Over the past two days, I am doing some reading on how to get data over USB from an external device which has no device driver installed. I have to read data from a WT500 Yokogawa Power Meter (basically I want to read just one of the parameter that the meter shows, just the power values) over USB. I am aware that a device driver for WT500 is available, but it has some dependencies and I do not want to install a software or change anything majorly in our node to cater to that.
I have found that libusb could be used to perform what I would want, and I have a C program that sniffs the USB device and returns some information. I have looked into usb-robot as well, which also uses libusb. The server node that I am probing has OpenSUSE Linux kernel 2.6.30. I have usbfs mounted.
Question:
- I am expecting that using libusb, I would be able to get data dumps from the power meter whenever I request, via usb device. Can I request the meter something like - send 25k of data, and then upon parsing it, I get the parameter value that I am looking for? Considering that I have zero knowledge about the device, can I get some meaningful values out of it? An example code would help.
-- There are some standard messages like ?IDN with which a USBTMC device could be queried. However, specific queries need to be sent to a meter (the syntax should be there in the technical doc/manual/communication interface) if one needs to get whatever is showing up on screen.
- I guess there are no easier ways of doing what I want - like just reading a file using something like fread ??
--
Yes, almost. If USBTMC module is installed (the default one in our kernel did not work, detailed explanation of installing and querying a device is here - http://code.google.com/p/scte/wiki/USBTMC), then one just needs to send some queries and read the response via cat or something from the specific files under /dev.
From the meter technical document, I see that the driver communication interface that is described is Windows specific, so I reckon I might need to do some reverse engineering.
-- Yes, but only a tiny bit or may be not at all.
Thank you.
EDIT: After a bit of googling I think I have the answers, I have added them next to the questions I asked.
