Hello Community!

 

I am struggling with assigning numbers to I2C buses in my BPi, doing the same(?) thing in two different ways i am getting two different results.

 

By default, there is only /dev/i2c-0 node available, AFAIK because HDMI uses this bus. 

 

1.  Using build-in overlay for i2c0 bus (overlays=i2c0 in /boot/armbianEnv.txt) enables another i2c bus. In this case, /dev/i2c-0 is the bus connected to pins 3 and 5 at 40-pin header. The other bus (enabled by default) becomes /dev/i2c-1. It doesn't matter how many times i reset my board, assignment doesn't change.

2. The second way is to create my own overlay by cloning this code and compiling it with armbian-add-ovelray command. It also enables another i2c bus. However, in this case the buses are swapped, /dev/i2c-0 doesn't change, the newly created bus is /dev/i2c-1 and works fine with sensors connected to pins 3 and 5. This enumeration also doesn't change after reboot.

 

Can someone tell me why does it happens? Does the cod for build-in overlay differ from the shared one?

Please, be patient for newbie user

 

Here is the version:
 

cat /etc/armbian-release 
# PLEASE DO NOT EDIT THIS FILE
BOARD=bananapim2zero
BOARD_NAME="Banana Pi M2 Zero"
BOARDFAMILY=sun8i
BUILD_REPOSITORY_URL=https://github.com/armbian/build
BUILD_REPOSITORY_COMMIT=7184c5aa8
LINUXFAMILY=sunxi
ARCH=arm
BOOT_SOC=
IMAGE_TYPE=stable
BOARD_TYPE=csc
INITRD_ARCH=arm
KERNEL_IMAGE_TYPE=zImage
KERNEL_TARGET=legacy,current,edge
KERNEL_TEST_TARGET=current
FORCE_BOOTSCRIPT_UPDATE=
FORCE_UBOOT_UPDATE=
OVERLAY_DIR="/boot/dtb/allwinner/overlay"
VENDOR="Armbian"
VENDORDOCS="https://docs.armbian.com"
VENDORURL="https://www.armbian.com/"
VENDORSUPPORT="https://forum.armbian.com"
VENDORBUGS="https://www.armbian.com/bugs"
BOOTSCRIPT_FORCE_UPDATE="no"
BOOTSCRIPT_DST="boot.cmd"
VERSION=25.2.2
REVISION=25.2.2
BRANCH=current

 

Hi,

 

to me it looks like there's no difference in the overlay you took from the sunnxi-DT-overlays repo and the one in the Armbian image you're running which comes from this patch:

 

https://github.com/armbian/build/blob/fad71e196230690a2c8205ec977dcc5a653f9746/patch/kernel/archive/sunxi-6.12/patches.armbian/arm-dts-overlay-Add-Overlays-for-sunxi.patch#L4136

 

Normally according to the doc, i2c-0 is the bus connected to pins 3 an 5 (PA11, PA12), isn't it ?

 

https://wiki.banana-pi.org/Banana_Pi_BPI-M2_ZERO

 

So the behaviour looks correct when you enable the built-in  i2c0 overlay.

I cannot say why the numbering changes when you use your own overlay. 

 

Eventually you could follow the below link and provide 1 log after you boot the build-in overlay and 1 log after you boot with the custom one.

 

 

Thank you for your reply.

Unfortunately, I don't have that much time to delve into it at the moment (I thought it would be easier to explain).

I will come back to this topic as soon as possible.