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Topic: Stackable shields (Read 4 times) previous topic - next topic

aballen

ok, so I wasn't totally off on the I2C thing.  It sounds like a great idea, but it definitely introduces added costs(however large or small) and  requires some software for the 2313.

Simple jumper wires don't seem to create any additional work other than in the PCB design, and add maybe a nickel to cost for the jumper wires.... kinda seems similar to my idea about jumpers, just easier to implement.

I'm gonna play with some stacky headers this weekend too.... but they are also a bit pricey...

Any other ideas?

westfw

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for example it would only increase the price by about 3 dollars.
~$1.45 for a ATtiny2313 for the I2C interface and ~$0.75 for a DIP switch to select the address.

It would increase the COST by about $3... (oops.  The Lady already pointed this out!)
Isn't implementing an I2C "slave" difficult, though?  Or was that SPI?  There are a couple protocols where the master has it easy, but the slave has to be able to toggle a signal on a clock edge (or similar), which is tough to do in SW.

nkcelectronics

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I just found a great example of a very simple solution here, Totally user configurable... with just a few wires.
http://www.ladyada.net/make/eshield/wire.html

I think the simple solutions are often the most elegant, kudos to you, ladyada.




Hmmm... the protoshield with breadboard already had the same concept... maybe we get so advanced on an idea that we forget to get back to the basics...

nkcelectronics

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ok, so I wasn't totally off on the I2C thing.  It sounds like a great idea, but it definitely introduces added costs(however large or small) and  requires some software for the 2313.

Simple jumper wires don't seem to create any additional work other than in the PCB design, and add maybe a nickel to cost for the jumper wires.... kinda seems similar to my idea about jumpers, just easier to implement.

I'm gonna play with some stacky headers this weekend too.... but they are also a bit pricey...

Any other ideas?

aballen, if you want to have many-to-many combinations, it is just impractical with jumpers.  That is why buses were invented.  I2C is the way to go.  You can hide the complexity of i2c by writing an abstraction library that talks to a master I2C shield, which assigns device numbers to different shields and do the master coordination... every shield, when powered-up and connected to an i2c bus, tries to talk to the master shield... Arduino does the same... actually ladyada already put a price on this shield... $12... it is just a tiny AVR + PCB + software

nkcelectronics

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i wont copy and paste a 5-page long email thread i've had regarding orders placed with 'em, suffice to say, the prices are good because you're unlikely to ever get the parts.

Heh. I've always gotten my stuff. Sometimes it takes a little while if you order one of their boards (waiting on a 3.3v switching regulator board atm) but the components come fast.

Futurlec is reliable, but slow (2-3 weeks)... and the pricing is OK for small to mid size orders... it is not so cheap if you order large quantities.  

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