I am having an issue with random ghost DM1 alarms on the display when I boot up connected to my system. I have looked at teh J1939 bus and my system is sending the DM1 PGN as 2 bytes with both bytes as 0s. Those are the lamp status bytes. It is sending no SPN information. It looks like the PV750 is trying to assume values of 1s for the bytes past byte 2 (spn bytes) up to 8 bytes, which are being intrerpreted as alarms by the PV750. The thing is, that it is not simply assuming that all bytes for the SPN are 255, as that would only interpret as 1 SPN, which I could drop in the configuration. It appears to be randomly assuming the bits.

Anyway, the alarms are always poping up as green and and going away as soon as they are acknowledged, but it happens (and triggers my audible alarm) every time the whole system is powered up for about 15 seconds. Sometimes I only get 2 alarms, sometimes it is 15. I have monitored the J1939 bus and there are no real DM1 alarms on the bus, only the 2 bytes of 0s.

For the time being, I keep adding the ones I see to my configuration and dropping them, but I continue to get ones at random.

I don't thing the system should assume bits when it recieves DM1 messages (as it standard with measurement and status PGNs), as all bits set to 1s are a valid piece of data in a DM1 message.

I think I may have figured out the randomness of the alarms. It appears that the DM1 application is ignoring the DLC and expecting 8 bytes. It also appears that whatever messeage immediately follows the DM1 on the bus is what is used by the application to fill in the "missing" bytes. This would explain the randomness of the SPNs shown. This is only a theory right now, but should be able to be tested by sending a 2 byte DM1 message followed by known messages and looking for the pattern.

Regardless, the DM1 application should be re-evaluated to prevent this behavior.

This issue currently has me at a standstill.

This is now corrected in 2.2 Patch 1