Inconsistent ProXR Lite Relay Operation when Polling Inputs


We’re testing the NCD Relay Controller 4-Channel General Purpose SPDT + 8 Channel ADC ProXR Lite.

We’re running a parking application where we are getting inputs from the induction loops and then taking different action based on the condition of Loop-1, Loop-2, etc. Based on the inputs, we trigger UHF RFID reads for 750-msec and then take action depending on whether the tag is authorized…

We have code that is polling the state of the inputs 20-times/per second (50-msec) via:

170 2 254 166 80

It consistently returns 8-bytes of data as expected

170 9 255 255 255 255 255 255 255 255 170

Upon observing an input, we issue a command to operate a relay such as:

170 3 254 108 1 24

And may wait 1-sec and turning off the relay via:

170 3 254 100 1 16

In every case the relay commands are sent, we receive the acknowledgement of:

170 1 85 0

However, the relay may or may not really operate. Seems intermittent at best. Is it possible that there is contention between a 50msec poll and the relay commands?

Any thoughts on how we might poll at this rate with more consistent relay control/behavior? Thanks in advance…

You will need to stop polling before changing relay states, you cannot do both at the same time as the cpu can only execute one command at a time. Please test all operations with Base Station ( as all routines properly handle communications and response from commands.