RetroBSD

2.11BSD operating system for microcontrollers
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 Post subject: Missing board
PostPosted: Thu Apr 02, 2015 8:31 pm 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
Hello RetroBSDs,
I had seen the project long ago on the mips website, and tried retrobsd on an explorer16, but I found retrobsd a fun project but for "old things" lovers.
LiteBSD is a modern and interesting project, I haven't any experience in unix developpement, but there something that i wish learn.

I would start with litebsd, but there are no suited cards, the microchip pic32 multimedia board is too expensive, and explorer 16 is too limited.
I intend to develop an "open source" pic32mz board for litebsd and others projects,
I'm open to ideas and tips.

Fixed points:
Pic32mz 144pin
On board LDO and analog reference
Can
Ethernet
Psram on EBI
SDcard (on SQI or SPI)
all unused pin on 0.1" double header
Board size 5*10cm or 10*10cm, 4 layer "dirtypcb" or other Chinese, for low cost boards and stencil.

Ideas:
Second SDcard,
external RTC with dedicated battery,
usb host and/or device
fpga companion (actel proasic3 or altera cycloneIV)

CAD:
altium or eagle

;)
PDP


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 Post subject: Re: Missing board
PostPosted: Fri Apr 03, 2015 12:37 am 
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Joined: Wed Oct 10, 2012 11:01 pm
Posts: 1079
Location: Sunnyvale, CA
Hi pdp11,

Actually, there is one board which is freely available and well suited for LiteBSD: chipKIT WiFire. It does not have Ethernet port, though. It has Wi-Fi controller, which is good, but the driver is still in development, expected to be available in a couple of months.

Here is a wiki page on LiteBSD site: https://github.com/sergev/LiteBSD/wiki/chipKIT-WiFire-board

An open source board for LiteBSD is a warm welcome! The feature list looks interesting. Not sure about FPGA, as it could increase the price too much. I would add a console port via some cheap uart-to-usb converter, like cp2102. For SD card, it makes sense to add a MOSFET in power control circuit, to be able to turn it off and on. It will make possible to recover from data i/o errors.

Best wishes,
--Serge


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 Post subject: Re: Missing board
PostPosted: Fri Apr 03, 2015 6:09 am 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
digilent microcontroller boards are not well distribuited in Europe: nor lextronic nor Trenz nor Mirifica have this board.
I note the sdcard power switch.
A question: a simple Pmos (on the power supply) with a slow gate control may be not enough for power off the card.
If the CS is not asserted, or other data pin is high, the sd card can be supplied by protection diodes. in this situation the current source is the microcontroller GPIO.
I don't know how sd card protections are made.
In this case a small bus switch can do the job.

Pietro


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 Post subject: Re: Missing board
PostPosted: Fri Apr 03, 2015 6:44 am 
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Joined: Wed Oct 10, 2012 11:01 pm
Posts: 1079
Location: Sunnyvale, CA
In Europe, the Olimex PIC32-HMZ144 board is probably easier to get. I did not try it myself, though.

The power control circuit for SD card should look like this:
Image

The problem here is that when the SD card encounters severe data error, it goes power down. To enable it again, the processor must toggle the power off/on.


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 Post subject: Re: Missing board
PostPosted: Fri Apr 03, 2015 4:52 pm 
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Joined: Mon Nov 12, 2012 1:34 pm
Posts: 1091
Hi Serge, pdp11 and all,

Might want to add a resistor to pull-down the SD Vcc so it gets to 0v in a known time since there is some sort of cap on Vcc inside some SDs.

IIRC spec. says all leads to SD must be below 0.5v for some time I can't seem to recall.

A driver might try a software reset and if that fails do the full power-down reset and then maybe a long power-down reset.

Connecting input pull-ups to Vcc of the SD card can make power-down code somewhat easier.

