Need 4 modes with just 3 switches - need all modes to be selectable QUICKLY!

[HankMcSpank]

Hi Guys,

here's my conundrum.

I'm knocking up a guitar widget that has four modes - becuase the unit needs to be physcially small, I can only shoehorn 3 momentary switches into it.

Ok, so at the moment, I've arranged 'user interface' as follows...

Switch 1 pressed quickly = mode 1
Switch 2 pressed quickly = mode 2,
Switch 3 pressed quickly = mode 3, pressed and held for 250ms = mode 4.

(all switches use interupts - thanks Darrel! )

ok, no problems....ie I've got four modes out of the three switches - *But*...I don't know if you've ever played a guitar, but in mid Steve Vai-esqe solo (I wish!), that Switch3 200ms press & hold to select mode 4 seems like a lifetime waiting. Also, I reckon that mode 4 won't be actually used that often, but presently when selecting either mode 3 or 4, the program pauses 250ms (to see if the switch has been held down), before deciding whether it's actually mode 3 or mode 4 that's required...this means that mode 3 is held back when selecting too - there has to be a slicker way of doing this!

So, I'm now thinking about rather a press & hold for mode 4, you press Switch3 twice in quick succession (& bringing a timer into play)

I was just wondering what the more experienced among you think about the viability of getting the speed of 4 mode selection with 3 switches down to lightning fast levels?

[Kamikaze47]

I assume the switches are right next to eachother? if so, why not make it so that mode 4 can be activated by pressing 2 and 3 at the same time. To do this i would suggest that for the interrupt handler for switch 3, have a quick loop that checks button 2 for a short time (something like 20ms). If it is pressed, activate mode 4, else activate mode 3.

The "double click" can be done too, but requires a bit more logic and probably a timer.

[HankMcSpank]

I assume the switches are right next to eachother? if so, why not make it so that mode 4 can be activated by pressing 2 and 3 at the same time. To do this i would suggest that for the interrupt handler for switch 3, have a quick loop that checks button 2 for a short time (something like 20ms). If it is pressed, activate mode 4, else activate mode 3.

The "double click" can be done too, but requires a bit more logic and probably a timer.

Thanks for your input...I'd pondered that option - and yes the switches are near each other - but I worry a little over the actual logistics. A guitarist will be selecting these switches with his right hand - this will already have a plectrum in it (between the thumb and forefinger), this leave him needing to press two switches concurrently but with two fingers partially out of action - then there's the accuracy at landing fingers on two small (3.5mm diameter) button tops 'on the fly' in mid solo etc on a dimly lit stage etc.

[Bruce]

How about using 1 switch as the mode switch? Use a toggle switch to select how the other 2 switches act.

Mode switch = 1, other two act as switches 1 & 2. Mode switch = 0, other two act as switches 3 & 4.

Or use a normally open mode switch. Press once, in mode 1. Press again, in mode 2.

Kind of like the Shift key on your keyboard that doesn't need to be held down to select other key functions.

[Kamikaze47]

In that case the double press is probably the best option. Something like this:

button3 interrupt handler:

IF timer is not running THEN
set timer so it will overflow after x time (max double click time), and start timer running
ELSE
set to mode 4
stop timer
ENDIF

timer interrupt handler:

set to mode 3
stop timer

[HankMcSpank]

Bruce,

Thanks for the idea - I'm unable to use a toggle switches (though I'd have loved to have), because this PIC/PCB/Switches are going in a small control box with just 5.5mm headroom inside (just under 1/4"" in old money)....also the control box will affixed to the guitar body with four small adhesive pads - a toggle switch would mean the player would be applying force 'sideways' on the switch (with respect to the control box surface), which could place some stress of the adhesive fixings whereas momentary switches, the force will be down (ie pressing the adhesive pads down).

Kamikaze47,

i'm not a programmer...& this stuff doesn't come naturally to me....but thanks for the example to get me started, I'll see how I can weave that concept into my code over the next day or two.

[Kamikaze47]

Kamikaze47,

i'm not a programmer...& this stuff doesn't come naturally to me....but thanks for the example to get me started, I'll see how I can weave that concept into my code over the next day or two.

Give it a try, and if you get stuck, post the code you have written here and we can help.