these for comms monitoring amongst other things. I know Wiz doesn't want this feature but having the ability to have a variant board with this would be great...

Cheers,

Dan


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PostPosted: Fri May 22, 2015 7:57 am 
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If you want to have hot insert capability for the sdcard - we had a long chat at arduino forum (Storage) where an arduinist asked how much current an sdcard takes when hot inserted (he asked as after insertion his system crashed).
The answer is an sdcard takes many (dozens) Ampers of current (for a small fraction of a usecs).
That is caused by multilayer ceramics capacitors (several uF large, low ESR) which are placed inside the sdcard's package. So an inrush current is much higher than the current limit of the LDO voltage regulator feeding the sdcard and its output voltage drops say by 2.5V.
At the end of the day my recommendation has been to use a separate LDO volt. reg. for the sdcard only, with rather low current limit (ie. 250-300mA) which will work as a current limiter, so the top LDO will not drop its voltage such it resets everything around.. Also a good filtering is required.
I recommend to experiment before finalizing :)
P.

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PostPosted: Fri May 22, 2015 9:30 am 
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The SDZL has two regulators - one for the core and one for the SD card / other peripherals.

The problem is the one for the core is too puny at the moment.

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