The most recent version of this page is a draft.
This version (01 Feb 2019 10:04) was approved by Stefan Popa.The Previously approved version (16 Oct 2018 11:29) is available.
百度 从那以后，国际经济研究界就不断使用这一概念，但很少有人去认真研究这里面都讲了什么，更鲜有人真正弄明白这里面是否有猫腻。
This version (01 Feb 2019 10:04) was approved by Stefan Popa.The Previously approved version (16 Oct 2018 11:29) is available.This is an old revision of the document!
Table of Contents
AD7124 IIO Sigma-Delta ADC Linux Driver
Supported Devices
Evaluation Boards
Description
This is a Linux industrial I/O (IIO) subsystem driver, targeting single channel serial interface ADCs. The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). See IIO for more information.
Status
Files
| Function | File |
|---|---|
| driver | drivers/iio/adc/ad7124.c |
| devicetree bindings | Documentation/devicetree/bindings/iio/adc/adi,ad7124.txt |
Driver testing
Each and every IIO device, typically a hardware chip, has a device folder under /sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under every of these directory folders reside a set of files, depending on the characteristics and features of the hardware device in question. These files are consistently generalized and documented in the IIO ABI documentation. In order to determine which IIO deviceX corresponds to which hardware device, the user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case the sequence in which the iio device drivers are loaded/registered is constant, the numbering is constant and may be known in advance.
TIP: An example program which uses the interface can be found here:
This specifies any shell prompt running on the target
root:/> cd /sys/bus/iio/devices/ root:/sys/bus/iio/devices> ls iio:device0 root:/sys/bus/iio/devices> cd iio\:device0 root:/sys/bus/iio/devices/iio:device0> ls -l drwxr-xr-x 2 root root 0 Jun 23 21:46 buffer -r--r--r-- 1 root root 4096 Jun 23 21:46 dev -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage0-voltage1_offset -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage0-voltage1_raw -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage0-voltage1_sampling_frequency -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage0-voltage1_scale -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage2-voltage3_offset -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage2-voltage3_raw -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage2-voltage3_sampling_frequency -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage2-voltage3_scale -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage4-voltage5_offset -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage4-voltage5_raw -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage4-voltage5_sampling_frequency -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage4-voltage5_scale -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage6-voltage7_offset -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage6-voltage7_raw -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage6-voltage7_sampling_frequency -rw-r--r-- 1 root root 4096 Jun 23 21:46 in_voltage6-voltage7_scale -r--r--r-- 1 root root 4096 Jun 23 21:46 name lrwxrwxrwx 1 root root 0 Jun 23 21:46 of_node -> ../../../../../../../../firmware/devicetree/base/soc/spi@7e204000/ad7124-4@0 drwxr-xr-x 2 root root 0 Jun 23 21:46 power drwxr-xr-x 2 root root 0 Jun 23 21:46 scan_elements lrwxrwxrwx 1 root root 0 Jun 23 21:46 subsystem -> ../../../../../../../../bus/iio drwxr-xr-x 2 root root 0 Jun 23 21:46 trigger -rw-r--r-- 1 root root 4096 Jun 23 21:46 uevent
Show device name
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat name ad7124-4
Show channel scale and offset
Description:
Scales and offsets to be applied to in_voltagex_voltagey_raw in order to obdatin the measured voltage in millivolts
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat in_voltage0-voltage1_scale 0.000149011 root:/sys/bus/iio/devices/iio:device0> cat in_voltage0-voltage1_offset 0 root:/sys/bus/iio/devices/iio:device0> cat in_voltage0-voltage1_raw 2679470
Description:
Channel Ainp0-Ainm1 is configured as unipolar, with a gain of 1
U = in_voltage0-voltage1_raw * in_voltage0-voltage1_scale - in_voltage0-voltage1_offset = 2679470 * 0.000149011 - 0 = 399.27 mV
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat in_voltage2-voltage3_scale 0.000298023 root:/sys/bus/iio/devices/iio:device0> cat in_voltage2-voltage3_offset -2500 root:/sys/bus/iio/devices/iio:device0> cat in_voltage2-voltage3_raw 9716211
Description:
Channel Ainp2-Ainm3 is configured as bipolar, with a gain of 1
U = in_voltage2-voltage3_raw * in_voltage2-voltage3_scale - in_voltage2-voltage3_offset = 9716211* 0.000298023 - 2500= 395.65 mV
Set sampling frequency
Description:
The output data rate depends on the master clock frequency (fclk) which in turn determines the power mode:
- Full power (fCLK = 614.4 kHz): 9.38 SPS to 19,200 SPS
- Mid power (fCLK = 153.6 kHz): 2.34 SPS to 4800 SPS
- Low power (fCLK = 76.8 kHz): 1.17 SPS to 2400 SPS
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat in_voltage0-voltage1_sampling_frequency 10 root:/sys/bus/iio/devices/iio:device0> cat in_voltage2-voltage3_sampling_frequency 960 root:/sys/bus/iio/devices/iio:device0> echo 2400 > in_voltage0-voltage1_sampling_frequency root:/sys/bus/iio/devices/iio:device0> cat in_voltage0-voltage1_sampling_frequency 2400 root:/sys/bus/iio/devices/iio:device0> echo 5000 > in_voltage2-voltage3_sampling_frequency root:/sys/bus/iio/devices/iio:device0> cat in_voltage2-voltage3_sampling_frequency 4800
More Information
- IIO mailing list: linux [dash] iio [at] vger [dot] kernel [dot] org
/srv/wiki.analog.com/data/pages/resources/tools-software/linux-drivers/iio-adc/ad7124.txt · Last modified: 16 May 2024 18:24 by David Lechner