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authorIan Lepore <ian@FreeBSD.org>2019-08-05 15:56:44 +0000
committerIan Lepore <ian@FreeBSD.org>2019-08-05 15:56:44 +0000
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parent403c9d52eb56d2187621f8f403c1945056b84de0 (diff)
downloadsrc-5177d2941a48ee425aace573e9c7cc8ad144493b.tar.gz
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Add a driver for Texas Instruments ADS101x/ADS111x i2c ADC chips.
Instances of the device can be configured using hints or FDT data. Interfaces to reconfigure the chip and extract voltage measurements from it are available via sysctl(8).
Notes
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+.\"
+.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org>
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\"
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd August 5, 2019
+.Dt ADS1115 4
+.Os
+.Sh NAME
+.Nm ads1115
+.Nd driver for ADS101x and ADS111x i2c analog to digital converters
+.Sh SYNOPSIS
+To compile this driver into the kernel,
+place the following line in your
+kernel configuration file:
+.Bd -ragged -offset indent
+.Cd "device ads1115"
+.Ed
+.Pp
+Alternatively, to load the driver as a
+module at boot time, place the following line in
+.Xr loader.conf 5 :
+.Bd -literal -offset indent
+ads1115_load="YES"
+.Ed
+.Sh DESCRIPTION
+The
+.Nm
+driver provides support for the ADS101x/ADS111x family of analog
+to digital converter (ADC) devices.
+The supported devices are all similar to each other, varying in
+features such as resolution and number of input channels.
+The devices offer a number of configuration options which can be
+set via hints, FDT data, and
+.Xr sysctl 8 .
+.Pp
+.Xr Sysctl 8
+provides access to the voltage measurements made by the device.
+Each time the
+.Va dev.ads1115.<unit>.<channel>.voltage
+variable is accessed for a given channel, the driver switches the
+chip's internal mux to choose the right input pins for that channel,
+directs it to make a single measurement, and returns the measured value
+in microvolts.
+The amount of time required to make the measurement is a function
+of the sampling rate configured for the device.
+While device is directed to make a single measurement, it still averages
+the input values for the same amount of time as it would to emit one
+sample if it were in continuous mode.
+For example, if the sample rate were configured as 125 samples per
+second, a single measurement would require 8 milliseconds.
+.Pp
+For devices that support multiple input pins, the device datasheet
+describes mux settings to control how those pins are interpeted when
+making either single-ended or differential measurements.
+There are eight possible ways to combine the inputs from the four pins.
+The
+.Nm
+driver models that by creating a separate output channel for each of
+the eight combinations.
+To make a measurement on a given pin or pair of pins, you simply access
+the voltage variable for the channel number that corresponds the mux
+setting number (0 through 7) shown in the datasheet.
+When the driver is configured with hints or FDT data, it creates
+sysctl variables for just the channels specified in the config data.
+When there is no channel config data, it creates all eight possible
+channels so that you can access whichever one(s) you need.
+.Pp
+For devices that include an
+.Va alert
+output pin, the
+.Nm
+driver does not directly support the pin in terms of sensing or
+acting on changes in the pin state.
+However, you may connect the pin to a gpio input or fan controller
+or other external device, and use the driver's sysctl variables to
+configure behavior and threshold values for the pin.
+The driver avoids perturbing your settings as it does other
+manipulations to the config register.
+.Sh SYSCTL VARIABLES
+Sysctl variables are used to access the voltage measurements, and to
+change the configuration of the channels.
+All writeable variables may also be set as
+.Xr loader 8
+tunables.
+Channel numbers in these sysctl variables range from 0 through 7.
+.Bl -tag -width indent
+.It Va dev.ads1115.<unit>.config
+Provides access to the configuration register bits that control the
+alert pin configuration.
+Other bits which are controlled by the driver are masked out, and
+cannot be viewed or changed using this variable.
+.It Va dev.ads1115.<unit>.lo_thresh
+Sets the low threshold for activating the alert pin.
+.It Va dev.ads1115.<unit>.hi_thresh
+Sets the high threshold for activating the alert pin.
