Problems in setting the trigger with lps22qs and iis2mdc sensors (magnetometer and barometer)

[Ginkgo]

I am trying to get the raw data (with timestamp included) from a few IIO devices (hardware sensors, such as accelerometer, gyroscope, magnetometer and barometer) mounted on a linux platform. I was able to get the data for the accelerometer and for the gyroscope using the libiio library within a C++ code (attached below). However, for the magnetometer and for the barometer it seems (I'm not expert in this field) they require (or have already set-up) some kind of trigger. For this reason the code I wrote cannot be used as it is for those two sensors. I do not need any trigger as I'd like just to get the flow of data without any "event" to start the logging. However I don't know if it's better to disable (if possible) the trigger or somehow to set it up in someway.

To make it more clear,

1. Here the result of the iio_info command (the devices of interest are ilps22qs and iis2mdc, respectively the barometer and the magnetometer). From here you can also see that for the magnetometer there's already (not set up by me) a trigger (iis2mdc-trigger).

Library version: 0.19 (git tag: v0.19)
Compiled with backends: local xml ip usb serial
IIO context created with local backend.
Backend version: 0.19 (git tag: v0.19)
Backend description string: Linux dab 5.4.193-toradex #1 SMP PREEMPT Fri Oct 6 13:55:59 CEST 2023 aarch64
IIO context has 1 attributes:
        local,kernel: 5.4.193-toradex
IIO context has 6 devices:
....
        iio:device1: ilps22qs (buffer capable)
                3 channels found:
                        pressure:  (input)
                        2 channel-specific attributes found:
                                attr  0: raw value: 4143498
                                attr  1: scale value: 0.000024414
                        temp:  (input)
                        2 channel-specific attributes found:
                                attr  0: raw value: 4278
                                attr  1: scale value: 10.000000000
                        timestamp:  (input, index: 2, format: le:S64/64>>0)
                5 device-specific attributes found:
                                attr  0: consumers ERROR: Input/output error (-5)
                                attr  1: current_timestamp_clock value: realtime

                                attr  2: sampling_frequency value: 1
                                attr  3: sampling_frequency_available value: 1 4 10 25 50 75 100 200
                                attr  4: suppliers ERROR: Input/output error (-5)
                2 buffer-specific attributes found:
                                attr  0: data_available value: 0
                                attr  1: watermark value: 1
        iio:device2: iis2mdc (buffer capable)
                4 channels found:
                        magn_x:  (input, index: 0, format: le:S16/16>>0)
                        3 channel-specific attributes found:
                                attr  0: raw ERROR: Device or resource busy (-16)
                                attr  1: scale value: 0.001500
                                attr  2: scale_available value: 0.001500
                        magn_y:  (input, index: 1, format: le:S16/16>>0)
                        3 channel-specific attributes found:
                                attr  0: raw ERROR: Device or resource busy (-16)
                                attr  1: scale value: 0.001500
                                attr  2: scale_available value: 0.001500
                        magn_z:  (input, index: 2, format: le:S16/16>>0)
                        3 channel-specific attributes found:
                                attr  0: raw ERROR: Device or resource busy (-16)
                                attr  1: scale value: 0.001500
                                attr  2: scale_available value: 0.001500
                        timestamp:  (input, index: 3, format: le:S64/64>>0)
                5 device-specific attributes found:
                                attr  0: consumers ERROR: Input/output error (-5)
                                attr  1: current_timestamp_clock value: realtime

                                attr  2: sampling_frequency value: 10
                                attr  3: sampling_frequency_available value: 10 20 50 100
                                attr  4: suppliers ERROR: Input/output error (-5)
                2 buffer-specific attributes found:
                                attr  0: data_available value: 16
                                attr  1: watermark value: 1
                Current trigger: trigger0(iis2mdc-trigger)
...
                                attr  1: watermark value: 1
        trigger0: iis2mdc-trigger
                0 channels found:
                2 device-specific attributes found:
                                attr  0: consumers ERROR: Input/output error (-5)
                                attr  1: suppliers ERROR: Input/output error (-5)

1. Trying to work from the linux terminal (sysfs), so for example enabling the buffer with "sudo echo 1 > buffer/enable" (and similar commands) for the magnetometer I am able to obtain the data but not the timestamp, while in the case of the barometer I am not even able to enable the buffer (it says "1" is a wrong argument for the "enable" file). So I do not know how these problems are linked with the trigger and how to resolve them.

I also already tried to deactivate the trigger for the barometer (see the code below), but it then says it is not able to create the buffer. Same thing if I do not deactivate the trigger. I recall  thatfor the barometer no trigger has been set-up, so maybe the problem is that I should create one instead of deactivating it... For the magnetometer I didn't try with the C++ code but from sysfs I was not able to get the timestamp and so I guess the problem will be the same if I try to work with the code.

So the questions are:

1. How can I get the "timestamp" for the magnometer?

2. How can I make the barometer work (data + timestamp)?

It's fine for me to work either from the linux terminal (sysfs) or with a C++ code.

Thanks in advance

trigger_device = iio_device_set_trigger(press_device, NULL);
    if (!trigger_device) {
        std::cerr << "Trigger not disabled" << std::endl;
        iio_context_destroy(ctx);
        return -1;
        }