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Table of Contents
ADAS1000: Low Power, 5-ELECTRODE ELECTROCARDIOGRAM (ECG) ANALOG FRONT END (AFE) Linux Driver
Supported Devices
Evaluation Boards
Reference Circuits
Description
This is a Linux industrial I/O (IIO) subsystem driver, targeting multi 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.
Source Code
Status
| Source | Mainlined? |
|---|---|
| drivers/iio/adc/adas1000.c | In progress |
Files
| Function | File |
|---|---|
| driver | drivers/iio/adc/adas1000.c |
| include | include/linux/platform_data/adas1000.h |
Example platform device initialization
For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.
For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.
/** * struct adas1000_platform_data - ADAS1000 platform data * @enbale_vref_buffer: If true enable the vref buffer * @use_external_clock: If true use the external clock applied at the XTAL pin * @driver_external_common_mode: If true drive the internal common mode signal * to the external common mode pin. * @use_external_common_mode: If true use the signal applied at the external * common mode pin as the common mode signal. * @high_perfomance: If true configure the ADAS1000 for high performance mode. **/ struct adas1000_platform_data { bool enable_vref_buffer; bool use_external_clock; bool drive_external_common_mode; bool use_external_common_mode; bool high_performance; };
static struct adas1000_platform_data pdata { .enable_vref_buffer = true, .high_performance = true, };
If no platform data is provided the driver will use the device's default setting for all registers.
Declaring SPI slave devices
Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.
This method is appropriate when the SPI bus is a system bus, as in many embedded systems, wherein each SPI bus has a number which is known in advance. It is thus possible to pre-declare the SPI devices that inhabit this bus. This is done with an array of struct spi_board_info, which is registered by calling spi_register_board_info().
For more information see: Documentation/spi/spi-summary
Depending on the converter IC used, you may need to set the modalias accordingly, matching your part name. It may also required to adjust max_speed_hz. Please consult the datasheet, for maximum spi clock supported by the device in question.
static struct spi_board_info board_spi_board_info[] __initdata = { { .modalias = "adas1000", .max_speed_hz = 10000000, /* max spi clock (SCK) speed in HZ */ .bus_num = 0, .chip_select = GPIO_PF10 + MAX_CTRL_CS, /* CS, change it for your board */ .platform_data = &adas1000_pdata, .mode = SPI_MODE_0, }, };
static int __init board_init(void) { [--snip--] ? spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info)); ? [--snip--] ? return 0; } arch_initcall(board_init);
Adding Linux driver support
Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)
The ADAS1000 Driver depends on CONFIG_SPI
Linux Kernel Configuration Device Drivers ---> <*> Industrial I/O support ---> --- Industrial I/O support [--snip--] Analog to digital converters ---> *** Analog to digital converters *** [--snip--] <*> Analog Devices ADAS1000 ECG driver [--snip--]
Hardware configuration
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.
This specifies any shell prompt running on the target
root:/> cd /sys/bus/iio/devices/ root:/sys/bus/iio/devices> ls iio:device0 trigger0 root:/sys/bus/iio/devices> cd iio:device0 root:/sys/devices/platform/bfin-spi.0/spi0.12/iio:device0> ls -l drwxr-xr-x 2 root root 0 Jan 1 00:00 buffer -r--r--r-- 1 root root 4096 Jan 1 00:00 dev -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_filter_low_pass_3db_frequency -r--r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_filter_low_pass_3db_frequency_available -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_offset -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_sampling_frequency -r--r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_sampling_frequency_available -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_scale -r--r--r-- 1 root root 4096 Jan 1 00:00 in_voltage-voltage_scale_available -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage0-voltage2_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage0-voltage5_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage1-voltage0_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage1-voltage2_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage1-voltage5_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage2-voltage5_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage3-voltage5_calibscale -rw-r--r-- 1 root root 4096 Jan 1 00:00 in_voltage4-voltage5_calibscale -r--r--r-- 1 root root 4096 Jan 1 00:00 name -rw-r--r-- 1 root root 4096 Jan 1 00:00 out_voltage6_calibration_offset -rw-r--r-- 1 root root 4096 Jan 1 00:00 out_voltage6_calibration_powerdown -rw-r--r-- 1 root root 4096 Jan 1 00:00 out_voltage6_calibration_raw -rw-r--r-- 1 root root 4096 Jan 1 00:00 out_voltage6_calibration_scale drwxr-xr-x 2 root root 0 Jan 1 00:00 power -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_out_select -r--r--r-- 1 root root 4096 Jan 1 00:00 rld_out_select_available -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_powerdown -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_summing_junction_ce_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_summing_junction_la_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_summing_junction_ll_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_summing_junction_ra_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_summing_junction_v1_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 rld_summing_junction_v2_en drwxr-xr-x 2 root root 0 Jan 1 00:00 scan_elements -rw-r--r-- 1 root root 4096 Jan 1 00:00 shield_driver_powerdown lrwxrwxrwx 1 root root 0 Jan 1 00:00 subsystem -> ../../../../../../../bus/iio drwxr-xr-x 2 root root 0 Jan 1 00:00 trigger -rw-r--r-- 1 root root 4096 Jan 1 00:00 uevent -rw-r--r-- 1 root root 4096 Jan 1 00:00 vcm_summing_junction_ce_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 vcm_summing_junction_la_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 vcm_summing_junction_ll_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 vcm_summing_junction_ra_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 vcm_summing_junction_v1_en -rw-r--r-- 1 root root 4096 Jan 1 00:00 vcm_summing_junction_v2_en root:/sys/devices/platform/bfin-spi.0/spi0.12/iio:device0>
Show device name
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0/> cat name adas1000
Contains the device name, this will always be “adas1000” for the adas1000 driver.
