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Recommended Ethernet MAC/PHY?

Discussion in 'Embedded' started by Randall Nortman, Sep 8, 2005.

  1. Thanks to all who responded to the previous thread I started regarding
    AVR+Nut/OS vs. ARM+Linux. I have decided to go with an AVR (Mega128)
    with external SRAM (32kB or 64kB, probably) and an external ethernet
    MAC. (I would still consider the AT91SAM7X, except that it doesn't
    seem to be generally available yet. If anybody knows where I can get
    it, I'll give it a shot.) For the OS and, more importantly, TCP/IP
    stack, I'm still looking at Nut/OS, but have also expanded the options
    to include Contiki and FreeRTOS (with uIP), or possibly just uIP with
    no external OS.

    But, there remains the question of which Ethernet chip to use. I only
    need 10Mbps, but I wouldn't mind running in 100Mbps mode. (At 16
    MIPS, I'm not going to be able to saturate even 10M, but it would be
    nice to be able to put these things on a hub with 100Mbps nodes
    without slowing everything to 10Mbps. Some hubs can mix 10/100 right,
    but not all.) The RTL8019AS is apparently popular with hobbyists, but
    it seems difficult to source (not carried by Digi-Key, for example).
    Still, it seems like I can most easily find pre-written drivers for
    this chip, so I wouldn't need to write my own. (I've never written
    Ethernet code, so I'm a little clueless about how it all works.)

    Anybody have other recommendations? My primary concerns are, in
    priority order: (a) reliability, (b) getting the TCP/IP stack up and
    running with a minimum of coding in one or all of the above-mentioned
    OS environments, (c) minimizing the number of traces on the PCB, chip
    footprint, and heat generation, and (d) being able to buy the chip
    cheaply and reliably in small/moderate quantities (from half a dozen
    for prototyping to a couple hundred for subsequent production).

    Opinions on the three operating systems I mentioned (Nut/OS, Contiki,
    FreeRTOS+uIP) would also be appreciated. My primary concern here is
    that it be as close to working out of the box (or rather, out of the
    ..tar.gz file) as possible. It would also be nice to be able to
    migrate easily to an ARM7 chip in the next generation.

    And lastly, I don't suppose there are really a lot of differences, but
    I'm also going to need to choose an external SRAM chip and one of
    those shielded RJ45 jacks with integrated transformers. If there are
    any particular features I need to look for or gotchas in making these
    selections, I'd appreciate a tip. ;)

    TIA,
     
    Randall Nortman, Sep 8, 2005
    #1
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  2. Randall Nortman

    David Kelly Guest

    If staying with AVR was a done deal then my top choice for grafting
    ethernet to the AVR was the Microchip ENC28J60. First I heard it was to
    ship in July, then August. http://www.edtp.com/ currently lists
    September 15.

    ENC28J60 has a lot of advantages, all on paper because the part isn't
    shipping. Small pin count. Easy SPI interface. Reasonable price. And
    will one day be available from every source currently selling PICs.
     
    David Kelly, Sep 9, 2005
    #2
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  3. Randall Nortman

    Richard H. Guest

    As you point out, running 10/100 let's you auto-negotiate the speed,
    making your product more compatible. You'll encounter some environments
    that require 100Mbps connections, even if the device doesn't call for
    it. It also avoids problems with duplex mis-match, which causes
    unreliable connections. (Negotiating to full-duplex yields a
    higher-performance connection too, though not a concern for you.)

    Look at the ASIX AX88796l 10/100 ISA chip. It uses a modified NE2000
    driver (like the Realtek RTL8019AS). You can source proto boards from
    http://www.edtp.com (you'll find Mega128 drivers for the ASIX there too).

