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GPIOIIC(4)		     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 config-
     urable 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  hexa-
			    decimal 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, de-
			    faults to 0.

     hint.gpioiic.%d.sda    Indicates  which  bit  in  the  hint.gpioiic.%d.pins
			    should  be	used as the SDATA source.  Optional, de-
			    faults 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 typi-
     cally  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 con-
		 troller.

     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			December 1, 2019		      GPIOIIC(4)
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