[Libusb-devel] USB error reading USB config strings on Linux

[Douglas S. B. <db...@br...>]

libusb-developers,

I'm just setting out to reverse engineer a robot that has a proprietary 
USB interface. The first goal is to figure out how to send it commands 
to make it move (it has two stepper motors, each controlling a wheel).

I'm new to USB programming, and after looking at many interfaces, I'm 
trying libusb.

Trying the tests/testlibusb program that comes with libusb-0.1.7, I'm 
able to see the robot USB data somewhat. But I get errors whenever I try 
to read a string (manufacturer, vendor, or serial number).

I've traced it down to the line:

ret = ioctl(dev->fd, IOCTL_USB_CONTROL, &ctrl);

in linux.c in the function usb_control_msg() which returns -1 on reading 
the strings (other functions seem to work).

I'm running RedHat 9.0, kernel 2.4.20-28.9smp.

Some questions:

1. Is this the right project for the job (being that I'm not that 
experienced with USB programming)? Should I consider using usbserial? Or 
something else?

2. If this is the right project, can someone help with the above error?

3. Where do I go from here?

Additional data:

I can see the strings if I:

$ cat /proc/bus/usb/devices

T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#=  3 Spd=12  MxCh= 0
D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=deee ProdID=0300 Rev= 2.00
S:  Manufacturer=Evolution Robot
S:  Product=ER1 Control Module v1.0
S:  SerialNumber=ER1U1F73
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
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


Any pointers would be much appreciated!

-Doug

-- 
Douglas S. Blank,         Assistant Professor
db...@br...,            (610)526-6501
Bryn Mawr College,   Computer Science Program
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