ADS111x(4) FreeBSD Kernel Interfaces Manual ADS111x(4)
NAME
ads111x - driver for ADS101x and ADS111x i2c analog to digital converters
SYNOPSIS
To compile this driver into the kernel, place the following line in your
kernel configuration file:
device ads111x
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
ads111x_load="YES"
DESCRIPTION
The ads111x 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 sysctl(8).
Sysctl(8) provides access to the voltage measurements made by the device.
Each time the dev.ads111x.<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.
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 ads111x
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.
For devices that include an alert output pin, the ads111x 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.
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 loader(8) tunables. Channel numbers in these sysctl
variables range from 0 through 7.
dev.ads111x.<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.
dev.ads111x.<unit>.lo_thresh
Sets the low threshold for activating the alert pin.
dev.ads111x.<unit>.hi_thresh
Sets the high threshold for activating the alert pin.
dev.ads111x.<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.
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.
dev.ads111x.<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.
dev.ads111x.<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.
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.
HARDWARE
The ads111x driver provides support for the following devices:
ADS1013 ADS1113
ADS1014 ADS1114
ADS1015 ADS1115
FDT CONFIGURATION
On an fdt(4) based system, the ads111x device is defined as a slave
device subnode of the i2c bus controller node. All properties documented
in the ads1015.txt bindings document can be used with the ads111x device.
The following properties are required in the ads111x device subnode:
compatible
One of the following:
"ti,ads1013" "ti,ads1113"
"ti,ads1014" "ti,ads1114"
"ti,ads1015" "ti,ads1115"
reg I2c slave address of device.
Specific channels can be configured by adding child nodes to the ads111x
node, as described in the standard ads1015.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.
Example including channel configuration
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>;
};
};
HINTS CONFIGURATION
On a device.hints(5) based system, such as MIPS, these values are
configurable for ads111x:
hint.ads111x.<unit>.at
The iicbus instance the ads111x instance is attached to.
hint.ads111x.<unit>.<channel>.gain_index
The amplifier gain, as described above for the sysctl variable
dev.ads111x.<unit>.<channel>.gain_index.
hint.ads111x.<unit>.<channel>.rate_index
The sample rate, as described above for the sysctl variable
dev.ads111x.<unit>.<channel>.rate_index.
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.
SEE ALSO
fdt(4), sysctl(8)
HISTORY
The ads111x driver first appeared in FreeBSD 13.0.
FreeBSD 13.1-RELEASE-p6 September 2, 2019 FreeBSD 13.1-RELEASE-p6
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