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Thread: Propeller Mini EEPROM

  1. #1

    Default Propeller Mini EEPROM

    I'm eager to use the Propeller Mini -- it would be ideal in a new project of mine. Just enough I/O pins.

    But it's disappointing that the EEPROM is only 32k. I need non-volatile space above address $8000 to store data that will survive a program re-load.

    Any simple way around this? Is there a good reason why a 64k chip isn't standard? Looks like the same package and pinout as a 32k chip, so it could fit on the existing layout - or am I missing something?

    Thanks,

    Larry

  2. #2

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Larry C.
    Any simple way around this?
    Sure. Use a 64K EEPROM. Although the loader will recognize only the lower 32K, you'll have another 32K for storing non-volatile data via one of the I2C objects in the OBEX.

    -Phil

  3. #3

    Default Re: Propeller Mini EEPROM

    Connect another eeprom via the I2C pins that are connected to the first eeprom?

  4. #4

    Default Re: Propeller Mini EEPROM

    Thanks for the suggestions, but I don't think they really address the problem.

    The Propeller Mini is a fairly new Parallax product, so it may not be familiar. It puts a Propeller chip, two voltage regulators, xtal, and 32kB EEPROM on a 1.5 x .75 inch circuit board. Ideal for my project. Problem is that only I/O pins P0 through P18 are brought out. The others, including the clock and data pins for the EEPROM are not accessible. And I need all of the 19 available I/O lines, so -- no way to tack on an external EEPROM. And I DO need non-volatile storage above $8000.

    So, am I out of luck, or what? Any other suggestions?

    Larry

  5. #5

    Default Re: Propeller Mini EEPROM

    Laryy,

    Are you comfortable soldering SMT devices? If so, Parallax has the 64K in stock at two bucks:

    http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/EEPROM/List/0/SortField/4/ProductID/579/Default.aspx

    I
    f you not comfortable with the soldering job, I can do it for free. Send me the parts, and I can do a one day turnaround.

    Jim

    EDIT Looks like the Mini's are out of stock. Do you already have on?
    Infernal Machine

  6. #6

    Default Re: Propeller Mini EEPROM

    You could also use and I/O expander to gain 16-28 I/O's . What are you interfacing the I/O pins with?

    EDIT: Here's a thread about one I/O expander:

    http://forums.parallax.com/showthread.php/107967-mcp23017-(i2c)-example-code?highlight=Expander
    Last edited by Publison; 08-10-2013 at 06:14 PM. Reason: Added Thread
    Infernal Machine

  7. #7

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Publison View Post
    You could also use and I/O expander to gain 16-28 I/O's . What are you interfacing the I/O pins with?

    EDIT: Here's a thread about one I/O expander:

    http://forums.parallax.com/showthread.php/107967-mcp23017-(i2c)-example-code?highlight=Expander
    That sounds like it would work but doesn't it sort of defeat the purpose of using a small module like the Propeller Mini? I wonder why Parallax used a 32k EEPROM on the Mini? Is there a big difference in price between 32K and 64K?

  8. #8

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by David Betz View Post
    That sounds like it would work but doesn't it sort of defeat the purpose of using a small module like the Propeller Mini? I wonder why Parallax used a 32k EEPROM on the Mini? Is there a big difference in price between 32K and 64K?
    I can't see more than 50 cents difference, depending on the sourcing. I think all Propeller products should be shipped with 64K IMO.
    Infernal Machine

  9. #9

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Publison
    I think all Propeller products should be shipped with 64K IMO.
    I agree wholeheartedly.

    BTW, when the S2 hardware was being developed, two 32K EEPROMS were found to be less expensive than one 64K device. That was awhile ago now, so 64K pricing may have come down in the meantime.

    -Phil

  10. #10

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Publison View Post
    I can't see more than 50 cents difference, depending on the sourcing. I think all Propeller products should be shipped with 64K IMO.
    I think all of them do except this new Propeller Mini module. My guess is the BOM is very tight on it and the extra $0.50 might have been enough to force a retail price increase.

