Thanks all.I wish Microchip would have used a couple of extra pins on the device and allowed address setting the old fashioned way.
1. seems VCC & GND are valid voltages so 7 equal resistors say 1K @ 3.3V should be possible.
2. trimpot just seems so sloppy, else it would be a obvious choice and cheap too.
Nine equal resistors would work. Each tap would be a different voltage. Note that 0V and Vcc are not among the 8 voltages you can choose from. That's why you use 9 resistors.
No, 7 resistors and 0V and Vcc _are_ among the valid 8 voltages. Fig 1-3 in datasheet.
Any ideas on how to get all 8 addresses?
Quote from: MarkT on Oct 08, 2012, 03:04 amNo, 7 resistors and 0V and Vcc _are_ among the valid 8 voltages. Fig 1-3 in datasheet. Yes they are, but the allowed range for the first/last rows in the table is bigger.Think though: With 7 resistors the first voltage in your chain would be 1/7 VDD.At VDD=5.5 that's 0.7857V - nowhere near any of the target voltages in figure 1.3 (column V2).
Ah yes, that's odd, I'd have thought they would choose the on-chip resistors appropriate to allow equal external resistors (chip designers usually think carefully about the parts count on external circuit). So you need the two end resistors to be 3/2 the size of the other 5. Or use 9, make the end ones 1/2 the value of the others, and ignore the first and last taps.Still with 1% resistors 7 equal value ones would actually work I think, on-chip resistors have very good matching.
Well then they weren't thinking about external parts count... Odd.