R Series Adjacent DIO Pins Observing Voltage Spike Synchronized with Clock Input

Updated Mar 20, 2018

Reported In

Hardware

  • SHC68-68-RDIO

Software

  • LabVIEW FPGA Module

Issue Details

I am reading in a square wave on one of DIO pins on my R Series board (Figure 1). The adjacent DIO pins observe a voltage spike of at least 1 Volt (with or without the FPGA code running) that is synchronized with the negative edge of the square wave (Figure 2). How can I fix this issue?

Figure 1: Square Wave


Figure 2: Adjacent DIO Pin Reading Voltage Spike

Solution

When connecting to Connectors 1 and 2 on R Series devices, you should use the SHC68-68-RDIO to connect to the NI SCB-68, instead of the SHC68-68-RMIO. Table 1-3 of the NI R Series Multifunction RIO User Manual explains this.

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