    You can buy in small quantities direct from the manufacturer ($175 for
    25x, +$30 S&H and ~$45 T&T fee [wire transfer fee charged by your
    bank]). http://www.asix.com.tw

    However, it's QFP-128 footprint (slightly wider than the Mega128), it
    should run in 8-bit mode (but I haven't tried it); and it requires 5
    address lines, 5 control lines, and 8/16 data lines. Pulls 95mA
    typical; runs cool to the touch. (Microchip's SPI controller is really
    the next step WRT fewer signal lines, but IIRC it also pulls 250mA at 10Mb.)

    For the jack, Bothhand NU1S041C-434 RJ-45 w/ magnetics & 3 LEDs is very
    popular. $3.50 each in tubes of 28 + $10 S&H from
    http://www.bothhandusa.com. (Some others are Delta, Pulse, Bel Fuse,
    HALO, MagJack, Tyco, Molex, etc.)

    HTH,
    Richard
     
    Richard H., Sep 9, 2005
    #3
  4. Randall Nortman

    Tilmann Reh Guest

    I would also think in that direction.

    Using "PC board mainstream" parts always have the risk that these
    probably become obsolete half a year after design-in. Chips that are
    targeted to industrial electronics normally have much longer lives.
     
    Tilmann Reh, Sep 9, 2005
    #4
  5. Randall Nortman

    pbreed Guest

    Why the Mega128???

    Let's look at silicon costs...

    Mega 128 $8.00
    SRAM $1.50
    Mac Phy $4.00
    Ethernet Jack $1.95

    Total Silicon 15.45


    Freescale/Coldfire 5270 7.95 (We currently use the 150Mhz version $9.54)
    512K Flash 1.25
    10/100 Enet Phy 1.50
    10/100 Etyhenet Jack 1.95
    Total Silicon 12.65

    I'd personally ad 2Mbytes of SDRAM to make things easier
    Total Silicon with SDRAM $14.15

    over $1.00 cheaper than the MEGA 128 solution.

    This gives you a far more capable unit.
    100Mhz 32 bit CPU, 512K flash ,2M bytes of SRAM, 3 uarts, CAN, I2C, SPI, 16 timers,
    10/100 Ethernet.

    If you need A/D from the Mega then substitute a freescale 5282 for the CPU and Flash.

    We offer turnkey ready to use modules based on this part
    You can start your software development today.

    We will sell you the design, hardware, software tcp, tools,. compiler linker debugger,
    with full source etc..etc... . so you can produce your own modules for $24,500
    This is a site license for an unlimited number of designs, with no royalties.
    This price includes a design review of your first hardware design based on our
    design.
    If you just wanted to produce a clone of our modules, the PCB designs are even included.

    If you have realistic costing for your engineering time you would
    be hard pressed to do a hardware design and port a tool set, RTOS and tcpip stack to
    any design for 24K.

    As a general comment, some people are scared by the word RTOS, it's there and it keeps all
    the TCP/IP services running in the background, but for your own programming you don't need to
    use it at all, just write your code in the way you are accustomed, a single threadof execution
    with interrupts providing any necessary scheduleing.

    See
    http://www.netburner.com/products/processors/Mod5270.htm

    and

    http://www.netburner.com/products/licensing.htm

    RTOS example:

    http://www.netburner.com/projects/RtosVsInfiniteLoop.pdf


    Paul
     
    pbreed, Sep 9, 2005
    #5
  6. Randall Nortman

    linnix Guest

    It doesn't make sense with AVR, if you need ethernet.
    AT91SAM7A,7S or 7X are just as good.

    AT91SAM7X seems to be your best choice. If you are concerned about 7X
    availabilty, goes with 7A or 7S first. If you are starting your
    project soon, perhaps you can get the 7X when you are ready for it.
    Switching from 7A or 7S to 7X is a lot easier than from AVR to ARM.
     
    linnix, Sep 9, 2005
    #6
  7. Because it's what I'm familiar with. Bad reason.
    Upon further investigation, I have come to agree.
    I am convinced. I've been looking into the availability of the
    AT91SAM7X, and Atmel claims the distributors will have them Oct 1.
    I've got calls into the distributors to see if that's for real. Only
    Digi-Key has responded so far, and the responses was something along
    the lines of "Huh? Ain't never heard of it." We'll see if anybody
    else comes through.

