Rescan USB Serial Converter?

bvch291 wrote:

Hello, I am doing some testing with an FTDI USB to Serial converter cable.

It works fine when the cable is plugged up on startup but once I disconnect the cable from the computer, it will not register as a TTY serial port. I dont like having to restart the machine every time to get it connected.

I can see the device in the list when I run:

ioreg -p IOUSB

However it does not show up in my /dev/ folder.

What scan or tool do I need to use to get it connected as a TTY device?

Hmmm.

You can Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379

if no success— Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

It seems to me this is new behavior for macOS.

Scratch that idea. It's not new behavior. I tried two earlier macOS systems and they do the same thing.

It's unusual and unexpected: if you start from a cold boot with the device disconnected, it does not appear in /dev/ (obviously). If you connect the device, it spontaneously appears in /dev/ with no other action required, and everything works fine. If you disconnect the device, it disappears as you would expect. However, if you connect it again it will never appear until you reboot (or, perhaps log out. I didn't try that).

I know that doesn't help but at least it confirms it's not some new "security" nonsense, meaning you don't need to fight that losing battle. It's a peculiarity of macOS that appears to have existed for a long time, perhaps since its inception. If there is an answer you will most likely find it in Ask Different or Stack Exchange or perhaps in the Developer Forums.

bvch291 wrote:

Do you have this problem with prolific chipset devices?

Yes. Same exact behavior. I never noticed it because the device appears as expected when connecting it, but I never had any reason to disconnect it and subsequently reconnect it... exactly what you need to do.

I posted a question in the Apple Developer Forums: how does macOS populate /dev/ for connected devices and linked back to this one. Don't hold your breath waiting for an answer.

I posted a question in the Apple Developer Forums: how does macOS populate /dev/ for connected devices and linked back to this one. Don't hold your breath waiting for an answer.

No productive answers yet. I'm not holding my breath either, but I may pursue another line of research.

It shouldn't be necessary. Although I do not have any FTDI devices I use Prolific devices which you're probably aware are similar. Connecting it causes its previously installed kernel extension to change from "Not Loaded" to "Loaded". Disconnecting it unloads the Extension, reconnecting it loads again. No reboot necessary.

Did you install its driver?

I found an FTDI device and was able to duplicate what you described. If the device is connected at boot it works, but if you disconnect it the device disappears from /dev/. If you connect it again it will not reappear until after a reboot.

Unfortunately this is exactly what you describe: how to force macOS to check for connected devices and repopulate /dev/, and I don't have the answer.

What part of the system loads these devices?

Good question. This does not happen on Linux (for example). Connecting a device on a Linux system causes it to appear in /dev/. No reboot required. As to which part of the system loads it, I suspect there is another part of the system preventing it from appearing.

It seems to me this is new behavior for macOS. We can only speculate as to the cause, and I suspect it was in response to macOS's overbearing approach to system security. My only suggestion is to file Feedback and tell Apple to restore what I believe was prior behavior.

More than likely though, it's what I suspect: an overzealous approach to security, and if that's the reason you'll be arguing with a brick wall. I'd take your question to Ask Different or somewhere else where people delve into these things.

I still don't have an answer, but in the interest of continued research may I ask about the nature of your testing? Can you use a Prolific device? As far as your application goes it should work the same way, but as I wrote it still has the same problem in that the device will not appear in /dev/ when you need it to.

This driver on Prolific's website (enter "GUEST" on both Account and Password boxes) has an accompanying Installation Guide indicating support through macOS High Sierra. That Installation Guide works all the way through Step 4. It's Step 5 that doesn't work—the device should appear in /dev/ but it doesn't. That's a show-stopper.

If you're interested try that driver and report your results. I may try installing it on a HS system but I suspect Apple's recent Security Updates will prevent its installation. Let me know if you're interested, because I'm not really motivated to do it on my own if no one else cares.