After much testing, it seems that usbserial has problems connecting usb
serial converters to /dev.
The system being tested is three Beagleboard xM rev C boards with the
Angstrom version sent with the board from Digikey as well as a recent
Angstrom build using Narcissus. Connected to the board is a USB 2.0 hub
with a USB mouse and USB keyboard which work perfectly.
Three USB serial converter cables were tested with the above boards and
OSes. Each cable had a serial converter chip from a different
manufacturer. The manufacturers were Prolific (the most common), FTDI, and
MOSCHIP. Prolific never worked, not even partially. FTDI and MOSCHIP
almost worked.
The tests went as follows:
The beagleboards were booted from power up after a clean shutdown.
Power was supplied from a 5V wall adapter.
Ethernet was supplied from a DSL connection
HDMI video was used (the console ttyS0 port was not used)
A USB mouse and keyboard was connected through a USB 2.0 hub
At this point, the beagle board xM works fine. No problems.
lsusb was executed to see the state of the USB devices connected to the
system, as shown below.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 002: ID 0424:9514 Standard Microsystems Corp.
Bus 002 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 002 Device 004: ID 0409:005a NEC Corp. HighSpeed Hub
Bus 002 Device 005: ID 0b39:0001 Omnidirectional Control Technology, Inc.
Next, the FTDI serial cable is connected.
ls /dev is executed to see if /dev/ttyUSB0 appears. It does not.
lsusb is executed to see if the FTDI cable shows up. It does show up as
shown below.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 002: ID 0424:9514 Standard Microsystems Corp.
Bus 002 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 002 Device 004: ID 0409:005a NEC Corp. HighSpeed Hub
Bus 002 Device 005: ID 0b39:0001 Omnidirectional Control Technology, Inc.
Bus 002 Device 006: ID 0403:6001 Future Technology Devices International,
Ltd FT232 USB-Serial (UART) IC
modprobe usbserial vendor=0x0403 product=0x6001 is executed.
ls /dev is executed to see if /dev/ttyUSB0 shows up. It does show up.
0 crw-rw---- 1 root dialout 188, 0 Sep 12 21:40 /dev/ttyUSB0
next, picocom is started with the following line
picocom --b 115200 --f n --p n --d 8 /dev/ttyUSB0
picocom reports :
picocom v1.4
port is : /dev/ttyUSB0
flowcontrol : none
baudrate is : 115200
parity is : none
databits are : 8
escape is : C-a
noinit is : no
noreset is : no
send_cmd is : ascii_xfr -s -v -l10
receive_cmd is : rz -vv
Terminal ready
With an oscilloscope connected to the serial output line, typing on the
keyboard causes characters to be sent, but at 3,000,000 bps, not 115,200
bps. Also, the screen fills with a repeated character continuously as if it
were receiving something. The scope shows that no signal is being sent, the
RS232 input line is at a high voltage. (On the FTDI part, I have a direct
connection to the low voltage high speed output that connects to the RS232
level shifter.)
This test was redone using the minicom program. The results were the same.
This test was performed on the other beagle boards with both the Digikey OS
version and the latest Narcissus version. The results are the same.
The MOSCHIP serial cable was very similar, except that it did not have the
endless false characters.
I'm working on a product that needs serial comm. I'm hoping that this issue
can be fixed or worked around.
--
Best Regards,
Marcus Escobosa
marcusescob...@gmail.com
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