Very possible I didn’t say what size I chose. I’ve gotten into a bad habit of simply putting down 0805 footprints and dealing with sourcing (part numbers) after the fact.
Usually with caps, it’s only a problem if you go much too small (in the event your device drawing a lot of current) or if you mistakenly replace it with a resistor (GULP)
I actually left them out! That’s something I do later in the assembly, as I promote having a box of various values around and standardizing on 0805s for your assembly. These are the kits I use:
Aha! The R5 and R7 are discussed in the LDR Analog Input video!
Still not sure what R1-R4 should be.
I’ve looked through the DS7505 data sheet, and while it calls for a pull up resistor on the O.S. line, it doesn’t specify one. But it’s just an open source “switch”, so it should work like a plain pull up resistor, as one would with a pushbutton? If so, 10k ought to work. That’d give a current flow of 330uA, which should be safe for the DS7505 - it seems to show max OS current as 4mA, so this would put it a full order of magnitude below that.
But nothing on R2-R4. Are these just protection resistors? The datasheet gives a safe voltage range (-3V to +5.5V), for pins A0-A3, but in Note 6 simply assumes they are either Gnd or VDD.
10K is fine for R1.
R2-R4 can be 0 Ohm or any small value such as 1K or less.
R5, R7 are not critical, depending on what you are trying to achieve with your measurement. As the LDR has a range of ~25K to 500K you could start with a value of about 22K for both. Alternatively you could use a small value (or even 0 Ohm) for R7 and a large value such as 100K for R5. Any necessary calibration can be done if software.
Testing the photo resistor I got shows a range of 18k when brightly lit (shining phone “flashlight” directly at sensor) down to 300Ohm when completely covered.A 10k resistor in R5 (and 0 in R7) should work - even if the resistance spikes to 20k due to even brighter light, PR_TOP should not exceed 3.3V.
The i2c video does state 0R for R2-R4.
Just wish all this was in one place - I want to finish building the board before starting to program it.
I was going by the LDR listed on the schematic that has a resistance that decreases when illuminated. 10K for R5 sounds okay in your case, this will give a voltage that increases when illuminated when measured at PR_TOP. To get a voltage that decreased with illumination you would swap the values for R5 and R7 and measure at PR_BOT.
I don’t have the schematic for the adapter board but if that is the case then the 5V label is rather misleading. If the jumper selects between 5V and 3V3 for the PWR_IO pin then yes, changing the jumper would the correct solution, and use a value of Ohm for R5.
Edit: Found the schematic for the Teensy adapter and that makes a little more sense. The 5V label on the sensor board should probably be renamed. changing that jumper would indeed be the way to go.