    I can probably wait until mid-October to get the part. But then I
    have another problem -- I need a cheap Ethernet PHY (no MAC, since the
    7X has on-chip MAC). And the problem is that the low-volume suppliers
    I usually use (Digi-Key and Mouser) have pretty poor selections of
    PHYs. (Digi-Key is charging ~$8+ for a simple 10/100 PHY... seems
    outrageous.) In fact, most of the parts I've been looking for during
    this project (which is a bit more complex than things I've undertaken
    before) are expensive or non-existant in Digi-Key's catalog, so
    perhaps it's time I branch out to other suppliers -- any suggestions
    (of suppliers and/or parts)?

    Thanks,
     
    Randall Nortman, Sep 9, 2005
    #7
  8. Randall Nortman

    pbreed Guest

    I can probably wait until mid-October to get the part. But then I
    How many are you trying to build?
    (Do you just need samples or 100.1000.10000?)


    We have had good luck with the Davicom DM9161
    Probably at least a 100pc minimum buy.

    Micrel has some new very low cost PHY chips as well...
    you could probably get dsitributor samples....
    (We are just starting to use some of these)

    Lastly try the DP83847ALQA56A-ND $5.70 Q1 from digikey.
    It is a fine PHY, but be aware that placing the LLP56 package on a PCB is a bitch.


    Paul
     
    pbreed, Sep 9, 2005
    #8
  9. Initial prototype run of 5 units, then a first production run of about
    50, and then (if all goes well), subsequent runs of 100-300. The
    larger runs are easy, but how do I get small quantities for
    prototyping?
    I've seen Davicom mentioned, so I've been looking for anybody who
    carries Davicom, with no luck... where can I get them in the US?
    Yeah, the prototypes will be hand-soldered by yours truly, so leadless
    packages are probably not such a good idea. How do the pros handle
    prototype assembly of things that can't be hand-soldered? I'm not a
    pro, just an amateur hack who got talked into doing this project. I
    guess that makes me a pro now, but I don't feel like one. In
    particular, trying to navigate the sea of manufacturers, parts, and
    distributors is getting a little overwhelming.
     
    Randall Nortman, Sep 9, 2005
    #9
  10. Randall Nortman

    linnix Guest

    We simply order the prototype board with the part mounted. Dm9161AE
    (TQFP 48) is not a problem for the prototype shop. For productions,
    they are $2 to $4 each, depends on qty.
     
    linnix, Sep 9, 2005
    #10
  11. Randall Nortman

    linnix Guest

    I just got a quote from the shop. They can provide the Dm9161AE
    (ethernet phy) and mount on the prototype board for $5 additional. The
    prototype boards are $5 to $10 each, depending on size. Mininum order
    of $50. See:

    http://pcb.info-for.us
     
    linnix, Sep 10, 2005
    #11
  12. Randall Nortman

    jpinkham Guest

    linnix, Randall,

    Were you able to find a US distributer for direct purchase/sample of th
    DM9161?

    Jason




    This message was sent using the comp.arch.embedded web interface o
    www.EmbeddedRelated.com
     
    jpinkham, Sep 13, 2005
    #12
  13. Randall Nortman

    linnix Guest

    We are getting some for $3 each. How many do you need.
     
    linnix, Sep 13, 2005
    #13
  14. SAM7X samples has been seen!
     
    A. P. Richelieu, Sep 14, 2005
    #14
  15. There are distributors with samples right now...
    If you download the evaluation kit manual ,then there are some schematics
    with a Davcom PHY.
    You probably want to use RMII to save pins.
    If you need industrial temp range, then the Davicom part will not cut it but
    a micrel part cn do
    RMII + industrial.
     
    A. P. Richelieu, Sep 14, 2005
    #15
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