Monitoring RS485

Good Day,

I'm working on troubleshooting a weather ceilometer that uses mainly RS485, but has the ability to use RS232. I'm using the IO Ninja Hardware Tap. When wiring the ceilometer for RS485, we so no data coming across, just DTR On DTR Off signals and .. response back.

When we wire it for RS232 we see a lot of Line error detected framing error. Although we do see the data expected, but it appears to be broken by Line error detected: Framing errors. I have attached a pic.

I'm assuming there is something wrong with the DAC for this ceilometer, but I just want to confirm that I am using your software and hardware properly.

Here is a picture I took of the data. According to the ceilometer manual the data should look like TR1 AAAAAA HHHHH TTTT HHHHH TTTT HHHHH TTTT HHHHH TTTT VVVV RRRRR
which is what the picture attached sort of shows, but with those Line error detected between the packets
I did however see
TR1 AAAAAA HHHHH TTTT HHHHH TTTT HHHHH TTTT HHHHH TTTT VVVV RRRRR
data come through the data logger at some point in testing, but I can never re-create that config.

Any help is greatly appreciated.

Thanks

Here is a link to the sensor manual if that helps

https://www.allweatherinc.com/wp-content/uploads/8339-F-001-1.pdf

Page 17 talks about data communication specifically.

Hello Kenny,

RS485 should work; please check your wiring. A common misconception with wiring for RS485 is discussed in this topic: https://ioninja.com/forum/topic/14/rs485-modbus-rtu-comms-snooping

Re FRAMING errors -- these may be symptoms of wrong serial parameters (baud/data/parity/stop).

Since you see some sensible chars and not just garbage, the baud rate is most likely correct (still, double-check it, please). If I had to take a guess, I would blame the parity bit (either the actual link is using it, but Serial Tap doesn't, or vice versa). In any case, pay attention to all the serial parameters and make sure they are the same on both the Serial Tap and the actual link that you are snooping.