Usb-serial adaptor


#1

I have a new macbook air … macos 10.13.6 …
trying to use USB Serial adaptor
installed the prolific driver … got past gatekeeper …
installation said it was successful …
device appears under system report of system information …
product id 0x2303
version 4.00

I have used this converter and associated driver with another (older) macbook running macos 10.13.6 (and previous) for several years … works fine on that computer …

ioreg -c IOSerialBSDClient | grep usb

shows nothing …
ls -l of /dev/cu.usbserial shows nothing …

suggestions?

Terry


#2

Hi Terry,

Thanks for reaching out to us, I am sorry this is not working as expected.

We can start by verifying the Prolific USB to Serial kernel extension ( KEXT ) is loaded in the system. Please open a terminal ( Finder > Go > Utilities > Terminal ) and enter the following command:
kextstat | grep -i “prolific”
This should return a line of text containing “com.prolific.driver.PL2303” if the kernel extension is loaded, if the extension is not loaded this will be blank.

To manually load the Prolific kernel extension we can use the following command:
kextload /Library/Extensions/ProlificUsbSerial.kext

If successful, rerunning the kextstat command above should now work, and the /dev/tty.usbserial and /dev/cu.usbserial should now exist.

Please let me know if this helps, or let me know if there are any errors produced manually loading the kernel extension and we can go from there.

Thank you,

Pat.


#3

Pat … thanks for the quick reply …
output from your suggestions below … (RR is shell prompt)
kextstat piped thru grep produced nothing …
kextload indicates some type of system policy problem …
not sure how I correct the policy problem …

Terry

RRkextstat | grep -i “prolific”

RRsu

Password:

sh-3.2# kextload /Library/Extensions/ProlificUsbSerial.kext

/Library/Extensions/ProlificUsbSerial.kext failed to load - (libkern/kext) system policy prevents loading; check the system/kernel logs for errors or try kextutil(8).

sh-3.2# kextutil /Library/Extensions/ProlificUsbSerial.kext

Kext rejected due to system policy: <OSKext 0x7ff00fc1c580 [0x7fff8c3a8b30]> { URL = “file:///Library/StagedExtensions/Library/Extensions/ProlificUsbSerial.kext/”, ID = “com.prolific.driver.PL2303” }

Kext rejected due to system policy: <OSKext 0x7ff00fc1c580 [0x7fff8c3a8b30]> { URL = “file:///Library/StagedExtensions/Library/Extensions/ProlificUsbSerial.kext/”, ID = “com.prolific.driver.PL2303” }

Diagnostics for /Library/Extensions/ProlificUsbSerial.kext:

Warnings:

Dependency lacks appropriate value for OSBundleRequired and may not be available during early boot:

com.apple.iokit.IOSerialFamily - Safe Boot


#4

Pat …I found a panel under System Preferences -> Security and Privacy -> General …
I tried to allow system software from Prolific to be loaded … but I don’t think it worked …
perhaps I have to reboot?

Terry


#5

Hi Terry,

Thanks for the additional details. It sounds like the system is blocking the KEXT, after allowing Prolific in the Security and Privacy tab I think it requires a reboot to start the load the KEXT, you may be able to load the file manually, but I recommend the reboot.

Please let me know if this works after the restart.

Thank you,

Pat.


#6

Pat … unfortunately the load didn’t work after a reboot …
after unlocking the pane, I’ve hit the allow button multiple times
then locked it to save changes … and tried the kextload command several times, as in:

sh-3.2# kextload /Library/Extensions/ProlificUsbSerial.kext

/Library/Extensions/ProlificUsbSerial.kext failed to load - (libkern/kext) system policy prevents loading; check the system/kernel logs for errors or try kextutil(8).

sh-3.2#

Terry


#7

Hi Terry,

Thank you for giving that a try. To clarify, doe the “Security & Privacy > General” panel still show the option to allow the Prolific software or did this go away after selecting to Allow?

Please also let me know if the setting to “Allow apps downloaded from:” is set to “App Store and identified developers”, this is located on the “Security & Privacy > General” panel.

While I have not been able to reproduce a similar error I have had other customer’s report similar issues where macOS would not allow the drivers to start even after reinstalling the drivers multiple times, updating the system and going through the steps to allow Prolific software. Disabling System Integrity Protection and reinstalling the driver using the instructions in the zip file, then verifying the serial adapter is functional, then re-enabling System Integrity Protection then allowed the software to load correctly at boot. If you would like to give this a try let me know and I can provide some additional instructions, please note, disabling System Integrity Protection may leave the system vulnerable to malicious software until System Integrity Protection is re-enabled.

Thank you,

Pat


#8

Pat … I’ll try this … but it will have to wait until Friday …
thanks for your help so far …
have a happy Thanksgiving!

Terry


#9

Hi Terry,

Thank you for the update, we will be closed on Thursday, and I will be able to help answer additional questions on Friday if you run into any issues.

Thank you, and happy Thanksgiving to you too!

Pat


#10

Pat … the panel no longer shows the option of allowing Prolific …
it has gone away …

the setting is set to the App store and identified developers …

I can try disabling SIP … I found directions on the web on how to do it …
I assume I uninstall the Prolific software, disable SIP, re-install the driver,
test driver, then re-enabler SIP … is that correct?

Terry


#11

Hi Terry,

Thanks for double checking this! For disabling SIP, I do recommend removing the Prolific drivers first, instructions are provided in the PDF file in the driver zip file ( near the end of the file ) which includes deleting the driver files from the terminal. After the drivers are removed, please restart the system before disabling SIP, and with SIP disabled reinstall the driver package and test the USB serial adapter before re-enabling SIP to verify it is working with the system.

Please let me know if this helps to get the driver functional on the system.

Thank you,

Pat


#12

Pat … the system seems to work when SIP is disabled …
but when I (re)enable it, it stops working …
I tried this twice to confirm (a lot of re-boots!)
driver accessible when SIP disabled, but not when enabled …

I am now in disabled mode and I see in Security & Privacy>General that Prolific software was blocked from loading … I’m going to hit the allow button …
I hit it and the message stays there (btw, the appstore and identified developers is selected)

fyi, the device my software accesses is /dev/cu.usbserial

Terry


#13

Hi Terry,

Thank you for giving that a try, unfortunately we have not seen this behavior before. Normally after re-enabling SIP the driver will load normally.

Can I have you delete the current driver zip files and download the driver from our website here ( https://plugable.com/drivers/prolific ) then re-install the driver to make sure there is no corruption in the downloaded file. If this fails to correctly install on the system it may indicate a problem with the SIP’s ability to allow 3rd party software. If you have not already updated to MacOS 10.14 Mojave, this update may reset SIP and allow the software to allow the Prolific USB-to-Serial driver.

Please let me know if a fresh download of the driver helps,

Pat


#14

Pat … I went to Mojave and finally got it to work …
If I have any more problems I’ll be in touch …
thanks for all your help …

Terry


#15

Hi Terry,

Glad to hear it is working under Mojave! I am sorry it took so much effort to get the drivers loaded.

Thank you for the update, I will be marking this topic as closed. If you have any additional questions please feel free to open a new topic or send us an email at support@plugable.com.

Have a great day!

Pat


#16