I’m fiddling around with the I2C buses on my CV1800B audio board and noticed that when I do an ‘i2cdetect -r 0’ command to probe bus 0 there’s something generating an ACK at address 0x56. I don’t have anything connected to the bus on my board so it must be internal to the CV1800B SoC - does anyone know what this is? I skimmed through the datasheet and didn’t find anything that specifically mentioned this.
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My Duo board shows the same result, and I don’t think there’s anything on the board to respond on this line, except for the SoC itself.
It’d be curious to find out what it is.
Funcy，it not appeared in Duo S which boot from Arm。
Searching for ‘i2c’ in the device-tree, I saw that the state of i2c0 is ‘disabled’ (build/boards/cv181x/sg2000_milkv_duos_glibc_arm64_sd/dts_arm64/sg2000_milkv_duos_glibc_arm64_sd.dts)， so I didn’t see the ‘/dev/i2c0’ in the device。
i2cdetect command with options ‘-r’ means MODE_READ, you can try to run ‘ls -al /sys/bus/i2c/devices/’ and list all i2c devcie。
On Duo 256M, I²C #0 is also not available, I tested it on both boards (in RISC-V mode on SG2002).