+.It Va dev.ads1115.<unit>.<channel>.rate_index
+Sets the sample rate for the channel.
+The device datasheet documents eight available sample rates, chosen
+by setting a value of 0 through 7 into the corresponding control
+register bits.
+This variable sets the value used for those bits when making a
+measurement on the given channel.
+.Pp
+Because measurements are always made in single-shot mode, think of
+this variable as controlling the averaging time for a single sample;
+the time to make a measurement is 1 / samplerate.
+.It Va dev.ads1115.<unit>.<channel>.gain_index
+Sets the programmable gain amplifier for the channel on devices
+which have an internal amplifier.
+The device datasheet documents eight available gain values, chosen
+by setting a value of 0 through 7 into the corresponding control
+register bits.
+This variable sets the value used for those bits when making a
+measurement on the given channel.
+.It Va dev.ads1115.<unit>.<channel>.voltage
+Reading this variable causes the device to make a measurement on
+the corresponding input pin(s) and return the voltage in microvolts.
+.Pp
+Note that this variable does not appear when you list multiple
+sysctl variables -- you must access it specifically by name, because
+accessing it triggers device I/O.
+.El
+.Sh HARDWARE
+The
+.Nm
+driver provides support for the following devices:
+.Pp
+.Bl -column -compact -offset indent "XXXXXXXX" "XXXXXXXX"
+.It ADS1013 Ta ADS1113
+.It ADS1014 Ta ADS1114
+.It ADS1015 Ta ADS1115
+.El
+.Sh FDT CONFIGURATION
+On an
+.Xr fdt 4
+based system, the
+.Nm
+device is defined as a slave device subnode
+of the i2c bus controller node.
+All properties documented in the
+.Va ads1115.txt
+bindings document can be used with the
+.Nm
+device.
+.Pp
+The following properties are required in the
+.Nm
+device subnode:
+.Bl -tag -width indent
+.It Va compatible
+One of the following:
+.Bl -column -compact -offset indent ".Dq ti,ads1013" ".Dq ti,ads1113"
+.It Dq ti,ads1013 Ta Dq ti,ads1113
+.It Dq ti,ads1014 Ta Dq ti,ads1114
+.It Dq ti,ads1015 Ta Dq ti,ads1115
+.El
+.It Va reg
+I2c slave address of device.
+.El
+.Pp
+Specific channels can be configured by adding child nodes to the
+.Nm
+node, as described in the standard ads1115.txt bindings document.
+If no channels are configured, sysctl variables will be created
+for all possible channels supported by the device type, otherwise
+only the specified channels are created.
+.Ss Example including channel configuration
+.Bd -unfilled -offset indent
+adc@48 {
+ compatible = "ti,ads1115";
+ reg = <0x48>;
+ status = "okay";
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ channel@6 {
+ reg = <6>;
+ ti,gain = <3>;
+ ti,datarate = <4>;
+ };
+ channel@7 {
+ reg = <7>;
+ ti,gain = <1>;
+ ti,datarate = <7>;
+ };
+};
+.Ed
+.Sh HINTS CONFIGURATION
+On a
+.Xr device.hints 5
+based system, such as
+.Li MIPS ,
+these values are configurable for
+.Nm :
+.Bl -tag -width indent
+.It Va hint.ads1115.<unit>.at
+The iicbus instance the
+.Nm
+instance is attached to.
+.It Va hint.ads1115.<unit>.<channel>.gain_index
+The amplifier gain, as described above for the sysctl variable
+.Va dev.ads1115.<unit>.<channel>.gain_index .
+.It Va hint.ads1115.<unit>.<channel>.rate_index
+The sample rate, as described above for the sysctl variable
+.Va dev.ads1115.<unit>.<channel>.rate_index .
+.El
+.Pp
+If no channels are configured, sysctl variables will be created
+for all possible channels supported by the device type, otherwise
+only the specified channels are created.
+.Sh SEE ALSO
+.Xr fdt 4 ,
+.Xr sysctl 4
+.Sh HISTORY
+The
+.Nm
+driver first appeared in
+.Fx 13.0 .