1.\" Copyright (c) 2013, Luiz Otavio O Souza <loos@FreeBSD.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd December 1, 2019 28.Dt GPIOIIC 4 29.Os 30.Sh NAME 31.Nm gpioiic 32.Nd GPIO I2C bit-banging device driver 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following lines in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device gpio" 39.Cd "device gpioiic" 40.Cd "device iicbb" 41.Cd "device iicbus" 42.Ed 43.Pp 44Alternatively, to load the driver as a 45module at boot time, place the following line in 46.Xr loader.conf 5 : 47.Bd -literal -offset indent 48gpioiic_load="YES" 49.Ed 50.Sh DESCRIPTION 51The 52.Nm 53driver provides an IIC bit-banging interface using two GPIO pins for the 54SCL and SDA lines on the bus. 55.Pp 56.Nm 57simulates an open collector kind of output when managing the pins on the 58bus, even on systems which don't directly support configuring gpio pins 59in that mode. 60The pins are never driven to the logical value of '1'. 61They are driven to '0' or switched to input mode (Hi-Z/tri-state), and 62an external pullup resistor pulls the line to the 1 state unless some 63other device on the bus is driving it to 0. 64.Sh HINTS CONFIGURATION 65On a 66.Xr device.hints 5 67based system, such as MIPS, these values are configurable for 68.Nm : 69.Bl -tag -width ".Va hint.gpioiic.%d.atXXX" 70.It Va hint.gpioiic.%d.at 71The 72.Nm gpiobus 73you are attaching to. 74Normally just gpiobus0 on systems with a single bank of gpio pins. 75.It Va hint.gpioiic.%d.pins 76This is a bitmask of the pins on the 77.Nm gpiobus 78that are to be used for SCLOCK and SDATA from the GPIO IIC 79bit-banging bus. 80To configure pin 0 and 7, use the bitmask of 810b10000001 and convert it to a hexadecimal value of 0x0081. 82Please note that this mask should only ever have two bits set 83(any other bits - i.e., pins - will be ignored). 84Because 85.Nm 86must be a child of the gpiobus, both gpio pins must be part of that bus. 87.It Va hint.gpioiic.%d.scl 88Indicates which bit in the 89.Va hint.gpioiic.%d.pins 90should be used as the SCLOCK 91source. 92Optional, defaults to 0. 93.It Va hint.gpioiic.%d.sda 94Indicates which bit in the 95.Va hint.gpioiic.%d.pins 96should be used as the SDATA 97source. 98Optional, defaults to 1. 99.El 100.Sh FDT CONFIGURATION 101On an 102.Xr FDT 4 103based system, such as ARM, the DTS node for 104.Nm gpioiic 105conforms to the standard bindings document i2c/i2c-gpio.yaml. 106The device node typically appears at the root of the device tree. 107The following is an example of a 108.Nm 109node with one slave device 110on the IIC bus: 111.Bd -literal 112/ { 113 gpioiic0 { 114 compatible = "i2c-gpio"; 115 pinctrl-names = "default"; 116 pinctrl-0 = <&pinctrl_gpioiic0>; 117 scl-gpios = <&gpio1 5 GPIO_ACTIVE_HIGH>; 118 sda-gpios = <&gpio7 11 GPIO_ACTIVE_HIGH>; 119 status = "okay"; 120 121 /* One slave device on the i2c bus. */ 122 rtc@51 { 123 compatible="nxp,pcf2127"; 124 reg = <0x51>; 125 status = "okay"; 126 }; 127 }; 128}; 129.Ed 130.Pp 131Where: 132.Bl -tag -width ".Va compatible" 133.It Va compatible 134Should be set to "i2c-gpio". 135The deprecated string "gpioiic" is also accepted for backwards compatibility. 136.It Va scl-gpios Va sda-gpios 137These properties indicate which GPIO pins should be used for clock 138and data on the GPIO IIC bit-banging bus. 139There is no requirement that the two pins belong to the same gpio controller. 140.It Va pinctrl-names pinctrl-0 141These properties may be required to configure the chosen pins as gpio 142pins, unless the pins default to that state on your system. 143.El 144.Sh SEE ALSO 145.Xr fdt 4 , 146.Xr gpio 4 , 147.Xr iic 4 , 148.Xr iicbb 4 , 149.Xr iicbus 4 150.Sh HISTORY 151The 152.Nm 153manual page first appeared in 154.Fx 10.1 . 155.Sh AUTHORS 156This 157manual page was written by 158.An Luiz Otavio O Souza . 159