List available low filter frequencies
Description:
in_voltage-voltage_filter_low_pass_3db_frequency_available
Lists all available low pass filter frequencies, which may be set by writing to in_voltage-voltage_filter_low_pass_3db_frequency.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_filter_low_pass_3db_frequency_available 40 150 250 400 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
Set and show low filter frequency
Description:
in_voltage-voltage_filter_low_pass_3db_frequency
Writing to this file will set the low pass filter frequency, reading from this file will show the currently selected low pass filter.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_filter_low_pass_3db_frequency 40 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 250 > in_voltage-voltage_filter_low_pass_3db_frequency root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_filter_low_pass_3db_frequency 250 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
The low pass filter will only be active when sampling with 2kHz base frequency.
List available sampling frequencies
Description:
in_voltage-voltage_sampling_frequency_available
Lists all available sampling frequencies, which may be set by writing to in_voltage-voltage_sampling_frequency.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_sampling_frequency_available 128000 64000 32000 16000 8000 4000 2000 1000 500 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
The only actuall supported sampling rates by the ADAS1000 are 128000, 16000 and 2000, all other sampling rates will be achieved by using a 2x or 4x decimation filter.
Set and show filter frequency
Description:
in_voltage-voltage_sampling_frequency
Writing to this file will set the sampling frequency, reading from the file will return the currently selected sampling frequency.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_sampling_frequency 4000 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
Setting a new sampling frequency can be done by writing to the file.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 8000 > in_voltage-voltage_sampling_frequency root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_sampling_frequency 8000 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
List available ADC gain values
Description:
in_voltage-voltage_scale_available
List the available ADC gain settings, which can be set using in_voltage-voltage_scale.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_scale_available 0.000019618 0.000013079 0.000009809 0.000006539 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
Set and ADC gain value
Description:
in_voltage-voltage_scale
Scale to be applied to in_voltageY-voltageZ_raw in order to obtain the measured voltage in millivolts.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_scale 0.000019618 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 0.000006539 > in_voltage-voltage_scale root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage-voltage_scale 0.000006539 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
Set ADC calibration gain
Description:
in_voltage0-voltage2_calibscale
in_voltage0-voltage5_calibscale
in_voltage1-voltage0_calibscale
in_voltage1-voltage2_calibscale
in_voltage1-voltage5_calibscale
in_voltage2-voltage5_calibscale
in_voltage3-voltage5_calibscale
in_voltage4-voltage5_calibscale
Set the channel calibration gain. Writing to these files will set the calibration gain for the respective channel. Valid values are in the range of -2048 to 2047.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 1020 > in_voltage0-voltage2_calibscale root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat in_voltage0-voltage2_calibscale 1020 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
in_voltage0-voltage2_calibscale and in_voltage0-voltage5_calibscale, in_voltage1-voltage0_calibscale and in_voltage1-voltage5_calibscale, in_voltage1-voltage2_calibscale and in_voltage2-voltage5_calibscale refer to the same set of calibration data.
