Ideas for a "ID" IC for Daughterboards

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

Not sure what's available to solve this problem, but I'm going to stock any number of different boards, each with a different function. The main board will need to poll (preferably on I2C bus) each board to see if its type is present in the "stack."

What I'd like is a specialized IC that I can produce multiple copies of an ID number in memory to use. I thought an I2C eeprom would work, but more than wouldn't work on the same bus with the same address. Then I thought I'd use a 10Fxxx part and make it into a quasi I2C eeprom with a unique address.

Is there already what I'm looking for available off the shelf?

If I do use a 10Fxxx part, any idea how much program space it would take to make it a I2C slave?

Thanks,

John

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

See the Dallas (Maxim) Silicon Serial Number ic's.

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

An I2C master is easy to write in software, but the I2C slave in software is a lot harder and not recommended.
There are no PIC10 processors with I2C hardware module, the cheapest PIC16 with I2C starts at $0.97.

jbmiller · Joined: 07 Oct 2006 Posts: 73 Location: Greensville,Ontario

Don't know if I'm reading your request right...been a loooong day but ..
If these daughter boards are your design, with a PIC, just store the 'type' in eeprom. Just one byte would give you 256 different 'types'. Another byte or two could be used for the serial number of that board. A couple more bytes could be used for firmware version info. This is similar to the way PC peripheral cards are coded.

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

John P · Joined: 17 Sep 2003 Posts: 331

Could you somehow give each board its own serial EEPROM chip (you can get them for less than $.25 each) and have the processor read it as I2C master? It's not clear to me how you intend to communicate with these processors, though. They can't do much.

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

Why do you want to use I2C for communication?
As you already found out addressing is a problem. Each unit requires a unique address and with a maximum of 256 addresses (1024 in special cases) you'll soon run into problems when you have no control about which units will be combined by the user.

An option I just found are the new Microchip UNI/O Serial EEPROMs:
- 1 wire bus
- 1-16kbit devices
- Prices starting at $0.23
These devices did look nice at first sight but it looks like the addressable devices are not out yet. Even when addressable parts come out the address range is limited to 8 bits, too small.

The Dallas (Maxim) Silicon Serial Number ic's are nice but have the problem you can only assign the number (-ranges) when you order large quantities.
A programmable version would be nice. This is provided in the DS2431, a 1kbit EEPROM. These cost $0.59 @ 1k
Because each chip has it's own unique 64-bit ID you can add as many devices to the same bus as you want without address conflicts. Program your product-type into the EEPROM and of you go.

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

Well, instead of using the 5-6 pin package parts, if I use an 8 pin part I get the addressing I need. The option of 8 different addresses should be enough.

Thanks for all the ideas.