Add pyadi support for ADAQ4001 and ADAQ4003

[machschmitt]

Description

This PR adds pyadi support for ADAQ4001 and ADAQ4003.

AD4003/AD4007/AD4011, AD4020/AD4021/AD4022, and ADAQ4001/ADAQ4003 belong to a series of differential SAR ADC devices which are supported by the same Linux kernel driver.

This PR:

• Adds a python class for ADAQ4001 and ADAQ4003.
• Adds scale_available attribute to classes supporting AD4000 series devices.
• Adds iio-emu emulation model for ADAQ4003.
• Adds automated tests for ADAQ4003 class.
• Updates to ad4020 example so it works for other devices belonging to the AD4000 series.

Related JIRA task: https://jira.analog.com/browse/COSGTM-277

Type of change

• [x] New feature (non-breaking change which adds functionality)

How has this been tested?

• [x] Tested with iio-emu emulation model generated from ADAQ4003 device on Linux
• [x] Tested on CoraZ7 with Eval-ADAQ4003 and m2k+Scopy for input signal generation.

Test Configuration:

• Hardware: iio-emu model generated from a ADAQ4003 device running on Linux
• OS: Kuiper Linux

Documentation

The new python class was added to the list of documented classes provided by the ad4020 python module.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have signed off all commits and they contain "Signed-off by: "
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[thorenscientific]

@machschmitt the only other peculiarity I notice is that the sampling_frequency can only be set if there's no buffer created. That is, initially I can set the sample rate, but after calling rx(), attempting to set the sample rate throws: OSError: [Errno 16] Resource device Calling rx_destroy_buffer() allows the sample rate to be changed again. If this is expected behavior that's fine, just wondering if there's a cleaner way of handling it, either by calling rx_destroy_buffer() within the sampling_frequency setter, or just calling it in the example with a comment to the effect of: "can't set the sampling frequency if a buffer is created" (@tfcollins any thoughts?)

[tfcollins]

@machschmitt the only other peculiarity I notice is that the sampling_frequency can only be set if there's no buffer created. That is, initially I can set the sample rate, but after calling rx(), attempting to set the sample rate throws: OSError: [Errno 16] Resource device Calling rx_destroy_buffer() allows the sample rate to be changed again. If this is expected behavior that's fine, just wondering if there's a cleaner way of handling it, either by calling rx_destroy_buffer() within the sampling_frequency setter, or just calling it in the example with a comment to the effect of: "can't set the sampling frequency if a buffer is created" (@tfcollins any thoughts?)

The "nice" way to do this is with a decorator that manages it for you like so: https://github.com/analogdevicesinc/pyadi-iio/blob/main/adi/cn0540.py#L81

[machschmitt]

Updated according to suggestions. Regarding the voltage0-voltage-1 nomenclature, the devices can be set in Single-Ended to Differential Configuration, where they would sample like a single-ended ADC, and thus the channel type would be configurable. The current driver version does not support that but it may in the future, at which point, the interface would not reflect the channel type configuration if it is called just voltage0.

Change log v1 -> v2:

• replace match and case device selection (which were introduced only in Python 3.10) by cascaded if-else that are supported in Python >=3.7.
• Added reset_buffer convenience decorator to automatically disable the read buffer when a device configuration operation is issued.

[machschmitt]

I reverted the patch adding the reset_buffer convenience decorator because it was failing pytest and I am having trouble trying to run pytests with iio-emu locally. It looks like pytest is not starting iio-emu on my setup for it was failing with "Exception: No device found" and "Connection timed out".

The launch command was

pytest -vs --emu --emu-xml-dir=test/emu/devices/ --junitxml="results.xml" -k 'not prod' test/test_adaq4003.py

I updated and reinstalled libtinyiiod, iio-emu, and pyadi-iio, but the issue was not solved so I reverted the offending patch.