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Ideas and thoughts about a 2 knob control approach for the PIC oscilloscope

Ideas and thoughts about a 2 knob control approach for the (PIC) oscilloscope Well you know how it goes, I looked, I thought 'It has enough pins (this PIC)' so it will drive the graphics (I am talking about a 16F690, and 64x128 LCD), have 2 analog inputs, a trigger input, huh, but only 20 pins, minus supply makes 18.

IO expanders is cheating, and I already have the PICs.

So to find a nice quick system to set the following things, with only TWO IO pins left free ;-)

gain ch1, gain ch2, trigger level, trigger polarity, trigger mode, pos ch 1, pos ch 2, timebase speed, timebase vernier, etc.

Now what I came up with is this (and I will have to use it, so it better work):

2 potentiometers on 2 analog inputs of the PIC -FOR ALL CONTROLS-.

The list above displayed on the bottom of the graphics LCD like this: CH1 CH2 tr. level tr. source etc

5mV/div 100mV/div -1 CH1

A B C D E Now turning one potentiometer (pot1) selects horizontally either A, B, C, D, E, etc (possibly highlighted), and you can quickly move between settings.

The other potentiometer sets the value for the selected item. So if for example A is selected, then turning pot2 switches from 2mV to 10mV to

50mV etc, Some items are adjusted continuous (like trigger level), and some in steps (like trigger polarity).

I have come to the conclusion that this way of controlling is very very fast, only requires 2 analog knob turns for every control, one if you stay with a control.

------------------------------------ | | | |

Reply to
Jan Panteltje
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pos ch 2, timebase speed, timebase vernier, etc.

E, etc (possibly highlighted),

to 50mV etc,

(like

control.

then

IIRC there is a scope that does the same, except that it uses rotary pulse encoders instead of a potmeter. So there might be prior prior art ;-)

--
Regards, Joerg

http://www.analogconsultants.com/
Reply to
Joerg

On a sunny day (Fri, 11 Jan 2008 15:08:30 -0800) it happened Joerg wrote in :

pos ch 2, timebase speed, timebase vernier, etc.

work):

E, etc (possibly highlighted),

to 50mV etc,

(like

control.

then

mm, yes, that is possible, in that case you are out of luck if they also patented potentiometers. But why pulse encoders? The PIC ADC is 10 bits, there is visual feedback, if too many items, then I can perhaps software scroll the list horizontally.

Anyways, I have invented the wheel many times, now just imagine if somebody patented that wheel !

It is my attempt to open source hardware.

PIC is a bit of a beast to do this, I have a nice char set (6x9), it will fit, but all those banksels and page selects are eating code space.

Reply to
Jan Panteltje

"Jan Panteltje" a écrit dans le message de news:fm8tbm$8pc$ snipped-for-privacy@aioe.org...

oscilloscope

(this PIC)'

LCD),

supply

TWO

ch 1, pos ch 2, timebase speed, timebase vernier, etc.

better work):

C, D, E, etc (possibly highlighted),

10mV to 50mV etc,

steps (like

fast,

with a control.

patent it, then

;-)

horizontally.

outch, I was afraid you were serious...

Vincent

formatting link

Reply to
vincent.thiernesse

pos ch 2, timebase speed, timebase vernier, etc.

etc (possibly highlighted),

50mV etc,

control.

then

No buttons! Yahhh! Death to buttons on instrumentation! :P

D from BC British Columbia Canada.

Reply to
D from BC

PIC)'

pos ch 2, timebase speed, timebase vernier, etc.

work):

E, etc (possibly highlighted),

to 50mV etc,

(like

control.

it, then

Potmeters are notoriously unreliable. They are ok for a few years, then the wiper starts exhibiting the occasional "lift off". Encoders last a whole lot longer although the one in my lab receiver is totally short in the bearings now :-(

[...] 
--
Regards, Joerg

http://www.analogconsultants.com/
Reply to
Joerg

On a sunny day (Sat, 12 Jan 2008 00:23:24 +0100) it happened "vincent.thiernesse" wrote in :

I am always serious :-)

Vey nice Vincent!

Reply to
Jan Panteltje

On a sunny day (Fri, 11 Jan 2008 15:25:32 -0800) it happened D from BC wrote in :

pos ch 2, timebase speed, timebase vernier, etc.

E, etc (possibly highlighted),

to 50mV etc,

(like

control.

then

:-)

Reply to
Jan Panteltje

"Jan Panteltje" a écrit dans le message de news:fm8u32$ami$ snipped-for-privacy@aioe.org...

thanks !!!

