DS18B20 communication

General Discussion
21

Your older image, was missing the device-tree modifications needed to use 1-wire.

Today to do those modifications we use “u-boot overlays”, where u-boot will apply the overlay before the kernel loads. Your version of u-boot was to old to properly support the syntax and functionally required.

While you set the values in /boot/uEnv.txt, your version of u-boot did not know what todo with that information.

Regards,

22

Hi, i’ve tried to change ds18b20 pin connection and encounter an issue.
kernel:
5.10.168-ti-r72

My steps:

  1. Create custom .dts;
    BB-W1-00A0.dts (863 Bytes)

  2. Compile .dts and transfer .dtbo from host to BBB;

dtc -O dtb -o DS18B20-P8.46.dtbo -b 0 -@ BB-W1-00A0.dts
  1. Move .dtbo to /lib/firmware;
  2. Edit /boot/uEnv.txt
    enable line:
uboot_overlay_addr4=DS18B20-P8.46.dtbo
  1. Reboot.
    After BBB reboot i can see message:
    bone-w1
    bone-w11410×127 31.4 KB

According to it: the pin has been already occupied by some other peripheral (i assume by HDMI controller tda19988).
So, my questions are:

  1. How to disable tda19988 properly or how to use pin P8.46 properly?
  2. Why the message refers to PIN 41 if i’m trying to use P8.46?
    Thanks.
23

Mising: src/arm/overlays/BB-W1-P9.12-00A0.dts · v5.10.x-ti-unified · BeagleBoard.org / BeagleBoard-DeviceTrees · GitLab

&ocp {
	P8_46_pinmux { status = "disabled"; };
};

Regards,

24

added the line:
BB-W1-00A0.dts (929 Bytes)
on compile get the error:
Error: BB-W1-00A0.dts:21.5-9 syntax error
FATAL ERROR: Unable to parse input tree

25

i activate the following lines in the /boot/uEnv.txt:
disable_uboot_overlay_video=1
disable_uboot_overlay_audio=1
and deactivate
#enable_uboot_cape_universal=1
and now ds18b20 accessible on pin P8.46.

26

that’s another way to un-lock P8_46…

Regards,

27

why dtc returns an error message after adding lines:

&ocp {
	P8_46_pinmux { status = "disabled"; };
};
28

Your version of dtc is probally old and doesn’t support the newer syntax…

Regards,

29

it is Version: DTC 1.6.1
Is it old?
After update: device-tree-compiler is already the newest version (1.6.1-1).