  11. #11

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Phil Pilgrim (PhiPi) View Post
    I agree wholeheartedly.

    BTW, when the S2 hardware was being developed, two 32K EEPROMS were found to be less expensive than one 64K device. That was awhile ago now, so 64K pricing may have come down in the meantime.

    -Phil
    Interesting Phil.

    The 64K device that Parallax sells, (ATMEL ?), is now obsolete at Mouser, ( I have not looked for other variations). Digikey does not show a 64KX8 at 3.3v . Must do more research.
    Infernal Machine

  12. #12

    Default Re: Propeller Mini EEPROM

    Something has always bugged me about two 32k EEPROMS. If they're both on the same I2C bus how does one get the low address range and the other get the higher one? Or are you required to put them on separate buses since I imagine that they think they have the same ID?

  13. #13

    Default Re: Propeller Mini EEPROM

    32K EEPROMS (and others) include up to three pins (A0 - A2) that must be strapped to select an address range. By strapping two chips differently, they can coexist on the same bus at different addresses.

    -Phil

  14. #14

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Publison View Post
    You could also use and I/O expander to gain 16-28 I/O's . What are you interfacing the I/O pins with?

    EDIT: Here's a thread about one I/O expander:

    http://forums.parallax.com/showthread.php/107967-mcp23017-(i2c)-example-code?highlight=Expander
    Publison:

    Yes, an I/O expander is probably the only way to go. But that means two additional chips -- expander plus EEPROM. This makes the whole project less attractive, since I plan to write it up and see about publishing, for radio amateurs and other hobbyists to duplicate. Oh, well...

    Also, thanks for your kind offer to modify a board. But, for the above reason, this probably wouldn't work.

  15. #15

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Larry C.
    But, for the above reason, this probably wouldn't work.
    I'm not sure I follow. Which reason is that?

    There are two ways to go about it:

    1. Replace the 32K chip with a 64K unit.
    2. Piggyback another 32K chip, strapping one of the address lines differently.

    -Phil

  16. #16

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Larry C. View Post
    Publison:

    Yes, an I/O expander is probably the only way to go. But that means two additional chips -- expander plus EEPROM. This makes the whole project less attractive, since I plan to write it up and see about publishing, for radio amateurs and other hobbyists to duplicate. Oh, well...

    Also, thanks for your kind offer to modify a board. But, for the above reason, this probably wouldn't work.
    I see where the extra chips may not work out for anything more that a one off. Since Parallax is in the process of producing more units, maybe we can convince them to put 64K devices on them, or make a new part number and charge one to two dollars extra?
    Infernal Machine

  17. #17

    Default Re: Propeller Mini EEPROM

    Thanks Phil, I'll have to study the Propeller Platform schematic carefully to see how the two EEPROMS are connected.

  18. #18

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Publison View Post
    I see where the extra chips may not work out for anything more that a one off. Since Parallax is in the process of producing more units, maybe we can convince them to put 64K devices on them, or make a new part number and charge one to two dollars extra?
    You bet!! I'd be willing to pay an extra buck or so for the added EEPROM.

  19. #19

    Default Re: Propeller Mini EEPROM

    Quote Originally Posted by Larry C. View Post
    You bet!! I'd be willing to pay an extra buck or so for the added EEPROM.
    The seed is planted.

    http://forums.parallax.com/showthread.php/149591-Please-put-a-64K-EEPROM-on-the-Propeller-MINI!?p=1200451#post1200451


    Infernal Machine

  20. #20

    Default Re: Propeller Mini EEPROM

    Package choices from one vendor are nicely shown here
    http://www.microchip.com/pagehandler...ackageMap.html

    Cheapest seems to be OnSemi, and the reel-level price comparison is
    CAT24C512 3,000: $0.419
    CAT24C256 3,000: $0.234

    Which is a price premium of 0.185 for the 64KB device.

    and I also think such products should include 5.0V in the regulator range. (but that is another topic)
    There should be more LDOs with outputs at 4.8V, and spec'd to include USB-chargers, as well as 'any plug pack'

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