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bigandy · Posted: Thu Feb 08, 2007 10:01 am Post subject:

Hi folks,

Sorry, I don't know of a supplier for the ATtiny45 chips, other than trying the big suppliers like RS or Farnell. I know that Digikey will deliver internationally, although the postage charges can be a little steep. I've had a word with our purchaser at work (we use ATmega48s, 88s, and 168s here but buy them with our application firmware already loaded) and he doesn't know anywhere that sells them in batches of less than about 1000.

I'll hang fire on the I2C - USB thing for now though and wait to here of the results of the testing that is taking place. Out of interest though, what is this clock stretching feature?

Cheers
Andy
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ginge · Posted: Thu Feb 08, 2007 10:28 am Post subject:

Hi Andy,

It's a real shame about the 45's. You can get them from Farnell, but they always seem to be out of stock. We are thinking of using the 168 for now.
I don't want to get into using Digikey again, as I got stung for internation delivery +VAT + import fees last time around, making the chips I purchased very expensive.

Clock stretching is a feature that allows the I2C slave device to hold the clock line low to send a ""wait, not ready yet"" signal. The master controller then waits for the slave to release the clock line. This stops the data going out of sync.

A quick google found this is good guide here:
http://www.robot-electronics.co.uk/htm/using_the_i2c_bus.htm

Barry
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bigandy · Posted: Thu Feb 08, 2007 11:25 am Post subject:

I suppose the good thing about the Mega168 is that it does have a fair amont of room for codespace which would allow for future expansion perhaps?

I don't suppose you have tried getting samples out of Atmel, or one of their UK agents have you? Might work if you are only after a couple to play with. It's a shame Atmel don't subscribe to the Microchip philosophy and hand out free samples like sweets!

Cheers
Andy
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ginge · Posted: Thu Feb 08, 2007 11:36 am Post subject:

I requested some samples from Atmel a few days ago. I have heard nothing since. I ordered them through my employer so they should have honoured my sample request. You never know with Atmel, though!

B
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