I am trying to understand how F3 horn play packet commands work.
I know the basic functions 1-4 are in Function Group One as described in the extended packets document ( https://www.nmra.org/sites/default/files/s-9.2.1_2012_07.pdf line 258) When a command station send an F3 horn play command, does the short horn (when mapped to F3) play ONLY when it receives on ON command? Does it also play when it receives an OFF command? Is the decoder expecting to receive an OFF command following every ON command (prior to receiving the next Short Horn F3 On command)? It was my impression that typical command stations send out many copies of each packet command, so it wouldn't make sense for the Short Horn to play every time it receives in F3 On command (or it would risk playing over and over).
And since F3 is in Function Group One, it wouldn't make sense for the Short Horn to play when it receives an OFF command (so it doesn't play every time you turn the bell ON/OFF)
Any insight in understanding this would be appreciate.
Unless someone designs or otherwise works to create decoders, I don't think they really ever get into 'packets' and all that. It's not something a model railroader is usually (ever?) going to be working with or adjusting.
FWIW a few function buttons are normally 'latching', the function turns on when the button is pressed, and remain on until the function button is pressed again to turn them off. Most common is F0 (lights) and F1 (bell); some decoders add a latching function button for dynamic braking sound (often F4).
If the decoder uses long and short horn on separate function buttons, the short horn (normally F3) is set to a kind of momentary contact - the horn sounds for a set time, regardless whether you hold the function button down or not.
The others are normally set to only work when the function button is actually being depressed. For example F2 is normally the whistle/horn (or long horn/whistle, if F3 is the short horn). The horn sounds as long as your finger or thumb is pressing down F2, and stops when you release it.
different commands from a controller can be interpreted differently by the command station and decoder
at least for NCE, the controller simply sends button presses which the command station interprets as commands. for example, the sequence of Select # # Enter is interpreted as a command for setting the loco address being controlled by that controller. subsequent speed commands from that controller, either +/- button presses or knob updates are used to adjust the speed in the speed packet repeatedly sent to the loco by the command station even if the controller is unplugged.
i noticed recently that Digitrax horn button (f3?) seems to control the duration of the horn, the horn being on as long as the button is held down. this being the case implies that each sending of the horn button causes the decoder to maintain the horn on for some period of time long enough to receive another horn packet. Or maybe it sends on ON when the button is pressed and an OFF when released
don't know if this is a feature of the command station or the decoder.
greg - Philadelphia & Reading / Reading
Just typed a long reply and pressed send. That F#$&@-+*N 403 forbidden popped up and it's gone!!!!!!! Mad face, mad face, mad face.
I'm guessing the decoder simply activates the short horn every time the status of F3 changes. So say F3 is off; you hit F3, and it turns on F3, and the horn honks. The command station can keep spitting out "F3 is on" commands til the cows come home but there will be no honking until you hit F3 again, turning F3 off, and provoking another honk.
This would also allow you to hold down F3 for a continuous horn. The command station would be sending out constant packets alternating F3 on and F3 off, restarting the short horn every time. As long as the short horn duration is longer than the command station's debouncing, the result is a continuous horn.
Just speculation though, can't confirm... I had a DCC packet sniffer on a breadboard a couple years ago but it is since dismantled
I'm gonna try this again. I'll shorten it up though.
How long the short horn blows is in the programming of the decoder. Unless your throttles F3 key is set to momentary the horn will blow every time you press the button. Most throttles have latching F3 buttons. The horn will blow once when it reciever an on command. There should not be a horn command when you press F3 again unless the firmware and software in the decoder is programmed to blow once on the off command.
Holding the F3 will not keep the horn playing. Short horn sound slot is just that. Short horn.
There are playable whistles. But those use the momentary whistle/ horn key. I suppose you could remapp to F3 but I can't see it working too good.
Pete.
I have a Lenz system 100. There is a stack which holds 32 addresses, and you can use them for individual locomotives or consists. You can program each function key to be either momentary or latching. That's convenient for these odd cases.
It takes an iron man to play with a toy iron horse.
Normally F2 or F3 are not 'latching', F1 (bell) is latching. When you press F1, the bell starts ringing, and it only stops when you press F1 again. F2, horn/whistle, works by contact - as long as you hold the button down, the horn or whistle blows. F3 normally is like a momentary contact - you press F3 and the short horn sounds once. Holding F3 down should not make the short horn blow continually the way F2 would make the long horn blow.