Thank you Rob, and it would indeed be a great help if we collect the various combinations that work (and don't work) in the documentation. The outcomes will probably be different for the different devices, so perhaps the most logical place would be to add it to the individual drivers INDI-page.
It seems like there are several variables that are relevant:
- the USB to Serial bridge controller chip in the device (focuser, USB>Serial cable, etc)
- the version of the virtual com-port driver (the brand is determined by the chip)
- the macOS version
As far as chips and drivers go, the three main brands that keep coming up are: Prolific, FTDI and Silabs
As far as macOS version is concerned this may be limited to: before Big Sur vs Big Sur and later.
The drivers use system extensions. Before Big Sur these were Kernel extensions, using little system files with the extension .kext. In Catalina so called driver extensions were introduced, making use of DriverKit. Kernel extensions require terminal commands to install and normally you won't see them. Driver extensions install as an app and remain visible as an app in the Applications folder. Catalina introduced Driver extensions. From Big Sur onwards, this was mandatory.
so perhaps we can add an extra line with each INDI driver for which we have the information.

For the Sesto Senso 2 and Esatto focusers this could look like:
For this INDI driver to work properly on a Mac, a separate USB-Serial driver needs to be installed. The legacy Silabs driver version 4.* can be found here . Installation requires macOS 10.14 (Catalina) or lower. So far, it has not been possible to establish a proper connection using either driver version 6.* or macOS 11 (Big Sur) and higher.

For the Microtouch focuser (based on another thread on this topic), it could look like:
For this INDI driver to work properly on a Mac, a separate USB-Serial driver needs to be installed. The latest Silabs driver can be found here . This driver has shown to work on macOS 12 (Monterey) and is likely to work on 10.14 (Catalina) and 11 (Big Sur). For older macOS version, the legacy Silabs driver may be required, which can be found here .  

Even so, it would be good to know from people who have no problems with focusers and their Macs, for which it could look like:
For this INDI driver to work properly on a Mac, no separate USB-Serial drivers need to be installed. The required drivers are embedded in the macOS. This has been tested on macOS versions .....

Finally it looks like most issues occur with focusers and USB-Serial cables, but perhaps there are other devices as well? USB-serial cables probably have an infinite amount of manufacturers. But they probably all use one of the three chips. Perhaps we could create a general sentence on USB-serial cables, and point people to the three drivers mentioned. We could add that sentence to the devices that have a traditional serial (DB-9?) interface.

Just a few thoughts, Rob. Happy to help further where I can. I've got a Monterey and Mojave setup that I can use. But only have the Primalucelab focusers as hardware that I can test.

Willem Jan.

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