List available Right Leg drive outputs
Description:
rld_out_select_available
List available values for the rld_out_select file.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat rld_out_select_available rl la ll ra v1 v2 root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
Select Right Leg drive output electrode
Description:
rld_out_select
Set the Right Leg drive output electrode.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo rl > rld_out_select_available root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat rld_out_select rl root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>
Enable/Disable Right Leg drive output
Description:
rld_powerdown
Enable or disable the Right Leg drive output. Writing a '0' to this file will enable the Right Leg drive, writing a '1' to this file will enable the Right Leg drive.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat rld_powerdown 1 root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> echo 0 > rld_powerdown root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat rld_powerdown 0
Setup Right Leg drive summing junction configuration
Description:
rld_summing_junction_ce_en
rld_summing_junction_la_en
rld_summing_junction_ll_en
rld_summing_junction_ra_en
rld_summing_junction_v1_en
rld_summing_junction_v2_en
Writing a '1' to a file will add the respective channel to the Right Leg driver summing junction, writing a '0' will remove it.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat rld_summing_junction_la_en 1 root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> echo 1 > rld_summing_junction_v2_en root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat rld_summing_junction_v2_en 1
Setup VCM summing junction configuration
Description:
vcm_summing_junction_ce_en
vcm_summing_junction_la_en
vcm_summing_junction_ll_en
vcm_summing_junction_ra_en
vcm_summing_junction_v1_en
vcm_summing_junction_v2_en
Writing a '1' to a file will add the respective channel to the VCM summing junction, writing a '0' will remove it.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat vcm_summing_junction_ra_en 0 root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> echo 1 > vcm_summing_junction_ra_en root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat vcm_summing_junction_ra_en 1
Enable/Disable shield driver
Description:
shield_driver_powerdown
Enable or disable the shield driver. Writing a '0' to this file will enable the shild driver, writing a '1' to this file will enable the shield driver.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat shield_driver_powerdown 1 root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> echo 0 > shield_driver_powerdown root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat shield_driver_powerdown 0
out_voltage6_calibration_offset
Enable/Disable calibration DAC
Description:
out_voltage6_calibration_powerdown
Enable or disable the calibration DAC. Writing a '0' to this file will enable the calibration DAC, writing a '1' to this file will disable the calibration DAC.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat out_voltage6_calibration_raw 1 root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> echo 0 > out_voltage6_calibration_powerdown root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat out_voltage6_calibration_raw 0
Set calibration DAC output value
Description:
out_voltage6_calibration_raw
Sets the calibration DAC output value. Valid values are in the range of 0-1023.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> echo 100 > out_voltage6_calibration_raw root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat out_voltage6_calibration_raw 100
Show calibration DAC scale
Description:
out_voltage6_calibration_scale
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0> cat out_voltage6_calibration_scale 0.002346
Vout = (out_voltage6_calibration_offset + out_voltage6_calibration_raw) * out_voltage6_calibration_scale
Debugfs
The adas1000 driver exposes also some files, which are meant for debugging purposes, in debugfs. These files can be used to read the OPSTAT register and to configure the testtone generator.
root:/sys/kernel/debug/iio/iio:device0> ls direct_reg_access pll_locked testtone_la_en testtone_v1_en fuse_crc_failure testtone_en testtone_ll_en testtone_v2_en fuse_status testtone_frequency testtone_out_en pll_lock_lost testtone_internal testtone_ra_en root:/sys/kernel/debug/iio/iio:device0>
Direct register read and write acccess
Description:
direct_reg_access
Allows direct register access to the device. To write to a register write the register address and the register value seperated by a space to the file.
This specifies any shell prompt running on the target
root:/sys/kernel/debug/iio/iio:device0> echo 0x12 0x17 > direct_reg_access
To read a register value, first write the register address to the file followed by a read.
This specifies any shell prompt running on the target
root:/sys/kernel/debug/iio/iio:device0> echo 0x05 > direct_reg_access root:/sys/kernel/debug/iio/iio:device0> cat direct_reg_access
Check fuse CRC status
Description:
fuse_crc_failure
'1' if a fuse CRC failure has been detected, '0' otherwise.
Check fuse status
Description:
fuse_status
'0' if the fuse bits have been read, '1' otherwise.
Check PLL status
Description:
pll_locked
'1' if the PLL is locked, '0' otherwise.
Enable testtone
Description:
testtone_en
Enable the testtone generator.
If both the testtone and the calibration DAC are enabled, the testtone will take precedence.
Set testtone frequnecy
Description:
testtone_frequency
Select the testtone frequency and waveform.
Valid values are:
- 1: 1 Hz square wave
- 10: 10 Hz sine wave
- 150: 150 Hz sine wave
Enable internal testtone routing
Description:
testtone_internal
Route the testtone signal internally ECG channels.
Enable external testtone output
Description:
testtone_out_en
Enables or disables testtone output to the external CAL_DAC_IO pin.
The testtone signal will be routed to the CAL_DAC_IO pin by default and only if internal routing is enabled this switch will have an effect.
Enable testtone routing to individual ECG channels
Description:
testtone_la_en
testtone_ll_en
testtone_ra_en
testtone_v1_en
testtone_v2_en
Enables the internal testtone routing to the individual ECG channels.
