Low-level switching in matrix mode with 1127?

[dcespin]

Hello,

I'm working on a specific switching application for testing many devices, and I have an SCXI chassis, two 1127 modules, and two 1331 terminal blocks. I control this hardware with an NI-MIO data card. Because of the nature of the application, we're using very low-level code to drive the switching hardware, referring to the register-level programming manual. I have been using the switching hardware in "independent" mode, but I can't get the routing of channels to outputs to be as flexible as I'd like it to be. The regular 1127 manual indicates that the module can be configured as a 4x8 matrix, but I'm not sure exactly how to configure it that way using only register-level commands. I'm also not quite sure whether that is the best mode to use the hardware in, as I'm looking for a way to route the channels to the ouputs as arbitrarily as possible.

If that's not very clear, then perhaps an example will help. There are 4 output channels and 32 input channels on the 1127, and I'd like to be able to route, say, channel 3 to OUT0, channel 6 to OUT1, channel 2 to OUT3, and channel 19 to OUT2. This may not actually be possible, but it would be good to have the routing capabilities be as flexible as possible to minimize the amount of rewiring on the terminal block in between batches of tests. I don't necessarily need a high available input count; routing flexibility is more important. Any suggestions on how best to achieve this would be highly appreciated.

Thanks!

[RossC]

Dcespin,

All of the routing/relay information for the SCXI-1127 can be found in the NI Switches Help file. This file is located in the Start menu at Start » Programs » National Instruments » NI-SWITCH » Documentation » NI Switches Help. Once you have the file open, go to Devices » NI SCXI 1127/1128 » Hardware Diagram. This shows a diagram of all the relays and how they are connected in the switch, as well as their software names. Using this, have all of the information needed to make any route possible with the 1127. If you want to operate in the standard 4x8 matrix mode, that is fine as well, though I would suggest you you the SCXI-1332 terminal block since it was made with the proper internal wiring for the 4x8 matrix. I hope this gives you a solid basis to build from, have a good day!

Sincerely,

Ross C
Applications Engineer

[charlesy]

Hello Dcespin,

From the hardware diagram that Ross describes, you see that you can't route multiplexer channels like CH3 to OUT0 and CH6 to OUT1 simultaneously because they share the COM0 path. The most flexible routing topology is a full matrix. In the 4x8 configuration, you can connect any combination of rows to columns. The matrix configuration is formed by shorting the 8 differential channels between banks, creating columns. The OUT+/- lines from each bank are now rows of the matrix. For example, tie CH0+/- to CH8+/- to CH16+/- to CH24+/- to make COL0+/-. The SCXI-1332 terminal block makes those connections for you, exposing only terminals for 4 differential rows and 8 differential columns. While the SCXI-1332 is more convenient, you can make the columns manually in the SCXI-1331.

I hope this is useful.

Charles