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ttlappalainen / NMEA2000

NMEA2000 library for Arduino
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Rx buffer in NodeOnly mode #379

Open greenhouse69 opened 5 months ago

greenhouse69 commented 5 months ago

A conceptual question, in tNMEA2000::N2km_NodeOnly mode (I understand it is Tx only), shouldn't I implement the Rx buffers: NMEA2000.SetN2kCANMsgBufSize(6); default 5 messages. NMEA2000.SetN2kCANReceiveFrameBufSize(250); And yes, for the TX one: NMEA2000.SetN2kCANSendFrameBufSize(250);

I have seen some examples, in NodeOnly mode, implementing all 3 buffers: NMEA2000.SetN2kCANMsgBufSize(6); NMEA2000.SetN2kCANReceiveFrameBufSize(250); NMEA2000.SetN2kCANSendFrameBufSize(250);

Which is correct? Thanks.

ttlappalainen commented 5 months ago

Unfortunately this is very historical mode idea and a bit confusing. The only difference between N2km_NodeOnly and N2km_ListenAndNode is that N2km_NodeOnly does not forward messages. Forward can be disabled with EnableForward(false) which makes N2km_NodeOnly unnecessary.

Only N2km_ListenAndNode and N2km_ListenAndSend are necessary. N2km_ListenAndNode for bus device and N2km_ListenAndSend for reading bus or fooling.

greenhouse69 commented 5 months ago

I understand that for N2km_NodeOnly mode, RX buffer is not necessary, is that correct? Thank you very much for your help.

ttlappalainen commented 5 months ago

Yes it is. As it does all required communication with bus as N2km_ListenAndNode, Rx buffer is important. If there is not enough Rx buffer, device tries to work, but works half way. As I said: "The only difference between N2km_NodeOnly and N2km_ListenAndNode is that N2km_NodeOnly does not forward messages. Forward can be disabled with EnableForward(false) which makes N2km_NodeOnly unnecessary."

greenhouse69 commented 5 months ago

So:

NMEA2000.SetMode(tNMEA2000::N2km_NodeOnly, 30);

equals

NMEA2000.SetMode(tNMEA2000::N2km_ListenAndNode, 30); NMEA2000.EnableForward(false);

Can be used interchangeably. That N2km_NodeOnly not being necessary doesn't mean that it's better to use N2km_ListenAndNode + EnableForward(false), or are they independent? Thank you for your clarification and your patience.

ttlappalainen commented 5 months ago

Yes can be used interchangeably before open but not after. SetMode must be called before open and it can not be called after. There actually should be limitation so that it does not do anything after open. As I mentioned, there is some historical reasons.

I personally use

NMEA2000.SetMode(tNMEA2000::N2km_ListenAndNode, SourceAddress);
NMEA2000.EnableForward(false);

With ESP32 I can then command via WEB interface during runtime.

NMEA2000.SetForwardStream(UDPStream);
NMEA2000.EnableForward(true);

And use the NMEA Simulator for reading bus data.

greenhouse69 commented 5 months ago

Great! Now I understand. It's better not to limit oneself with NodeOnly. Thank you very much. (I hope you can forgive my ignorance on these matters. Very grateful.)