Actually - I just looked through an example over 
at: https://www.hackster.io/doug-domke/multiplexed-nixie-tube-clock-759ff5

... and it all seems fairly understandable, have I overthought this?

 - Richard


On Wednesday, 1 November 2023 at 09:22:03 UTC Richard Scales wrote:

> The time has come when I need to get a handle the dark and mysterious art 
> of multiplexing.
> I have an understanding of what needs to happen though am mostly at a loss 
> of how to implement it.
> I am broadly assuming that I should be using some kind of interrupt 
> routine to make the actual display work whilst the rest of the code gets on 
> with the job of working out what to display and when to display it.
> Is it even going to be feasible to have some kind of interrupt routine 
> that decides what digits to light - set all the bits and then sets the 
> right anode(s) on and then off again giving enough time for the persistence 
> of vision to produce a non flickering display when using something like a 
> wemos D1?
>
> I am thinking that the interrupt routine needs to increment which digit(s) 
> is/are being illuminated - set up the right bit pattern for the cathodes 
> and turn on the relevant anode(s) - wait a little and then turn them off 
> again. 
> My worry is that the amount of time that the displays should be left on 
> might be a little too long for the ISR as my understanding is that these 
> should be kept as lean as possible.
>
> Do I even need multiple interrupts (my covid addled brain is struggling to 
> type let alone contemplate multiple ISR's!)?
> Can the rest of my code run in a non time critical manner as it works out 
> what it wants to display where whilst the interrupt routine merryly 
> illuminates digits based on values which I store in a buffer somewhere? 
> ... or does the rest of my code have to work in come kind of state-machine 
> fashion?
> I would expect (hope) to handle display brightness via PWM signals to HV 
> Drivers. 
> I have no need for cross fade effects either - just basic multiplexing of 
> say 10 different multi segment displays. I am more than happy to break up 
> the displays into say 2 (or more) groups in order to makes things a little 
> easier.
>
> Can anyone point me in the right direction - ideally with some code 
> snippets that I can use as a foundation?
>
> Just to confirm, it is only the general implementation  to drive the 
> displays that eludes me - the rest of the clock code is well defined and 
> working well in a direct drive capacity.
>
> The desire to move to multiplexed operation is born out the the desire to 
> drive a greater number of displays with a greater number of segments which 
> could be done via direct drive but I foresee that multiplexing the displays 
> will simplify the electronics required.
>
> So many questions I know. I would be grateful for any pointers, thank you.
>
>  - Richard
>
>

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