Unfortunately, it still doesnt create the port. The last command returns:

I must add that I am trying to return the adapter and Im saving for a guider setup. Are there guider cameras I should stay away from due to compatibility issues? I read ZWO ASI120mm mini has issues with RPi4

As the device is a HID one, it will not enumerate as a serial port and won't create ttyACM* or ttyUSB* devices at all. ZWO SDK enumerates the device with libusb and communicates directly via HID messages. The driver should therefore "just work" if the user has sufficient permissions. The udev rule file installed by libasi package should handle that though so it would require a bit more debug logs from driver start to be able to see the issue.

Hello,

After 6 pages, this is the conclusion. The asi driver was attempted. It was not able to provide a working session. We did try a HID friendly rule. That did not work either.

ST4 communication is over an RJ-12 chord. That is 6 lines of serial talk. Looks serial to me. HID wants mice, keyboards, and other input devices.

This must be a marketing mistake. The price isn’t that bad. The use case seems to be missing.

I admire your patience! I would have returned the adapter the same week if it weren't for you.
Too bad it doesn't work, but I knew I could run into problems since it's not well documented.

Hopefully the communication between the guide camera and Pi will work better!

ST4 is actually just one on/off signal pin per direction (+-ra, +-dec) and ground, it doesn't have anything to do with serial communication as such. Also the computer communicates with a micro controller which handles the USB traffic, does timing of the guide pulses and so on, not directly to the ST4. Despite the name, HID is quite suitable for generic packet based communication with devices when the data amount is not very high as packets can be only up to 64 bytes long, but is more than enough for many applications with a simple command/response protocol. For example ZWO EAF focuser and Starlight Xpress filter wheel are HID devices as well. Rationale is that they are simpler to implement as operating systems have generic HID drivers and also communication is simpler without serial layer with all of its legacy in the middle.

I read this thread with great interest, thanks for sorting this out!

Using the ASI ST4 driver, I can connect to my LX50 and push guide signals. However, I cannot select it as a mount driver in PHD2 (Astroberry on RPi3). On my windows setup I could guide using the ZWO USBST4 ASCOM driver in the same setup. Is there any way to get PHD2 to use the ASI ST4 driver as a mount?

Thanks,
Oliver