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.Pp 65.Sh HINTS CONFIGURATION 66On a 67.Xr device.hints 5 68based system, such as MIPS, these values are configurable for 69.Nm : 70.Bl -tag -width ".Va hint.gpioiic.%d.atXXX" 71.It Va hint.gpioiic.%d.at 72The 73.Nm gpiobus 74you are attaching to. 75Normally just gpiobus0 on systems with a single bank of gpio pins. 76.It Va hint.gpioiic.%d.pins 77This is a bitmask of the pins on the 78.Nm gpiobus 79that are to be used for SCLOCK and SDATA from the GPIO IIC 80bit-banging bus. 81To configure pin 0 and 7, use the bitmask of 820b10000001 and convert it to a hexadecimal value of 0x0081. 83Please note that this mask should only ever have two bits set 84(any other bits - i.e., pins - will be ignored). 85Because 86.Nm 87must be a child of the gpiobus, both gpio pins must be part of that bus. 88.It Va hint.gpioiic.%d.scl 89Indicates which bit in the 90.Va hint.gpioiic.%d.pins 91should be used as the SCLOCK 92source. 93Optional, defaults to 0. 94.It Va hint.gpioiic.%d.sda 95Indicates which bit in the 96.Va hint.gpioiic.%d.pins 97should be used as the SDATA 98source. 99Optional, defaults to 1. 100.El 101.Sh FDT CONFIGURATION 102On an 103.Xr FDT 4 104based system, such as ARM, the DTS node for 105.Nm gpioiic 106conforms to the standard bindings document i2c/i2c-gpio.yaml. 107The device node typically appears at the root of the device tree. 108The following is an example of a 109.Nm 110node with one slave device 111on the IIC bus: 112.Bd -literal 113/ { 114 gpioiic0 { 115 compatible = "i2c-gpio"; 116 pinctrl-names = "default"; 117 pinctrl-0 = <&pinctrl_gpioiic0>; 118 scl-gpios = <&gpio1 5 GPIO_ACTIVE_HIGH>; 119 sda-gpios = <&gpio7 11 GPIO_ACTIVE_HIGH>; 120 status = "okay"; 121 122 /* One slave device on the i2c bus. */ 123 rtc@51 { 124 compatible="nxp,pcf2127"; 125 reg = <0x51>; 126 status = "okay"; 127 }; 128 }; 129}; 130.Ed 131.Pp 132Where: 133.Bl -tag -width ".Va compatible" 134.It Va compatible 135Should be set to "i2c-gpio". 136The deprecated string "gpioiic" is also accepted for backwards compatibility. 137.It Va scl-gpios Va sda-gpios 138These properties indicate which GPIO pins should be used for clock 139and data on the GPIO IIC bit-banging bus. 140There is no requirement that the two pins belong to the same gpio controller. 141.It Va pinctrl-names pinctrl-0 142These properties may be required to configure the chosen pins as gpio 143pins, unless the pins default to that state on your system. 144.El 145.Sh SEE ALSO 146.Xr fdt 4 , 147.Xr gpio 4 , 148.Xr iic 4 , 149.Xr iicbb 4 , 150.Xr iicbus 4 151.Sh HISTORY 152The 153.Nm 154manual page first appeared in 155.Fx 10.1 . 156.Sh AUTHORS 157This 158manual page was written by 159.An Luiz Otavio O Souza . 160