If resistor R23=0 (see below schematics), then log.1 cannot be set on pin Analog A7. Is it really true?
Depends which schematic you look at. The Giga documentation page indicates that 0R is not populated...
You are correct in saying that if R23 was 0Ω, then you would not be able to get a voltage on A7.
However R23 might not be fitted.
Look at this photograph taken from the Giga R1 WiFi product page, you can clearly see that R23 (arrowed) is not fitted:
Does it? * See edit below
This is what's on Arduino GIGA R1 WiFi — Arduino Official Store
https://docs.arduino.cc/resources/schematics/ABX00063-schematics.pdf
It has C55, C56, and C4 marked as DNP (Do Not Place/Populate) - but nothing to indicate that R23 is not fitted:
EDIT
Aha - that schematic came from the Guide to GIGA R1 Advanced ADC/DAC and Audio Features:
- The ArduinoTeam developers need to correct the circuit ABX00063 version 1.2 (02/23/2023) and cross out the resistor R23.
- Resistor R23=0 should not be installed on the board at all, so as not to damage the microcontroller through analog input A7. Instead of the resistor R23 on the PCB, it is better to put a suppressor.
Not cross it out - mark it as DNP.
As @JohnLincoln said in post #3, the tracking is there - it's just the component is not populated.
Addendum
There's been several posts about this sort of thing lately - it seems that Arduino are pretty poor at properly & consistently identifying DNP/"Not Fitted" parts:
Thanks for bringing this up, we are looking into this.