Over the last few weeks I've been exploring the feasibility of using Ekos in Raspberry Pi to control my Fujifilm GFX 50SII.
It has involved a lot of trial and error, so I thought that it would be worth documenting some of my findings.

Camera setup - prior to connecting the camera to my RPi, I set the following:
a. Turn off all power saver options – otherwise exposures longer than 60 sec won’t download;
b. Set viewfinder to EVF only + eye – turns off all display unless you put your eye to the viewfinder, reducing camera battery load;
c. Set Connection mode to USB Tether Shooting Auto
d. Set the shutter to EFC, the dial wheel to manual, and exposure length to ‘Bulb’;
e. Connect the camera to the RPi and turn it on followed by a powerup of the Pi.

Once the RPi is powered up and I've connected to it via the browser on my desktop, I fire up KStars, then Ekos and initiate the camera connection using the Fuji camera driver. Configuring this was quite a hassle, in particular getting the camera to take 16-bit rather than 8-bit images - taking a FITS format file shifted it into 16-bit mode, and that setting is now saved in my configuration and gets applied to raw format files as well.
Other INDI settings that seem to work are as follows:
a. Indi option set to FORCE BULB = ON - enables longer exposure lengths that sit between Fuji's rather large exposure steps, i.e., other than 1/2/4/8/15 and 30 minutes - the exposure is reported as the closest of these in Lightroom, but checking the EXIF in RawDigger, the actual shutter open length is accurately recorded;
b. I've not found a way to save images to the camera SD card, and reading between the lines in the camera manual, I don't think that it’s possible with the camera in this connection mode - as a consequence I set the SD image parameter in the INDI image tab to 'DELETE';

On the EKOS camera control tab I do the following:
a. Manually set any exposure length and number of exposures;
b. Set file format to RAW and Native;
c. Under file settings I select Save = Locally and explicitly select the destination folder - if I don't manually navigate to the desired folder on the RPi where I want the files stored, it is sometimes unable to locate the default directory shown at startup;
d. Leave the delay set to 0;
e. Unless I want to inspect each file, I disable the option 'Use FITS viewer' under the FITS viewer tab of the EKOS options dialogue (bottom right of the EKOS camera dialogue) - if I don't do this, the reported file download times sometimes approach 30 seconds per file - from what I can work out, this is not the amount of time taken for the file to download, but the combined time taken to download the file and to reformat it to allow display in the FITS viewer. When I have the viewer disabled, average download times are around 2.5 seconds. I find I can turn the FITS viewer on and off in between images if I want to check progress.

This overall setup was initially quite unstable, but whenever I fixed a problem, I saved my configuration in the Options tab of the INDI control panel, and now reload that configuration each time I start up a new session.
I was concerned that the setup might become unstable during a session, but have just successfully run a trial session taking 150 minutes of exposures (inside) in a mix of exposure lengths from 11 to 450 seconds, with all images saved onto the RPi, and subsequently downloaded to my desktop with FileZilla where I imported and checked them in LR and with RawDigger. This exhausted the camera battery, but the 10,000 mAhr momax powerbank I was using to power the RPi was only half discharged.
I would be interested to know if anyone else is playing in this space and whether you've found a way to save to the SD card.
Regards
John

Hi John,
I'm a Fuji kstars imager. Having to set SDCard to Delete is a long standing known limitation. In fact I patched the Indi Fuji implementation to allow saving of that setting in the config.
The other issues I've run into are: aborting a capture can leave the frame in the buffer - the only way to recover if it does is to stop the indi server and power cycle the camera; If the GFX 50SII uses the same autofocus technology as the smaller XTrans sensors you may have an offset region on your calibration frames that needs to be correctly handled when stacking. Siril can take care of this but I don't know about other stacking software.
Regards
Ed

Thank you John & Ed for the reports. If you can submit any fixes to the INDI GPhoto driver that would be great. Otherwise, we can simply update the documentation to reflect these limitations.

My one line change was merged in for the INDI Library v1.9.5 release. I don't think there's anything else to be done in INDI - I wouldn't change the default or enforce the SDCard Delete due to the limited testing and the potential for Fuji to change the behaviour for future models.

It would be useful to document driver quirks / specific configuration requirements so that new users don't have to 're-invent the wheel' but where would be best for this? The KStars Handbook is the most user accessible place but doesn't contain any device documentation (correctly in my opinion). Upstream for the driver may be ideologically best which would be at github.com/gphoto/libgphoto2/tree/master/camlibs/fuji but then this is really hard for users to find and the content, style & maintenance is down to others, so maybe it should be at github.com/indilib/indi-3rdparty/tree/master/indi-gphoto ?

Maybe we could add a few links to INDI driver documentation in the 7.7 INDI Frequently Asked Questions section of the KStars Handbook? The trouble is that INDI driver documentation is non-existent for many of the drivers and depends entirely on the developer. I feel that this is one area that limits adoption of the whole INDI ecosystem for non-technical users. I don't know what the solution to that would look like - maybe more user guide / workflow style documentation for INDI drivers? This could be a large undertaking but maybe a format template and a few simple example cases would be a good start?

Thoughts / opinions?

The official driver documentation is here: indilib.org/individuals/devices/cameras/gphoto.html

I already added link before to a Fuji HOWTO. If that's outdated and we need a new one, we can put another link there if you can consolidate all the information in one topic.

My apologies, I hadn't found that information. I'll look at consolidating all of it - I have some X-T2 specific points as well.

Thanks for the responses, and interesting to hear your experience, Ed. My post was motivated by seeing a couple of other queries from folk enquiring about use of a GFX camera, and I figured that it was best to get at least something searchable on-line. My sense is that writing any definitive Fuji documentation is made difficult by the variation across different models, and the possibility that Fuji might change setups both between cameras and in firm-ware updates. I've tried my Fuji X-E3 with the Raspberry Pi, but it seems to be a no-go, because it lacks the USB connection option required for linking. I think that I'm too much of a novice to be suggesting changes in the driver, Jasem, but will keep that in mind as I get more experience with my setup.

Ed, I've not had issues with the focus zone on the GFX 50SII, but I process with bias, darks, and flats in PI, which I imagine would take care of it if its there. It might be more of an issue with the GFX100 which has phase detection.

John