Overview

The ASI120MC-S (and MM) have a strange behavior issue when the gain is changed during the day-night transitions. A few frames after the gain is changed, the camera experiences an exposure timeout.

Within the indi_asi code base, in asi_base.cpp, the indi server will try to transition the bit depth from 16-bit to 8-bit. This [temporarily] corrects the exposure issue, albeit, the camera now runs in 8-bit mode instead of 16-bit. Eventually, when the camera transitions from day/night later while in 8-bit mode, the camera will stop responding altogether.

Relevant code: https://github.com/indilib/indi-3rdparty/blob/master/indi-asi/asi_base.cpp#L249

The fix

indi-allsky has a bit of code to workaround this issue. Periodically (every ~3 minutes), indi-allsky will re-apply the INDI_CONFIG_DEFAULTS config options. When the code changes the gain, resulting in the camera transitioning to 8-bit mode, within 5 minutes, the INDI_CONFIG_DEFAULTS options will allow the camera to be put back into 16-bit mode.

INDI_CONFIG_DEFAULTS

The following config is necessary to force the camera back into 16-bit mode.

{
    "PROPERTIES": {},
    "SWITCHES": {
        "CCD_VIDEO_FORMAT": {
            "on": [
                "ASI_IMG_RAW16"
            ],
            "off": [
                "ASI_IMG_RAW8"
            ]
        }
    }
}