Overlay confusion

General Discussion
1

With the help of you all, I have a successfully working BME280 (Temp/H/P) sensor as well as well working extermal clock (DS3231)
I have been researching on how to utilize the D18B20 temp sensor (which I use several of on several different RPi’s) and followed instructions https://elinux.org/EBC\_Exercise\_31\_Dallas\_1-Wire
BTW, I use a BBB, latest Debian XFCE image.
I followed (as well as everything else in the instructional post):
’
Now edit /boot/uEnv.txt and find the line:
#uboot_overlay_addr4=/lib/firmware/<file0>.dtbo
and change it to
uboot_overlay_addr4=/lib/firmware/BB-W1-P9.12-00A0.dtbo
’
I assume that the P9.12 means pin12 on P9

After reboot, the D18b20 worked great! Got a Temp reading several times tried over.
Problem, now my ext clock and BME280 did not work anymore.
So, I commented out the line ’ uboot_overlay_addr4=/lib/firmware/BB-W1-P9.12-00A0.dtbo ’
rebooted, and clock and BME280 worked again, but not the DS18B20

So, as I mentioned in a previous thread, I obviously do not know what I am doing when it comes to overlays for sure.
My question then, as it is now, is it because the overlay_addr4 is the same in both my i2c and this W1-P912
If yes, how do I determine which addr to use? Any addr which is commented out in uEnv.tx? Which in my case could be addr0, addr1, addr2, addr3, addr5
Or,
is it something else?

2

u-boot will scan for eeprom and use these 4 variables:

uboot_overlay_addr0=<file0>.dtbo
uboot_overlay_addr1=<file1>.dtbo
uboot_overlay_addr2=<file2>.dtbo
uboot_overlay_addr3=<file3>.dtbo

Another 4 are available for end users to just use as they feel like it:

uboot_overlay_addr4=<file4>.dtbo
uboot_overlay_addr5=<file5>.dtbo
uboot_overlay_addr6=<file6>.dtbo
uboot_overlay_addr7=<file7>.dtbo

Each is loaded in order from 0 → 7…

If you don’t have any capes with an eeprom, feel free to use any from 0 → 7…

Regards,

3

Great - TY for quick response.
Just to clarify my question: I should NOT use the same addr in the overlay assignments. in other words, using addr in both overlays cancels out the former in uEnv.txt, yes?

4

uEnv.txt is just a variable assignment that get’s loaded into memory by u-boot…

So the last variable definition gets used…

Regards,

5

sorry for being dense, but your answer then is ‘yes’, if addr4 is used twice it would cancel one out?

6

Correct last define would be set

7

TY Again!