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Why did you use the SAMD21 Mini to demo this product, instead of a “normal” Arduino? What changes, if any, would be needed to run the demo code in a Sparkfun Arduino Pro Mini, 5v, 16MHz? If the delays were taken out of the code, would the repeats of “loop()” vary significantly between the code on a SAMD21 and the Pro Mini specified?
1) Because the SAMD21 is a really cool and fast board and I think everybody ought to use it!
2) I don’t think any changes would be necessary, with the exception of setting the IDE up for a Pro Mini.
3) Yep, I’d expect it to run lots faster than a Pro Mini.
Shouldn’t the high side of the translator be connected to the 5v supply for the LEDs? This would put the logic and VCC at the same voltage, where using the controlling board’s 5v is likely to be off by ±100mv when compared to the 5v supply for the LEDs. Put another way, how much does it matter that the clock and data lines are 100mv different from the VCC?
In theory, you are correct. In practice, it’s a wash. Where the logic is concerned, you need to achieve a minimum threshold of 0.7*Vdd, or around 3.5V, and up to Vdd +0.3V for it to read as a high. So pretty big window. A couple of hundred mV difference shouldn’t be an issue.
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