Author Topic: why EEPROM?  (Read 4345 times)

mspohr

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why EEPROM?
« on: June 15, 2013, 08:54:15 pm »
Pardon my ignorance but why is EEPROM being offered as an optional extra goal?
Doesn't the device already have an EEPOM?
If not, how does it store programs?
I thought all Arduinos had an EEPROM.


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semicolo

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Re: why EEPROM?
« Reply #1 on: June 16, 2013, 02:35:31 pm »
The original Arduino due processor doesn't have EEPROM (but cheaper Arduinos and the digispark do have some), it's probably the same chip used on the DigiX, so there's no EEPROM by default.

digistump

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Re: why EEPROM?
« Reply #2 on: June 17, 2013, 04:00:38 pm »
There is no EEPROM on the chip used in the DigiX or Due - there is flash which is where programs are stored (true of the original ARduinos as well - programs on flash, program data on EEPROM).


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Bluebie

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Re: why EEPROM?
« Reply #3 on: June 19, 2013, 05:24:13 pm »
If you are careful, you can usually reprogram the flash memory in your AVR devices to store data also. The thing to it is that you usually have to erase pages, and those pages tend to be like 32 or even 512 bytes long or something like that. So it isn't like eeprom where you can erase and set a single byte. Flash also wears out quicker as you use it. And of course you need to be careful your program doesn't erase part of itself if you use flash!

mspohr

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Re: why EEPROM?
« Reply #4 on: June 25, 2013, 04:21:51 pm »
Thanks for all the responses.
I think I understand now... The processor has "flash" program memory but no way to store data (without odd gymnastics). The EEPROM adds the ability to store data.
I note that the DigiX also has the ability to plug in a micro memory card which I assume could also be used for data.

mspohr

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Re: why EEPROM?
« Reply #5 on: June 25, 2013, 04:32:28 pm »
Just to clarify... I seem to have had some crossed wires... I thought the DigiX had a micro SD socket but this must have been something else... I do see the Kickstarter page shows it hooked up to an external SD card so that is possible.


digistump

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Re: why EEPROM?
« Reply #6 on: June 25, 2013, 06:52:49 pm »
A microSD slot will be included on-board if we hit 100k (possibly if we don't, but for sure if we do). Since we've hit 75k the EEPROM will be on the board.