7329178 Brandon Brice

[Climatic_Testing]

Brandon:

Again:   

Our Ethernet connetion between the 9188 and the PC is dedicated.  The cDAC communications is the traffic.   We have eliminated the switch and are the 9188 is connected directly to the PC via a single cable.  The only thing running on the PC is the application.

If the application is started before the active light flashes for the first time (about 3 to 5 Min) we never get data.  We eventually read the chassis information, but not module information, and we cannot read the analog data.  This condition remains until we restart the application after the active light flashes on the 9188.

Typically, the I/O devices we work with, including the ones from NI do not require a system startup breath holding or cause a loss of data.  And if any device is out of communiction, recovery is automatic, without reboot or user action.  We previously used the 9178 with favorable results.  The expectation was that the 9188 would give similar performance as the 9178 with the connection protocol being transparent to the application.  There is no intent to connect this computer to the Internet and our instructions have a caviate that prohibits such an Internet connection, warning that such a configuration voids any performance requirements.

Our customer is confused as to why the 9188 data is unreliable.  From his perspective the unit is malfunctioning.  They wonder why we are using the 9188 for their application which depends on reliable and accutate readings for their testing.

I gather from your response that our descrition of the operation is normal and expected for the 9188.  And I also understand the NI support facility does not have the resources to replicate our configuration of Windows 7 accessing a 9188.

Your best recommendation is to minimze the Ethernet traffic and simply wait until the 9188 is available before starting the application.  We have already eliminated the switch and the 9188 owns the Ethernet.  

Telling our customer to wait until the 9188 is ready is a huge problem because the unit is in a sealed cabinet that is not close to the control console the operator uses.  So the active indicator is not visible to the user.

Please consider the one or more of the following that would allow the customer to be ignorant of the doings of the 9188:

1) Establish proven recommended settings/procedures/priorities for Windows 7 startup to minimize the delay in the 9188 active state we are experiencing.  Three minutes is to long.

2) A programatic way that we can let the user start the application that we can detect that we need to wait for the 9188 to establish itself.

3) A function or functionality that allows a hung up 9188 to recover in a startup situation without restarting the application.  If the application is started too soon, eventually, when the 9188 is active, we can automatically restore data collection.

It is important the the 9188 functionality be embedded in the application and tranparent to the user.

Hopefully there is a path or one will surface that will be satisfactory to our customers.

Thanks,

Aram

[Corby_B]

Hello Aram,

Thanks for post on the DAQ forums. I have some items and advice that can ease concerns about your customer application.

1. How long it takes for the 9188 to be recognized by the PC.

I must first say that your network topology and set up is a huge factor in how long this will take. For instance, I notice that you are connected directly to the PC instead of going through a router. This is a big advantage for the 9188 to be able to connect directly to a PC but there are some things to consider:

A. By not using a router or DHCP server this means that the 9188 and Windows host machine must negotiate for their IP address settings in the link local IP address domain. This can literally take from 1 -5 minutes depending on the windows machine. Windows will let you know when it is finished resoling network settings by the icon in the lower left corner of the screen or taskbar

B. Using a router that can assign DHCP IP addresses may be the best method if speed is a concern. This can also be referred to as using a network infrastructure. By letting dedicated hardware assign out IP addresses this can give some time back to your PC and Network cDAQ. Some examples are:

Linksys standard router

MOXA industrial router if temperaure and environment are a concern. 

C. Using a switch could result in similar time delays as point A if it cannot assign out IP addresses automatically. 

2.How to know when the 9188 is ready and network settings have been resolved.

Instead of just waiting for the network, computer and cDAQ to establish connections, there is a programmatic way to determine if your chassis is available or not. Using the DAQmx API you can call to see if the device is reserved for your system or not and do a self test. If you get error -201250 then the device is not ready to be used. This error will clear when you are able to successfully communicate with the cDAQ chassis. I would recommend using the DAQmx reserve network device.vi as it sounds like there are computer restarts involved with your application. See the code below for an example of this.

There are some inherent latencies in Ethernet network configurations that can cause the cDAQ to not be recognized as fast as a USB cDAQ for instance. I hope the points above have helped, let me know if there is anything else I can explain further. You are correct that while the DAQmx API was intended to be transparent when program, there are still some things to consider when using a networked device.

3. Network Connection Lost

We of course hope this does not happen. If you lose a network connection you will get an error in the DAQmx API when this happens. The 9188 will of course try to re-establish a connection with its host or network. On the host PC simply clear the current task that is running, clear the error and try to create a new DAQmx task. This is the best way to try and re establish communication with the chassis. Error handling is very important when it comes to network DAQ devices to know when to handle these events. See an example of this below:

https://decibel.ni.com/content/docs/DOC-11073 

Have a great day Aram and please let us know if there is anything else we can do. 

On a side note, I have followed up with our support department to make sure they have the capabilities to replicate systems like this. 

Corby

Network cDAQ R & D Product Support Engineer

[Corby_B]

 You could also make your network static. This will rule out any network negotiation with a host PC or DHCP server because the network paths are static. Going directly to a host PC would look something like this:

Host PC - 192.168.1.10

255.255.255.0

cDAQ-9188 -192.168.1.11

255.255.255.0

Make sure and use private network  configurations.

Corby

Network cDAQ R & D Product Support Engineer