Trigger management
The adas1000 driver will register a IIO trigger for the device. The trigger will be hooked up to the devices DATARDY IRQ. Normally you would want to use this trigger as the trigger for the device.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0/> echo adas1000-dev0 > trigger/current_trigger root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0/> cat trigger/current_trigger adas1000-dev0
Buffer management
The Industrial I/O subsystem provides support for various ring buffer based data acquisition methods. Apart from device specific hardware buffer support, the user can chose between two different software ring buffer implementations. One is the IIO lock free software ring, and the other is based on Linux kfifo. Devices with buffer support feature an additional sub-folder in the /sys/bus/iio/devices/deviceX/ folder hierarchy. Called deviceX:bufferY, where Y defaults to 0, for devices with a single buffer.
Every buffer implementation features a set of files:
length
Get/set the number of sample sets that may be held by the buffer.
enable
Enables/disables the buffer. This file should be written last, after length and selection of scan elements.
watermark
A single positive integer specifying the maximum number of scan
elements to wait for.
Poll will block until the watermark is reached.
Blocking read will wait until the minimum between the requested
read amount or the low water mark is available.
Non-blocking read will retrieve the available samples from the
buffer even if there are less samples then watermark level. This
allows the application to block on poll with a timeout and read
the available samples after the timeout expires and thus have a
maximum delay guarantee.
data_available
A read-only value indicating the bytes of data available in the
buffer. In the case of an output buffer, this indicates the
amount of empty space available to write data to. In the case of
an input buffer, this indicates the amount of data available for
reading.
length_align_bytes
Using the high-speed interface. DMA buffers may have an alignment requirement for the buffer length.
Newer versions of the kernel will report the alignment requirements
associated with a device through the `length_align_bytes` property.
scan_elements
The scan_elements directory contains interfaces for elements that will be captured for a single triggered sample set in the buffer.
This specifies any shell prompt running on the target
root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0/scan_elements> ls in_voltage0-voltage2_en in_voltage1-voltage5_en in_voltage0-voltage2_index in_voltage1-voltage5_index in_voltage0-voltage2_type in_voltage1-voltage5_type in_voltage0-voltage5_en in_voltage2-voltage5_en in_voltage0-voltage5_index in_voltage2-voltage5_index in_voltage0-voltage5_type in_voltage2-voltage5_type in_voltage1-voltage0_en in_voltage3-voltage5_en in_voltage1-voltage0_index in_voltage3-voltage5_index in_voltage1-voltage0_type in_voltage3-voltage5_type in_voltage1-voltage2_en in_voltage4-voltage5_en in_voltage1-voltage2_index in_voltage4-voltage5_index in_voltage1-voltage2_type in_voltage4-voltage5_type root:/sys/devices/platform/bfin-spi.0/spi_master/spi0/spi0.18/iio:device0/scan_elements>
| Channel | Function |
|---|---|
| in_voltage0-voltage2 | LA-RA (LEAD I) |
| in_voltage1-voltage0 | LL-LA (LEAD II) |
| in_voltage1-voltage2 | LL-RA (LEAD III) |
| in_voltage0-voltage5 | LA-VCM |
| in_voltage1-voltage5 | LL-VCM |
| in_voltage2-voltage5 | RA-VCM |
| in_voltage3-voltage5 | V1-VCM (V1') |
| in_voltage4-voltage5 | V2-VCM (V2') |
If any of the first three channels is selected the device will operate in Lead mode, otherwise it will operate in single-end mode. If channels from the first three channels are selected channels from the second three channels can not be selected and vice versa.
in_voltageX_en / in_voltageX-voltageY_en / timestamp_en:
Scan element control for triggered data capture.
Writing 1 will enable the scan element, writing 0 will disable it
in_voltageX_type / in_voltageX-voltageY_type / timestamp_type:
Description of the scan element data storage within the buffer
and therefore in the form in which it is read from user-space.
Form is [s|u]bits/storage-bits. s or u specifies if signed
(2's complement) or unsigned. bits is the number of bits of
data and storage-bits is the space (after padding) that it
occupies in the buffer. Note that some devices will have
additional information in the unused bits so to get a clean
value, the bits value must be used to mask the buffer output
value appropriately. The storage-bits value also specifies the
data alignment. So u12/16 will be a unsigned 12 bit integer
stored in a 16 bit location aligned to a 16 bit boundary.
For other storage combinations this attribute will be extended
appropriately.
in_voltageX_index / in_voltageX-voltageY_index / timestamp_index:
A single positive integer specifying the position of this
scan element in the buffer. Note these are not dependent on
what is enabled and may not be contiguous. Thus for user-space
to establish the full layout these must be used in conjunction
with all _en attributes to establish which channels are present,
and the relevant _type attributes to establish the data storage
format.
More Information
- IIO mailing list: linux [dash] iio [at] vger [dot] kernel [dot] org
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