| ADS111x(4) | Device Drivers Manual | ADS111x(4) |
ads111x — driver
for ADS101x and ADS111x i2c analog to digital converters
To compile this driver into the kernel, place the following line in your kernel configuration file:
device ads111xAlternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
ads111x_load="YES"
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 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.
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.
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.
The ads111x driver provides support for
the following devices:
| ADS1013 | ADS1113 |
| ADS1014 | ADS1114 |
| ADS1015 | ADS1115 |
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:
| “ti,ads1013” | “ti,ads1113” |
| “ti,ads1014” | “ti,ads1114” |
| “ti,ads1015” | “ti,ads1115” |
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.
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>;
};
};
On a device.hints(5) based system, such as
MIPS, these values are configurable for
ads111x:
ads111x instance is
attached to.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.
The ads111x driver first appeared in
FreeBSD 13.0.
| September 2, 2019 | Debian |