NanoPi Duo2 I2C Problem

[ab0tj]

Hi all,

 

I am trying to use a MCP3426 I2C ADC chip with my NanoPi Duo2. I have compiled a custom kernel with the mcp3426 driver in it, but I can't get it to load. The problem seems to be that the chip uses address 0x68 which is the same address that the commonly used DS1307 RTC chip uses. I have blacklisted the ds1307 module which has stopped that module from loading, but somehow '/sys/bus/i2c/devices/0-0068/name' still claims to be a ds1307.  'echo mcp3426 0x68 > /sys/class/i2c-dev/i2c-0/device/new_device' results in a "Invalid argument error" with 'i2c i2c-0: Failed to register i2c client mcp3426 at 0x68 (-16)' being logged in dmesg, and apparently the -16 error means that address is already in use. 'echo 0x68 > /sys/bus/i2c/devices/i2c-0/delete_device' results in 'i2c i2c-0: delete_device: Can't find device in list'.

 

I should add that I can read the ADC using i2cget, but I would like to use the Linux iio interface.

Any ideas on where to go from here?

 

Thanks,
Alex

Edited July 5, 2019 by ab0tj
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[Igor]

Have you enable I2C in armbian-config? What do you get by scanning I2C busses?

[ab0tj]

Just now, Igor said:

Have you enable I2C in armbian-config? What do you get by scanning I2C busses?

 

Yes, I2C works otherwise.

# i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

 

[ab0tj]

In case anyone else comes across this, I answered my own question... I solved this by making a custom overlay:

/dts-v1/;
/plugin/;

/ {
        fragment@0 {
                target = <&i2c0>;
                __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <0>;
                        adc@68 {
                                compatible = "microchip,mcp3426";
                                reg = <0x68>;
                                status = "okay";
                        };
                };
        };
};

I still see "i2c i2c-0: Failed to register i2c client ds1307 at 0x68 (-16)" in dmesg, so something still seems to be trying to instantiate a ds1307. Maybe that's part of the base image? But at least my overlay claims that address before ds1307 can get to it.

[martinayotte]

1 hour ago, ab0tj said:

I still see "i2c i2c-0: Failed to register i2c client ds1307 at 0x68 (-16)" in dmesg, so something still seems to be trying to instantiate a ds1307. Maybe that's part of the base image?

It seems it have been added during April for a specific NanoPi which has this RTC onboard, but by mistake, it has been added to all NanoPi !

We will probably fix that soon ...

[ab0tj]

5 minutes ago, martinayotte said:

It seems it have been added during April for a specific NanoPi which has this RTC onboard, but by mistake, it has been added to all NanoPi !

We will probably fix that soon ...

Thanks, that explains it!