DAQmx Tool for Lost Ethernet Connection

[Bryan24]

While working a project utilizing NI cDAQ-9184 Chassis, I doscovered the following problems.

1. There is an undocumented "heartbeat" protocol between the remote chassis and the host computer.

2. There is no documentation that explains how this "heartbeat" works.

3. There is no specification for how long the heartbeat is lost before the cDAQ Chassis goes into the "lost heartbeat" mode.

4. There is no way to poll the cDAQ Chassis to discover if it lost the "heartbeat" since the last time you accessed the Chassis. This is very important if you have a long time between data reads.

5. Once the "heartbeat" has been lost, the chassis essentially unlinks the 'module side' from the 'ethernet side'. There is no way to poll the Chassis to find out if it is in this state or not.

6. If you give the chassis a 'Self Test.vi' command, a Chassis will normally respond in only a couple of hundred milliseconds. If you give the same command to a Chassis that has lost the heartbeat, it will "re-link" the Module side of the chassis with the Ethernet side of the Chassis. However, this takes several seconds, which is undocumented, and the "Self Test.vi" returns no information telling you that a "Re-Link" occurred.

7. We have no way of knowing if the Chassis experienced a power loss.

8. I received no definitive answer if the modules in the cDAQ-9184 Chassis retain their configuration if power is lost to the Chassis.

Here is the main problem. If you set up the cDAQ-9184 for an acquisition, and experience a "Lost Heartbeat", the Chassis returns an ERROR when a read command is executed. That error gives you insufficient information to know what has happened with the Chassis. At that point, you are reduced to reconfiguring the cDAQ Chassis.

Suggested new software tools:

A. A "new PING" tool in the Functions>Measurement I/O>DAQmx-Data Acquisition>Advanced>System Setup. This would allow a user to "ping" the IP address of a remote chassis to insure the physical connection is established and that power is ON at the remote Chassis.

B. Anew tool in the Functions>Measurement I/O>DAQmx-Data Acquisition>Advanced>System Setup, most likely a modication to the Device Node. We need the ability to ask the Chassis if it has lost the "heartbeat".

C(a). A new tool that would instruct the Chassis to "Re-Link" if a loss of heartbeat occurred.

C(b). A modification to the Measurement I/O>DAQmx-Data Acquisition>Device Configuration>"Self Test.vi" that would return a response if the Chassis "re-linked" the Module side with the Ethernet side. 

D. A register that is set "High" upon power-up. The user would be able to set the Register "Low". At any time, the user could poll the Chassis for a Loss of Power occurrance.

Bryan Alexander

MSFC-NASA

[Darren]

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