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Mapping linux driver to GPIO

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Hi All,

I have currently mapped two GPIO to be used with slave devices to operate with I2C. I also have checked the mapped GPIO by writing 1/0 through command like and checking the signal through an oscilloscope.

I would like to map the I2C driver already there in the kernel to be used with these two GPIO pins.

Question:

1. How do I map the linux kernel I2C driver to GPIO so that I can communicate with the slave devices.

2. There are 4 i2c commands: i2cdetect, i2cdump, i2cget, i2cset. Is there any documentation on how to use them?

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  • 0

    Hi yathindra,

    I guess I am a little confused about what you are trying to accomplish.  Are you only using the GPIO to show that you can toggle them successfully externally on the board?  If so, then I suggest removing the GPIO to those pins and instead using the Xilinx AXI I2C IP to connect the processor to the external I2C slave devices.

    You can find more information on how to implement the driver from the software side here:

    http://www.wiki.xilinx.com/Linux+I2C+Driver

    The driver mapping that needs to occur in order to reach the AXI I2C controller happens within the device tree.  Here is an example devicetree entry for an I2C block implemented within the Programmable Logic:

    axi_iic_0: i2c@41600000 {
                            #address-cells = <1>;
                            #size-cells = <0>;
                            compatible = "xlnx,xps-iic-2.00.a";
                            interrupt-parent = <&intc>;
                            interrupts = <0 29 4>;
                            reg = <0x41600000 0x10000>;
                    };

    We have had good results using i2cdetect and i2cdump by simply following the man page for these commands:

    http://linux.die.net/man/8/i2cdetect

    There is also the possibility of doing I2C over GPIO using this Linux driver but that practice is definitely not recommended for use in a real world application:

    https://lwn.net/Articles/230571/

    Regards,

    -Kevin

  • 0 in reply to zedhed

    Thanks for the reply. I am currently working on these lines. 

    To clarify, I am currently using GPIO connected to slave devices through I2C bus.

     

    I am kind of confused right now about the entire procedure. 

    Since there is an I2C driver already in the kernel, may I know why I need to use/modify http://www.wiki.xilinx.com/Linux+I2C+Driver  ?

    Wont a simple mapping of address space, probably by using mmap of the inbuilt I2C and address of GPIO be enough?  That also brings us to the question, how to actually do data transfer using i2cset and i2cget. From the linux man pages, I understood that they are just helper functions.

    Please share your thoughts on this.

    Thanks

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  • 0 in reply to zedhed

    Thanks for the reply. I am currently working on these lines. 

    To clarify, I am currently using GPIO connected to slave devices through I2C bus.

     

    I am kind of confused right now about the entire procedure. 

    Since there is an I2C driver already in the kernel, may I know why I need to use/modify http://www.wiki.xilinx.com/Linux+I2C+Driver  ?

    Wont a simple mapping of address space, probably by using mmap of the inbuilt I2C and address of GPIO be enough?  That also brings us to the question, how to actually do data transfer using i2cset and i2cget. From the linux man pages, I understood that they are just helper functions.

    Please share your thoughts on this.

    Thanks

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