Wiz


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 Post subject: Re: Missing board
PostPosted: Sat Apr 04, 2015 4:18 pm 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
Pull-up on sd-vcc are a good idea, but don't avoid to push at 0 all sd card input for a correct reset.
For the console I think an ft230xs. the usb2uart presence is an implicit specification in those days.
Yesterday I created the symbols of pic32mz and psram for eagle.

Thanks for all advices

Pietro


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 Post subject: Re: Missing board
PostPosted: Sun Apr 05, 2015 4:22 pm 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
Phy question:
the less expensive choice is a smsc/mcp lan8720A or 8740, but small qfn are difficult to hand solder. Both are supported in harmony.
the old national DP83848c is easy to solder, proved reliable but quite expensive. I think is supported in harmony, it was used on old microchip demoboard.
the micrel KSZ8081MLX is not expensive and is tqfp, but I have no experience (never used) and I don't known if it's easy to integrate.

Any advice or suggestion?


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 Post subject: Re: Missing board
PostPosted: Mon Apr 06, 2015 2:20 pm 
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Joined: Mon Nov 12, 2012 1:34 pm
Posts: 1091
Hi pdp11,

I keep thinking that the chip is fast enough to bit-bang 10baseT and 10base2 [am I the last user?] .

I haven't written the code yet, but that would make multiple slow ethernet ports easy to add. A 200mhz processor doing 10mhz in software seems like it might just work?

SMOP - Consultant's joke: Small Matter of Programming :).

Lots of fun :).

Wiz


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 Post subject: Re: Missing board
PostPosted: Mon Apr 06, 2015 5:54 pm 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
I wrote a small specs,
I share for any advice or idea.
Schematic actually follows specs.

Best wishes,
Pietro


Attachments:
spces v00.odt [19.81 KiB]
Downloaded 455 times
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 Post subject: Re: Missing board
PostPosted: Tue Apr 07, 2015 5:33 am 
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Joined: Wed Oct 10, 2012 11:01 pm
Posts: 1079
Location: Sunnyvale, CA
Hi Pietro,

Some comments on the spec.
SQI interface seems pretty useless for SD card. SPI is the only choice.
IP101G is a nice variant of RMII phy. It supports low power mode. Price is $0.56 for 20pcs on aliexpress.com.
DP83848c phy is not supported by the current driver, but easy to add.
KSZ8081MLX does not support RMII interface, so it would occupy more pins on pic32 chip.

--Serge


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 Post subject: Re: Missing board
PostPosted: Tue Apr 07, 2015 10:57 am 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
I read the IP101G datasheet, but is not well distributed.
RMII is not a big pin advantage: from silicon errata
Quote:
7. Module: Ethernet Controller
MII pins that are not used
by the Ethernet module
during RMII operation are not released, and
therefore, lower priority functions on these pins are
not available in this mode. However, higher priority
functions on these pins, such as EBI and analog
inputs (for ADC and Comparators), can still be
used.

My actual but not definitive preference is the lan8720a, hoping for a decent quality stencil.

Thanks for the SQI explication.

PS: I have ordered the olimex board, to do some tests.

Pietro


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 Post subject: Re: Missing board
PostPosted: Tue Apr 07, 2015 10:19 pm 

Joined: Thu Apr 02, 2015 6:28 pm
Posts: 7
wiz wrote:
Hi pdp11,

I keep thinking that the chip is fast enough to bit-bang 10baseT and 10base2 [am I the last user?] .

I haven't written the code yet, but that would make multiple slow ethernet ports easy to add. A 200mhz processor doing 10mhz in software seems like it might just work?

SMOP - Consultant's joke: Small Matter of Programming :).

Lots of fun :).

Wiz

10base2 in use ;)
Bit bang 10 megabit? interesting, but I'm pretty ignorant.

54 pad bga 0.75mm is absolutly not routable without high quality etching or tented via: the fanout is impossible only on top layer.
I'm limited on 48 pad bga, that isn't a problem.

A question? a fast page read nor flash (ex spansion 29gl) for BSD is useful? it's not too expensive


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