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32 .Nd GPIO I2C bit-banging device driver
34 To compile this driver into the kernel,
35 place the following lines in your
36 kernel configuration file:
37 .Bd -ragged -offset indent
44 Alternatively, to load the driver as a
45 module at boot time, place the following line in
47 .Bd -literal -offset indent
53 driver provides an IIC bit-banging interface using two GPIO pins for the
54 SCL and SDA lines on the bus.
57 simulates an open collector kind of output when managing the pins on the
58 bus, even on systems which don't directly support configuring gpio pins
60 The pins are never driven to the logical value of '1'.
61 They are driven to '0' or switched to input mode (Hi-Z/tri-state), and
62 an external pullup resistor pulls the line to the 1 state unless some
63 other device on the bus is driving it to 0.
64 .Sh HINTS CONFIGURATION
67 based system, such as MIPS, these values are configurable for
69 .Bl -tag -width ".Va hint.gpioiic.%d.atXXX"
70 .It Va hint.gpioiic.%d.at
74 Normally just gpiobus0 on systems with a single bank of gpio pins.
75 .It Va hint.gpioiic.%d.pins
76 This is a bitmask of the pins on the
78 that are to be used for SCLOCK and SDATA from the GPIO IIC
80 To configure pin 0 and 7, use the bitmask of
81 0b10000001 and convert it to a hexadecimal value of 0x0081.
82 Please note that this mask should only ever have two bits set
83 (any other bits - i.e., pins - will be ignored).
86 must be a child of the gpiobus, both gpio pins must be part of that bus.
87 .It Va hint.gpioiic.%d.scl
88 Indicates which bit in the
89 .Va hint.gpioiic.%d.pins
90 should be used as the SCLOCK
92 Optional, defaults to 0.
93 .It Va hint.gpioiic.%d.sda
94 Indicates which bit in the
95 .Va hint.gpioiic.%d.pins
96 should be used as the SDATA
98 Optional, defaults to 1.
100 .Sh FDT CONFIGURATION
103 based system, such as ARM, the DTS node for
105 conforms to the standard bindings document i2c/i2c-gpio.yaml.
106 The device node typically appears at the root of the device tree.
107 The following is an example of a
109 node with one slave device
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>;
121 /* One slave device on the i2c bus. */
123 compatible="nxp,pcf2127";
132 .Bl -tag -width ".Va compatible"
134 Should be set to "i2c-gpio".
135 The deprecated string "gpioiic" is also accepted for backwards compatibility.
136 .It Va scl-gpios Va sda-gpios
137 These properties indicate which GPIO pins should be used for clock
138 and data on the GPIO IIC bit-banging bus.
139 There is no requirement that the two pins belong to the same gpio controller.
140 .It Va pinctrl-names pinctrl-0
141 These properties may be required to configure the chosen pins as gpio
142 pins, unless the pins default to that state on your system.
153 manual page first appeared in
157 manual page was written by
158 .An Luiz Otavio O Souza .