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ADS111x(4) 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 ana- log to digital converter (ADC) devices. The supported devices are all sim- ilar 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). The sysctl(8) utility 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 sin- gle 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 mea- surement, 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 mea- surement would require 8 milliseconds. For devices that support multiple input pins, the device datasheet de- scribes mux settings to control how those pins are interpreted 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 combina- tions. 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 con- troller 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 reg- ister. 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 docu- ments eight available sample rates, chosen by setting a value of 0 through 7 into the corresponding control register bits. This vari- able 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 sam- ple; 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 micro- volts. Note that this variable does not appear when you list multiple sysctl variables -- you must access it specifically by name, be- cause 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 chan- nels 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 config- urable 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 speci- fied channels are created. SEE ALSO fdt(4), sysctl(8) HISTORY The ads111x driver first appeared in FreeBSD 13.0. FreeBSD ports 15.quarterly September 2, 2019 ADS111x(4)
NAME | SYNOPSIS | DESCRIPTION | SYSCTL VARIABLES | HARDWARE | FDT CONFIGURATION | HINTS CONFIGURATION | SEE ALSO | HISTORY
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