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Topic: Status flashing sequences (Read 1 time) previous topic - next topic


Sometimes when working with standalone boards (ie you don't have the opportunity to read diagnostics written to serial) it is helpful to use LED flashing sequences to indicate status of setup, looping etc. Say two longs for file setup failed, or 3 short (ie Morse for "S") to indicate success  This is pretty easily programmed into the Arduino by getting the Digital pin 13 onboard LED to let you know what is going on.

Have there been any attempts to standardize particular flashing sequences? I would imagine that situations are pretty much unique calling for different patterns, but some individual signals might fall into a common category.


I've never heard of such standardization - I've seen motor controllers that flash an LED N times for fault-condition number N - every application is going to have different error states, the only commonality being that something exceptional has happened.

Flashing the error string in morse code would be overkill I think!
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Udo Klein

A real overkill would be to encode the error string in manchestercode and then use this as a carrier for encoding the same string in morse code. Flashing something like this is an overkill ;)
Check out my experiments http://blog.blinkenlight.net

Coding Badly

Have there been any attempts to standardize particular flashing sequences?

Probably the closest thing to a standard for something like this are BIOS POST codes.

you don't have the opportunity to read diagnostics written to serial

Why not?  Sounds like a nice simple Arduino project... Arduino + LCD display + NewSoftSerial = simple dumb terminal.  Throw in an infrared transmit / receive pair an you have a "no touch" dumb terminal.


Thanks for the suggestions. The BIOS POST codes led me to:


which has interesting alternatives. Some of these are Morse-like in that they consist of 3 or 4 grouped shorts and longs.
I'm not overly impressed with the idea of say nine, ten, eleven shorts in a row, much room for error. I've no doubt Marconi considered a scheme with 1 spark for A and 26 sparks for Z. Also found other pages for different devices each with their own scheme, many based on Morse like sequences.

My application for this is a standalone UNO+SD - if in setup I can do my diagnostics and at the end of that ping out 3 short flashes for success then that will be enough to reassure me that it's doing its thing. After that I am confident it will keep on track. I have already found that pin 13 is bad for this signalling, as soon as the SD is initialized it seems that pin 13 is taken over since flashes become garbled. Pin 8 seems to be ok with its own LED+resistor.

I envision at least a few useful common codes:
three shorts for end of setup and successful launch into loop(),
continuous wide spaced single shorts (Morse E) for fatal error (the BIOS POST continuous tone is not a good idea unless it is warning of nuclear attack),
a long and two shorts (D) might indicate a disk error, plug in card, etc.

Yet another application-specific scheme I guess.

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