Re: RFC: "Comet" board with AT91RM9200

From: Hubert Hoegl (hoegl_at_fh-augsburg.de)
Date: 02/23/04 

Date: 23 Feb 2004 17:42:17 +0100

Jack Klein <jackklein@spamcop.net> writes:

> On 22 Feb 2004 02:36:51 +0100, Hubert Hoegl <hoegl@pc.com> wrote in
> comp.arch.embedded:
>
> A few comments based on putting together a board using this chip, and
> some of the others.
>
> > Hello,
> >
> > we are designing a microcomputer named "Comet" based on the Atmel
> > AT91RM9200 controller. All design files and software will be licensed
> > under the GPL.
> >
> > Currently the schematics is all what we have. We probably packed too much
> > building blocks into the design. Before we cut down the design and start
> > building the PCB it would be nice to hear what you think which optional
> > building blocks should turn to essential. The ESS blocks are necessary for my
> > job, the OPT blocks are nice to have, but make my design more complicated.
> >
> > ESS AT91RM92000 with PQFP-208 package
> > ESS USB host and function interface
> > ESS 16/32-MByte Flash Memory, 16-bit
> > ESS 64-MByte SDRAM, 16-bit
>
> The chip supports 32-bit SDRAM. Given that the maximum SDRAM bus
> speed is only around up to about 60 MHz, using 16-bit SDRAM would make
> it a real bottle-neck in the system when it is used. Why not 32-bit
> SDRAM?

You are right, this would be a serious bottleneck. I will check the
Micron MT48LC8M32B2 (8M x 32).

>
> > ESS RTC DS1338
> > ESS Twin-CAN Controller 82C900 or Oki ML9620
>
> A word of advice, stay away from the 82C900. It is a very broken
> piece of crap. We dumped it after all the problems we had on our
> first spin prototype boards. I would strongly suggest you look at
> something else. Especially if you are planning to use them in SPI
> mode. Some of the things that are broken with this chip have no real
> work arounds.

You may be right. As an alternative to the 82C900 I consider to use
the new ML9620
(http://www.okisemi.com/jp/datadocs/doc-eng/ml9620.pdf).
It has only one CAN interface, but that is not a problem for me.
Who has any experiences with this device?

> > ESS CPLD for custom tasks XCR3128XL-12TQ144C (with prototyping area)
> > ESS Debug- and Modem-Port (2 x RS-232)
>
> If you are using the on chip serial ports, they are very lame, no
> FIFOs so the processor has to deal with one interrupt for every
> character sent and every character received. TI and others make some
> very nice single and dual UARTs with 16 to 64 byte transmit and
> receive FIFOs fairly cheap.

Good idea, I've never considered this. Currently I will use the UARTs
only for debugging and console i/o. Maybe in the future I will add
IrDA datacommunication and a LIN interface. For LIN I first have to
check whether the UART is capable to do the necessary timing. If it is
not capable to do that, an external UART would be indeed the right choice.

> > ESS Single supply voltage 12 to 24 Volt, on-board voltage generation
> > ESS CompactFlash Interface in True-IDE mode (for WLAN cards)
> > ESS Connectors on Comet: Power, CAN, USB host/device, JTAG, RS-232, Ethernet
> > OPT 512K SRAM (to be used instead of SDRAM, e.g. for eCos)
> > OPT Serial Atmel Dataflash device, 8 MByte
> > OPT Epson graphics controller S1D13706 for QVGA displays
> > OPT Interface for simple 20x4 character LCD display
> > OPT PS/2 keyboard and mouse connector UR6HCPS2-SP40
> > OPT Audio Codec and Power Amplifier WM9705
> > OPT LIN Subbus
> > OPT MM/SD/DataFlash-Card Interface
> > OPT SmartMedia Interface
> > OPT SmartCard Interface
> >
> > Another design decision which is not yet clear is the type of the expansion
> > connector. I would like to add two connectors to the bottom of the PCB to
> > insert Comet into some target system. The connector type ranges from VG64 (64
> > pins, 2.54 mm) to Hirose/Molex (120 pins, 0.8 mm). What do you think?
> >
> > Thank you,
> >
> > Hubert
>
> How much is the board going to sell for?

I don't know what the board will cost. We currently have no plans to
sell the board. I hope that it will be cheaper than the commercial
boards: The Cogent CSB337 costs about 400 USD and the Atmel
AT91RM9200-DK ist even more expensive. I don't know the price for the
third board, the ARM9-LOM
http://www.dailzh.net/MyHtml/lom_arm9_project.htm. The costs will
mainly be determined by the PCB and by manufacturing (soldering)
costs. My funding includes schematics, PCB design, some prototypes (8
pieces) and testing. I hope that we finally arrive at working
prototypes somewhere in 2005. "We" is a freelancer and me, both working
parttime on the project. Due to the GPL license I hope that other
people out there find this project interesting. I could image that
somebody wants a Comet prototype to help testing or some manufacturing
company wants to build a pile of boards (probably I am far too
optimistic).

Hubert Hoegl
E-mail: Hubert.Hoegl@fh-augsburg.de
Home: http://www.fh-augsburg.de/~hhoegl/

> --
> Jack Klein
> Home: http://JK-Technology.Com
> FAQs for
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