Using 2 EEPROM's with propeller.

DavidM

HI,

I would like to use 2 EEPROM's with the propeller. ( this is for salable production)

EEPROM-1, As the normal EEPROM for spin code
EEPROM-2, As extra memory to store a unique SERIAL NO , parameters and some user data ( not much under 1-2k)

I understand these are both on the I2C bus, I also have a LCD display that is using the same I2C bus.

Q1) When I load spin code to the eeprom ( via spin) , does the propeller IGNORE the second eprom?
Q2) Do I just parallel wire these as normal? ( i.e SCL, SDA wired in parallel)


The reason I want to do this is to update firmware and not have to worry about the serial no and user settings/data.

Q3) Is this a valid approach?

I believe I can get small EEPROM's quite cheap.


regards

Dave M

Leon

You could also use one of those little Dallas 1-wire devices.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

DavidM

Hi Leon,

I was think of just using one of these 24LC04B from microchip for under a dollar! And I need to use the I2C bus.

I am not sure of the chip you are suggesting?

Dave M

Nick Mueller

Or just a bigger EEPROM?

Nick

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Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO

simonl

Hi David,

Although I've not done any of this personally; I believe the answer to all of your questions is yes!

Leon & Nick also have valid approaches; probably the simplest is to use a bigger EEPROM - that'd be the same as what's done on the ProtoBoard, which has 64K. I'm sure there are several objects that will enable use of bigger EEPROM (as well as multiple EEPROMs).

HTH.

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Cheers,

Simon

---

www.norfolkhelicopterclub.co.uk
You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
BTW: I type as I'm thinking, so please don't take any offense at my writing style

DavidM

Hi Nick,

yes I can use a bigger eeprom, But once I administer a serial number I don't want to loose it , and I need to change the firmware if needed, I would expect to have hundreds of EEPROM's to update, I would have to manage the uploading of the spin to the propeller and make sure it does not write over the serial /user data. I also dont know how large my program is going to be yet!

To me, it would be easier to use two eeproms.


Thanks

Dave M

simonl

David,

So long as your data / S/N, etc are above 32K it should remain - even after re-programming.

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Cheers,

Simon

---

www.norfolkhelicopterclub.co.uk
You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
BTW: I type as I'm thinking, so please don't take any offense at my writing style

DavidM

Hi Simoni,

You have a valid point! So I gather that 32K is the maximum that spin can use for a program?, I mean can I still address more than 32K with data?


Dave M

simonl

Yup, you can access the EEPROM above 32K - not sure if there's a limit to how far you can go, but 64K is definitely doable [noparse]:)[/noparse]

As I understand it; the IDE downloads the full 32K - whether your program uses it all or not (I'm sure someone'll correct me if I'm wrong!). So, as long as your non-volatile data is written above the first 32K it will remain.

<edit>
Just to clarify; your program will need to use one of the I2C objects to put the non-volatile data above 32K. I don't think there's any way to get it there otherwise...
</edit>

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Cheers,

Simon

---

www.norfolkhelicopterclub.co.uk
You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
BTW: I type as I'm thinking, so please don't take any offense at my writing style

DavidM

Thanks Simoni,

I think I will just use 1 EEPROM!


regards

Dave M

Ale

most I2C devices have extra pins to change the address. The propeller will read the device with a specific address (external A0..2 = 0), if you use the address 001b for te second EE, that will make it not active when the propeller reads the address 000b, as you would expect.

DavidM

HI Ale,

I was wondering how different I2c devices get their address, I gather its done with pins?


thanks

Dave M

Ale

If they are the same part number, they have a specific address and sometimes pins to select low weight address. Have a look at the 24lc256 datasheet:
pdf1.alldatasheet.com/datasheet-pdf/view/74858/MICROCHIP/24LC256.html

In the first page you se that pins 1,2 and 3 correspond to the addresses A0, A1 and A3. The base address for this device can be seen in page 6 of the same datasheet, and how it is formet (0xa0 + A3A2A1b).

I hope is clear (ask if not). Some I2C devices does not have extra pins for addresses so you have to have one bus per device.

Have fun

DavidM

Thanks Ale


Dave M

Nick Mueller

> Some I2C devices does not have extra pins for addresses so you have to have one bus per device.

A bit more complicated to make things easier.
Different devices have different base-addresses (cast in silicon). Sometimes, the address can be selected with a different part-number (especially if it doesn't have address-pins).
So having more than one device on I2C, it is best to watch out for conflicts in the addresses (and maybe set a different address with the pins and/or the part).


Nick

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Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO

Ale

Ja Nick, you are right I forgot about the variations in part numbers, I think Microchip's I/O expanders are of this kind, or where ADCs ?, fuzzy memory of mine now