LabVIEW
Controlling OBIS laser with Labview
@wjchen10 wrote:
Hi,
Has anyone successfully controlled a Coherent OBIS Laser using RS 232 or USB? I have followed the procedure here: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000x1qzCAA&l=en-US
But NI MAX will not communicate with the instrument. Thanks so much!
Please stop using this KnwoledgeBase article everyone!!!!!
It does NOT what everybody thinks it should do!!!
USB-TMC is a standard that is only implemented by a few measurement device manufacturers such as HP/Agilent/Keysight, Tektronix and similar. If a device implements that it can be pretty much controlled like a GPIB device. Your laser device is absolutely certainly NOT an USB-TMC device.
Leaves two other options:
It could be an USB-CDC device or use another standard USB-RS232 converter internally such as the Prolific or FTDI chip and then Windows will pick it up as serial device without you having to do anything.
It could also be another USB standard including a proprietary one. In that case VISA USB-RAW could have been a solution in the past if and only if:
- the manufacturer gives you an exact description of the USB low level protocol they use (In my software carrier so far this has happened exactly once and only because they wanted us to write a test application for their own hardware they were going to sell. And yes that document came with a heavy handed NDA that could have cost us a lot of money if we had spilled their secret protocol.)
- You are not afraid to do low level programming with bits and bytes and dealing with USB endpoints and what else.
Nowadays this USB-RAW driver model is almost useless because:
- Every commercial OS out there requires that drivers be signed by the developer/manufacturer with a valid certificate obtained from a globally recognized Certificate Authority
- The newest versions of OSes all require that it is not only signed by the developer/manufacturer but also submitted to the OS provider (Apple/Microsoft) for counter signing before the driver gets accepted to be loaded into the system. And every time you make even the tiniest modification to the driver you have to sign it again and resubmit it for counter signing.
So USB-RAW is never the solution anymore and hasn't really been in the past in most cases.
Back to your original problem:
- Coherent seems to have actually a LabVIEW driver for their Obis Laser devices: https://www.coherent.com/content/dam/coherent/site/en/resources/laser-measurement-and-control-help-c...
- They also have a C++ source code example to control explicitly their Obis LS/LX laser series through RS-485: https://repo.coherent.com/software/LX.zip
The first seems to simply make use of the standard VISA functions in LabVIEW to address a serial port. And it uses standard RS-232 but in a very bad way using the threaded Bytes at Serial port with a fixed delay before, even though the used protocol is actually using a termination character!
The second is supporting the Coherent CCB protocol over an RS-485 interface and could be fairly simply converted to a LabVIEW driver from a somewhat knowledgeable person. Which one of the two if any applies to your laser model is of course unclear to me. You will probably have to talk with Coherent technical support about that.
