It’s not that I want to attach a USB-to-Serial dongle to my PC and
talk to the BeagleBoard (BB). I want to plug the dongle into the BB
(USB side) and write some code to talk to other junk (like my LCD
display, GPS module, etc.). I’ll write my own “C” code to talk to
these.
I’m brand new at doing this Linux stuff. I loaded Angstrom (kernel
2.6.32) onto the BB and I have it running. I can access the BB
through an LCD monitor (on the DVI port), USB keyboard, and USB mouse
(I have a self powered USB hub). I also have the system console
working out of the RS232 port of the BB. From a console in the
Angstrom GUI, I can output to the RS232 console by doing this from the
command line:
# echo “Hi Curt” > /dev/ttyS2
I have three different USB-to-Serial adaptors and they all seem to do
the same thing (not work). I will limit this description to the
“USB-2920” from Cables Unlimited. It looks like this is using the
FTDI chipset which seems popular.
The dongle is plugged in at startup to the “HS USB Host Port” on the
BB via the self powered hub. Using the “dmesg” command, I can get the
messages associated with the USB/Serial dongle:
<snip on>
[ 22.197753] usb 1-2.4: new full speed USB device using ehci-omap
and address 5
[ 22.336853] usb 1-2.4: New USB device found, idVendor=0403,
idProduct=6001
[ 22.344268] usb 1-2.4: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[ 22.352447] usb 1-2.4: Product: FT232R USB UART
[ 22.357513] usb 1-2.4: Manufacturer: FTDI
[ 22.362060] usb 1-2.4: SerialNumber: A600dqpX
<snip off>
Using the “cat /proc/bus/usb/devices” command, I get the following
messages associated with the dongle:
<snip on>
T: Bus=01 Lev=02 Prnt=02 Port=03 Cnt=03 Dev#= 5 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
P: Vendor=0403 ProdID=6001 Rev= 6.00
S: Manufacturer=FTDI
S: Product=FT232R USB UART
S: SerialNumber=A600dqpX
C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr= 90mA
I:* If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
E: Ad=81(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
<snip off
I don’t see any new devices in the “/dev/” directory that might be
associated with the dongle. From a console with user privileges, I
get the following result:
<snip on>
curt@beagleboard:~$ echo "Hi Curt" > /dev/ttyUSB0
-sh: can't create /dev/ttyUSB0: Permission denied
<snip off>
If I get to a root shell by doing “su –“, then the command doesn’t
report any errors:
<snip on>
root@beagleboard:~# echo "Hi Curt" > /dev/ttyUSB0
root@beagleboard:~#
<snip off>
I still don’t see any RS232 text out of the dongle with the above
command. But now the “/dev/ttyUSB0” device shows up in the directory.
So any ideas of how I can get a USB-to-Serial adapter to work when the
USB is plugged into the BeagleBoard?
Curt