Experimental Physics and
Industrial Control System

Guy Jennings <[email protected]> · Thu, 18 Apr 2013 18:04:11 -0500

On Apr 18, 2013, at 5:12 PM, Andrew Johnson wrote:

Hi Mark,

On 2013-04-18 Mark Rivers wrote:

I don't have a serious need for this device, but there is an EPICS

user at

NIH, Andrew Gomella who needs to control 18 of the model 3006

devices,

which he is planning to do from a single Linux box.

Is this possible, even in kernel 3.8?

It should be possible even with your kernel version. The issue that

Guy

described is that the driver can only talk to one *type* of device

at once; so

as long as all 18 are the same model 3006 with the same product ID

he should

be fine.

Not quite what I meant - the ftdi_sio module can handle a mixture of

devices

from those device types it has compiled in, and ONE additional

vendor:product

combination passed as an option.

The other question is whether it provides a serial number attribute

that can

be used in a udev configuration file to ensure that the /dev/ttyUSB*

nodes

always map to the same physical devices. If there is no such

attribute then

unplugging 2 devices and plugging them back in could cause the

mapping to

change, which could be disastrous. Of course managing all 18 units

and

replacing them with spares still becomes a rather complicated chore.

If it doesn't provide a serial number he's in big trouble! I think

that the order

in which USB ports are scanned is deterministic, so as long as he

doesn't unplug

or replug a device the mapping might stay constant - but I wouldn't

like to rely

on it!

Guy

- Andrew
--
It is difficult to get a man to understand something, when his salary
depends upon his not understanding it. -- Upton Sinclair

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System