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/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.

Debian                                            May 14, 2014                                        GPIOIIC(4)