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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.
65 .Sh HINTS CONFIGURATION
68 based system, such as MIPS, these values are configurable for
70 .Bl -tag -width ".Va hint.gpioiic.%d.atXXX"
71 .It Va hint.gpioiic.%d.at
75 Normally just gpiobus0 on systems with a single bank of gpio pins.
76 .It Va hint.gpioiic.%d.pins
77 This is a bitmask of the pins on the
79 that are to be used for SCLOCK and SDATA from the GPIO IIC
81 To configure pin 0 and 7, use the bitmask of
82 0b10000001 and convert it to a hexadecimal value of 0x0081.
83 Please note that this mask should only ever have two bits set
84 (any other bits - i.e., pins - will be ignored).
87 must be a child of the gpiobus, both gpio pins must be part of that bus.
88 .It Va hint.gpioiic.%d.scl
89 Indicates which bit in the
90 .Va hint.gpioiic.%d.pins
91 should be used as the SCLOCK
93 Optional, defaults to 0.
94 .It Va hint.gpioiic.%d.sda
95 Indicates which bit in the
96 .Va hint.gpioiic.%d.pins
97 should be used as the SDATA
99 Optional, defaults to 1.
101 .Sh FDT CONFIGURATION
104 based system, such as ARM, the DTS node for
106 conforms to the standard bindings document i2c/i2c-gpio.yaml.
107 The device node typically appears at the root of the device tree.
108 The following is an example of a
110 node with one slave device
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>;
122 /* One slave device on the i2c bus. */
124 compatible="nxp,pcf2127";
133 .Bl -tag -width ".Va compatible"
135 Should be set to "i2c-gpio".
136 The deprecated string "gpioiic" is also accepted for backwards compatibility.
137 .It Va scl-gpios Va sda-gpios
138 These properties indicate which GPIO pins should be used for clock
139 and data on the GPIO IIC bit-banging bus.
140 There is no requirement that the two pins belong to the same gpio controller.
141 .It Va pinctrl-names pinctrl-0
142 These properties may be required to configure the chosen pins as gpio
143 pins, unless the pins default to that state on your system.
154 manual page first appeared in
158 manual page was written by
159 .An Luiz Otavio O Souza .