NAME

     gpioiic — GPIO I2C bit-banging device driver

SYNOPSIS

     To compile this driver into the kernel, place the following lines in your kernel
     configuration file:

           device gpio
           device gpioiic
           device iic
           device iicbb
           device iicbus

DESCRIPTION

     The gpioiic driver provides an IIC bit-banging interface using two GPIO pins for the SCL and
     SDA on the gpiobus.  gpioiic implements an open collector kind of output, as recommended by
     the standard, when driving the pins on the gpiobus, i.e, they are never switched to the
     logical value of '1', or they are '0' or simply open (Hi-Z/tri-state).  So the pullup
     resistors are required so gpioiic can work.

     On a device.hints(5) based system, like MIPS, these values are configurable for the gpioiic:

     hint.gpioiic.%d.at     The gpiobus you are attaching to.  Normally just gpiobus0.

     hint.gpioiic.%d.pins   This is a bitmask of the pins on the gpiobus that are to be used for
                            SCLOCK and SDATA from the GPIO IIC bit-banging bus.  To configure pin
                            0 and 7, use the bitmask of 0b10000001 and convert it to a
                            hexadecimal value of 0x0081.  Please note that this mask should only
                            ever have two bits set (any other bits - i.e., pins - will be
                            ignored).

     hint.gpioiic.%d.scl    Indicates which bit in the hint.gpioiic.%d.pins should be used as the
                            SCLOCK source.  Optional, defaults to 0.

     hint.gpioiic.%d.sda    Indicates which bit in the hint.gpioiic.%d.pins should be used as the
                            SDATA source.  Optional, defaults to 1.

     On a FDT(4) based system, like ARM, the DTS part for a gpioiic device usually looks like:

     gpio: gpio {

             gpio-controller;
             ...

             gpioiic0 {
                     compatible = "gpioiic";
                     /*
                      * Attach to GPIO pins 21 and 22.  Set them
                      * initially as inputs.
                      */
                     gpios = <&gpio 21 1 0
                              &gpio 22 1 0>;
                     scl = <0>;              /* GPIO pin 21 - optional */
                     sda = <1>;              /* GPIO pin 22 - optional */

                     /* This is an example of a gpioiic child. */
                     gpioiic-child0 {
                             compatible = "lm75";
                             i2c-address = <0x4f>;
                     };
             };
     };

     Where:

     compatible  Should always be set to "gpioiic".

     gpios       The gpios property indicates which GPIO pins should be used for SCLOCK and SDATA
                 on the GPIO IIC bit-banging bus.  For more details about the gpios property,
                 please consult /usr/src/sys/boot/fdt/dts/bindings-gpio.txt.

     scl         The scl option indicates which bit in the gpios should be used as the SCLOCK
                 source.  Optional, defaults to 0.

     sda         The sda option indicates which bit in the gpios should be used as the SDATA
                 source.  Optional, defaults to 1.

SEE ALSO

     fdt(4), gpio(4), gpioled(4), iic(4), iicbb(4), iicbus(4)

HISTORY

     The gpioiic manual page first appeared in FreeBSD 10.1.

AUTHORS

     This manual page was written by Luiz Otavio O Souza.