On 06/09/2016 10:55 AM, Michael Eder wrote:
I have a question related to how one can distinguish between the
devices when there are multiples of the same FTDI devices plugged into
a USB hub?
I suspect the answer is to program the FTDI devices with a unique name
in its EEPROM, but is there a way short of that how I can identify
what device is plugged in where?
Simple example. I have two temperature I2C devices that have the same
fixed I2C address. I need to use two FTDI devices to talk to each of
these. One I2C device is in the front of my boat the other in the
back. If I always plugged the front FTDI USB device in the same port
on the USB hub and the back one also into a particular port could I
that way know which device is which and, if so, how can I identify the
usb port with the libftdi? Would this mechanism work even if I
plugged and unplugged the devices in at different times, but always to
their assigned port.
Any suggestions how to best do this greatly appreciated.
Is this a Linux/Unix system? If so you should be able to use udev to do
this for you with a little bit of data collection.
The FTDI devices that I've used have a serial number stored in EEPROM
that also shows up in the USB descriptors.
Connect one device at a time and see what device it creates in /dev
Use "udevadm info --name=/dev/SOME_DEVICE --attribute-walk" to see the
udev info for your devices which should include
something like this:
ATTRS{serial}=="FTV6IFNT"
With this information, you can write a udev rule to create a symbolic
link in /dev that makes them easily identifiable.
Here's an example that use for a system that has an FT230 and a UB232R.
SUBSYSTEM=="tty",ATTRS{idVendor}=="0403",ATTRS{idProduct}=="6001",ATTRS{product}=="UB232R",GROUP="plugdev",SYMLINK+="ttyUSB.lcd"
You could try something like this after updating the idProduct, serial,
and symlink names as appropriate.
/etc/udev/rules.d/99-i2c-temp-sensors
SUBSYSTEM=="usb",ATTRS{idVendor}=="0403",ATTRS{idProduct}=="6001",ATTRS{serial}=="FTV6IFNA",GROUP="plugdev",SYMLINK+="i2c.front.1"
SUBSYSTEM=="usb",ATTRS{idVendor}=="0403",ATTRS{idProduct}=="6001",ATTRS{serial}=="FTV6IFNB",GROUP="plugdev",SYMLINK+="i2c.front.2"
SUBSYSTEM=="usb",ATTRS{idVendor}=="0403",ATTRS{idProduct}=="6001",ATTRS{serial}=="FTV6IFNC",GROUP="plugdev",SYMLINK+="i2c.back.1"
Setting the group to plugdev is a convenient way to give your user
access without requiring root/sudo. You may need to add your user to the
group.
Ryan
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Distant Focus Corporation
4114B Fieldstone Rd
Champaign, IL 61822
http://jupiter.distantfocus.com/projects/
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