Connecting to a device console using screen shows no output
I am trying to access a network device console from my mac using a Prolific Technology USB-serial adapter to the device's console. After installing the relevant driver, the adapter is correctly shown:
$ ioreg -p IOUSB -l
...
+-o USB-Serial Controller@14200000 <class AppleUSBDevice, id 0x10000034a, registered, matched, active, busy 0 (101 ms), retain 11>
| {
| "sessionID" = 1402970206
| ...
| "bDeviceSubClass" = 0
| "bcdUSB" = 272
| "USB Product Name" = "USB-Serial Controller"
| "PortNum" = 2
| "non-removable" = "no"
| "IOCFPlugInTypes" = {"9dc7b780-9ec0-11d4-a54f-000a27052861"="IOUSBFamily.kext/Contents/PlugIns/IOUSBLib.bundle"}
| "bDeviceProtocol" = 0
| "IOUserClientClass" = "IOUSBDeviceUserClientV2"
| "IOPowerManagement" = {"DevicePowerState"=0,"CurrentPowerState"=3,"CapabilityFlags"=65536,"MaxPowerState"=4,"DriverPowerState"=3$
| "kUSBCurrentConfiguration" = 1
| "Device Speed" = 1
| "USB Vendor Name" = "Prolific Technology Inc."
| "idVendor" = 1659
| "IOGeneralInterest" = "IOCommand is not serializable"
| "IOClassNameOverride" = "IOUSBDevice"
| }
To access the console, I started screen from Terminal as per below:
$ screen /dev/tty.usbserial 9600
When I power on the connected network device, I can see the cursor bounces around randomly as if responding to the device console output, however no characters appear on Terminal at all. I know the USB-serial adapter is working fine, as using it on a Windows machine, I am able to access the same network device console without any issue. Any idea how to address this?
Thank you.
Since I couldn't get this working on my mac after multiple days, I decided to try my luck with a Debian 9 VM running in VMware Fusion within this mac. As soon as I made the device available within Debian VM, it was automatically detected and an associated tty* device was created:
# lsusb
Bus 002 Device 002: ID 0e0f:000b VMware, Inc.
...
Bus 001 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
...
$ ll /dev/ttyU*
crw-rw---- 1 root dialout 188, 0 Dec 29 14:30 /dev/ttyUSB0
Unlike /dev/tty.usbserial within macOS which was open for group others, device /dev/ttyUSB0 wasn't. So, I started screen with sudo:
$ sudo screen /dev/ttyUSB0 9600
And voila, it worked, as per the following screenshot!
I guess this is still a workaround. Checking the screen status (Ctrl-a + Ctrl-i (macos), Ctrl-a + i (Linux)), the latter had CD in brackets, implying signal CD was in effect:
That is the only significant difference that I could spot. Hope this helps others.