[Linux-ham] /dev ports for USB serial adapter

[Tadd Torborg]

fabulous.  Thanks.  
Tadd Torborg
tadd at mac.com



On Mar 1, 2014, at 9:39 PM, Bryan <n3txu at yahoo.com> wrote:

> A real-honest-to-goodness serial port will be /dev/ttySn (ttyS0, etc).
> 
> A USB serial adapter will show up as /dev/ttyUSBn.  (starting at 0 and going up depending on how many you have)  The model or brand make no difference that I've ever noticed.  99% of them are either PL2303 (Prolific) or FTDI.  If you have a choice, FTDI are the better option.
> 
> There is a generic module called usb-serial or something equally clever.  Unless you built your own kernel or did some other messing around, it should be there and load automatically.
> 
> There are modules for specific manufacturers (FTDI, prolific, etc). For your purposes, you shouldn't need to modify anything relating to how they are loaded.  When you plug in a USB to serial adapter for the first time, several modules will be loaded. Looking at my system, I see:
> 
> Module                  Size  Used by
> ftdi_sio               39699  0
> pl2303                 12309  0
> usbserial              30693  2 pl2303,ftdi_sio
> 
> 
> So, the generic module that is responsible for /dev/ttyUSBxx is usbserial.  I have both FTDI and Prolific serial converters, so there is a module for each manufacturer.  I didn't do anything more than just plug them in.
> 
> To verify which device file is created for your adapter.  Plug it in and type 'dmesg'.  you'll see output like this:
> 
> 
> [639950.114429] usb 6-4.3.2: new full-speed USB device number 10 using ehci-pci
> [639950.317740] usbcore: registered new interface driver ftdi_sio
> [639950.317792] usbserial: USB Serial support registered for FTDI USB Serial Device
> [639950.318212] ftdi_sio 6-4.3.2:1.0: FTDI USB Serial Device converter detected
> [639950.318288] usb 6-4.3.2: Detected FT232RL
> [639950.318295] usb 6-4.3.2: Number of endpoints 2
> [639950.318300] usb 6-4.3.2: Endpoint 1 MaxPacketSize 64
> [639950.318306] usb 6-4.3.2: Endpoint 2 MaxPacketSize 64
> [639950.318311] usb 6-4.3.2: Setting MaxPacketSize 64
> [639950.318813] usb 6-4.3.2: FTDI USB Serial Device converter now attached to ttyUSB3
> [639951.648565] usb 6-4.3.4: new full-speed USB device number 11 using ehci-pci
> [639951.758593] ftdi_sio 6-4.3.4:1.0: FTDI USB Serial Device converter detected
> [639951.758678] usb 6-4.3.4: Detected FT232RL
> [639951.758684] usb 6-4.3.4: Number of endpoints 2
> [639951.758690] usb 6-4.3.4: Endpoint 1 MaxPacketSize 64
> [639951.758696] usb 6-4.3.4: Endpoint 2 MaxPacketSize 64
> [639951.758701] usb 6-4.3.4: Setting MaxPacketSize 64
> [639951.759084] usb 6-4.3.4: FTDI USB Serial Device converter now attached to ttyUSB4
> 
> 
> For me, those last two adapters are /dev/ttyUSB3 and /dev/ttyUSB4. You can see a bit about what happend when the adapter was plugged in.  First, usbcore noticed a new thing.  Then it said that's a usbserial adapter and saw it is an FTDI adapter and loaded ftdi_sio.  And you can also see how far along the USB bus it is (device number 10 and device number 11).  By and large, the only thing you care about here is the ttyUSBx
> 
> Hope that helps!
> 
> -- Bryan
> 
> 
> 
> _______________________________________________
> Linux-ham mailing list
> Linux-ham at trilug.org
> http://www.trilug.org/mailman/listinfo/linux-ham