Checks for pgn that is no longer active

[mar0997]

Hi Timo -

I continue to appreciate your work on the library and I have expanded my code significantly. One thing that I have done is to create a new library based on your work that adds AC parameters 127744 - 127748 that I read from my Victron equipment. I also added AC parameter 127503 that I then output to be read by my Czone equipment. In addition to being able to now read the AC data by Czone I also add my 2 AC lines to get a total AC input to my boat.

This works great under normal situations when I am plugged into shore power or running my generator. The issue that I have not been able to solve is that the AC data continues to show the last value when AC power is removed. I have tried a variety of things to attempt to resolve this. I assume it is something simple and it may or may not be related to the new library that I created.

Using DataDisplay2 as an example I have tried this approach:

void ACVoltFreqB(const tN2kMsg &N2kMsg) {
unsigned char SID;
unsigned char ConnectionNumber;
double ACRMSvoltageLtoN;
double ACRMSvoltageLtoL;
double ACFrequency;

if (ParseN2kACVoltFreqB(N2kMsg, SID, ConnectionNumber, ACRMSvoltageLtoN, ACRMSvoltageLtoL, ACFrequency) ) {
Line2Voltage = ACRMSvoltageLtoN;
Line2Frequency = ACFrequency;
}
else {
Line2Voltage = 0;
Line2Frequency = 0;
}
}

I have also tried the approach of comparing the SID to the previous SID and if has not changed for a period of time to set the parameters to 0:

ParseN2kACVoltFreqB(N2kMsg, SID, ConnectionNumber, ACRMSvoltageLtoN, ACRMSvoltageLtoL, ACFrequency); {
CurrentSID = SID;
Line2Voltage = ACRMSvoltageLtoN;
Line2Frequency = ACFrequency;

  if (CurrentSIDLastState != CurrentSID)
  {
    startAC2timer = millis();
    CurrentSIDLastState = CurrentSID;
  }

  if (millis() - startAC2timer >= 500 )
  {
    Line2Voltage = 0;
    Line2Frequency = 0;
  }

}

Both of these work fine when AC power is active. But when AC power is removed I expect that the voltage and frequency go to 0, but instead both stay at the last values prior to removing power. I have verified with my analyzer that the Victron equipment stops transmitting the pgn when I remove AC power so I'm stumped as to why neither of these work. Can you offer me some advice?

[ttlappalainen]

It is because your ACVoltFreqB will be never called after generator has been stopped and message will not be sent anymore. You have to do it like this:

static uint32_t AC2timer = 0;
static double Line2Voltage = 0;
static double Line2Frequency = 0;
#define ACTimeout 5000

void CheckTimeouts() {
  if ( millis()-AC2Timer > ACTimeout  ) {
    double Line2Voltage = 0;
    double Line2Frequency = 0;
  }
}

void ACVoltFreqB(const tN2kMsg &N2kMsg) {
  if ( ParseN2kACVoltFreqB(...) ) {
    ...
     AC2timer = millis();
  }
}

void loop() {
  NMEA2000.ParseMessages();
  CheckTimeouts();
  ...
}

[mar0997]

Thank you Timo! This makes sense to me. I got tripped up on DataDisplay2. With a small adjustment this works. I really appreciate your help.