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Invalid SDI-12 parsing from WXT using CR1000

pokeeffe Aug 18, 2022 09:39 PM

I keep finding invalid data in 1-minute statistics from a WXT510 and determined the cause is data occassionally being stored into the wrong destination. Screenshot linked below - note the Wind Speed column contains Pressure, Wind Direction contains Wind Speed, and Rain_amt contains Heater Voltage (not shown in table). 


I'm using the Continuous Measurement (aR) command documented in the WXT510 User's Guide (rev 2006) to obtain a combined data message for all enabled sensor messages every 5 seconds (in a SlowSequence). The WXT510 is configured to poll sensors every 5 seconds and to include 9 data values in the composite message (which is less than the maximum of 15 allowed per response message). The variables in my destination array are carefully arranged to match up with the order of variables in the data messages from the WXT510. So it's not clear why certain data messages get incorrectly parsed. The vast majority of received data messages get handled correctly but if a single message is broken, then the aggregate data is invalid. 

Should I switch to CRC validated messages? The relevant CRBasic help article does include RC! as a valid command whereas R! is apparently not. 

Or should I use R0! instead? It's listed as a valid command for `SDI12Recorder()`, even though the WXT510 User's Guide only mentions it in the context of ASCII mode (the section on SDI-12 communications only mentions R! not R0!). 

First I'm going to try the CRC validation. That should hopefully be enough to prevent the logger from parsing partial data messages. Thank you for reading my confused rambling. I'll post a reply if/when I figure it out. (Full disclosure the CR1000 was running OS.Std.32.02 so I'll update to 32.05 in addition to editing the program.) 

pokeeffe Aug 20, 2022 01:05 AM

OK.. two things of note I guess:

1) If you specify R! or RC! for the SDI-12 command, the datalogger automatically issues a corresponding R0! or RC0! instead.

2) Yes, CRC validated messages seem to be the (obviously) better choice. I've only evaluated for a half-day but I no longer see mix-ups in the SDI-12 data parsing.

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