GPIOIIC(4)             FreeBSD Kernel Interfaces Manual             GPIOIIC(4)

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 iicbb
           device iicbus

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

           gpioiic_load="YES"

DESCRIPTION
     The gpioiic driver provides an IIC bit-banging interface using two GPIO
     pins for the SCL and SDA lines on the bus.

     gpioiic simulates an open collector kind of output when managing the pins
     on the bus, even on systems which don't directly support configuring gpio
     pins in that mode.  The pins are never driven to the logical value of
     '1'.  They are driven to '0' or switched to input mode (Hi-Z/tri-state),
     and an external pullup resistor pulls the line to the 1 state unless some
     other device on the bus is driving it to 0.

HINTS CONFIGURATION
     On a device.hints(5) based system, such as MIPS, these values are
     configurable for gpioiic:

     hint.gpioiic.%d.at         The gpiobus you are attaching to.  Normally
                                just gpiobus0 on systems with a single bank of
                                gpio pins.

     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).  Because gpioiic must be a
                                child of the gpiobus, both gpio pins must be
                                part of that bus.

     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.

FDT CONFIGURATION
     On an FDT(4) based system, such as ARM, the DTS node for gpioiic conforms
     to the standard bindings document i2c/i2c-gpio.yaml.  The device node
     typically appears at the root of the device tree.  The following is an
     example of a gpioiic node with one slave device on the IIC bus:

     / {
             gpioiic0 {
                     compatible = "i2c-gpio";
                     pinctrl-names = "default";
                     pinctrl-0 = <&pinctrl_gpioiic0>;
                     scl-gpios = <&gpio1  5 GPIO_ACTIVE_HIGH>;
                     sda-gpios = <&gpio7 11 GPIO_ACTIVE_HIGH>;
                     status = "okay";

                     /* One slave device on the i2c bus. */
                     rtc@51 {
                             compatible="nxp,pcf2127";
                             reg = <0x51>;
                             status = "okay";
                     };
             };
     };

     Where:

     compatible      Should be set to "i2c-gpio".  The deprecated string
                     "gpioiic" is also accepted for backwards compatibility.

     scl-gpios sda-gpios
                     These properties indicate which GPIO pins should be used
                     for clock and data on the GPIO IIC bit-banging bus.
                     There is no requirement that the two pins belong to the
                     same gpio controller.

     pinctrl-names pinctrl-0
                     These properties may be required to configure the chosen
                     pins as gpio pins, unless the pins default to that state
                     on your system.

SEE ALSO
     fdt(4), gpio(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.

FreeBSD 13.1-RELEASE-p6        December 1, 2019        FreeBSD 13.1-RELEASE-p6