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 15.1-STABLE-HBSD       December 1, 2019                     GPIOIIC(4)