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.