Reply to
vincent.thiernesse

On a sunny day (Fri, 11 Jan 2008 23:28:24 GMT) it happened Joerg wrote in :

oscilloscope

PIC)'

1, pos ch 2, timebase speed, timebase vernier,

work):

D, E, etc (possibly highlighted),

10mV to 50mV etc,

(like

fast,

control.

it, then

True, I have a big power audio amp, and always before I use it I have to turn the left channel pot back and forwad a few times. Else it is crrr crrrr if you change volume. But it is a 300W (RMS) amp in 19 inch and did cost only 65 Euro. They must have saved somewhere. LOL

Reply to
Jan Panteltje

pos ch 2, timebase speed, timebase vernier, etc.

etc (possibly highlighted),

50mV etc,

control.

then

Small complication: the pot2 position can't absolutely set a value (ie, you can't just read the adc and poke the parameter) because if you did that, sweeping pot1 across the variables would set them all as you pass. So pot2 action has to be incremental. But a pot, unlike an encoder, runs out of rotation.

John

Reply to
John Larkin 

--
I disagree.  Since the output of the ADC will inherently be
incremental, all you have to do is compare the output of the ADC now
with a few earlier samples and if they\'re all the same, then that\'s
the value you use.

"Debouncing" the pot, if you like.
Reply to
John Fields

Hi Jan,

I would like to know, how will these two controls will handle the three channels you have on the left.

Adding an extra PIC to handle the user interface seems like a simple and modifiable solution.

formatting link

The center switch can be use to select options and menus.

donald

Reply to
donald

pos ch 2, timebase speed, timebase vernier, etc.

work):

E, etc (possibly highlighted),

to 50mV etc,

(like

control.

then

Depends on the torque you apply :-)

The code could require that once pot1 rests on a desired variable you need to wiggle pot 2 ever so slightly to make a value "stick". Also, there used to be infinite rotation pots for the old quad audio systems. But they might be gone or boutique parts now.

--
Regards, Joerg

http://www.analogconsultants.com/
Reply to
Joerg

PIC)'

pos ch 2, timebase speed, timebase vernier, etc.

work):

E, etc (possibly highlighted),

to 50mV etc,

(like

control.

it, then

But then it would jump to some essentially arbitrary value, corresponding to the existing angular position of the pot. That would be very annoying in practise. Imagine shifting, say, the ch1 and ch2 vertical positions a bit. Or changing the timebase. It's hard to imagine a function that wouldn't be a nightmare in this mode.

Early digital scopes had just a few buttons and maybe a spinner knob. We demoed one HP scope that nobody could get to work. Even digital scopes now have lots of different knobs for the various channel, trigger, and timebase functions.

John

Reply to
John Larkin

The other problem is that pots have a 'memory'--if you have the horizontal position cranked, when you switch from 'position' to 'sensitivity' mode, your time base just went from 1 us/div to 1 ms/div. Could get old.

Encoders, being differential, don't mess up your default position.

Something like an iPhone display would be sort of cool--to change the horizontal scale, just put two fingers on the screen and move them further apart or closer together. I'd definitely want knobs, though (and probably Windex after an hour or so).

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

oscilloscope

PIC)'

1, pos ch 2, timebase speed, timebase vernier, etc.

work):

D, E, etc (possibly highlighted),

10mV to 50mV etc,

(like

fast,

control.

it, then

Was that the boat anchor 12-bit 10 MHz digitizer with a separate display unit (like an old spectrum analyzer)? The one where you had to drill down 3 menu levels to set the vertical gain?

I found one of those in the hallway at work once, in like 1988--it was nearly new. I was overjoyed, until I spent a whole afternoon trying to make it work. Then I put it back in the hallway.

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

oscilloscope

PIC)'

LCD),

1, pos ch 2, timebase speed, timebase vernier, etc.

work):

D, E, etc (possibly highlighted),

10mV to 50mV etc,

(like

fast,

a control.

it, then

No, it was one big unit, fairly fast, but impossible to operate.

I read that Seico or somebody started making digital watches that had a single pushbutton to set the time. Something approaching half of them came back from customers who couldn't.

Our new Keithley 2100 DVMs are nightmares. The default setup is almost unusable, the menus to change things are incredibly obtuse, and the settings *can't be saved*. I never turn mine off.

John

Reply to
John Larkin

control.

You should test it yourself. I have used a one-knob control of some AES3/SDI encoder at a clients site and for some people it is very difficult to use and I don't like it, because it is too slow: you have to skip serially through many menu items and it has a deep hierarchy (the knob is pressable to enter a menu branch and to select a setting), which doesn't help to make it easier.

I think the best is a touch screen, because after some time you know the images and positions of the virtual buttons and you can touch the right positions very fast (like I can do it with the railway ticket machine).

Or simulate a touch screen: Show some buttons on the screen and mount some real buttons to the side of the screen. Then you can change the meaning of the buttons, like implemented in my Tek and like I've seen for some Agilent scopes.

But don't forget to add some dedicated buttons for functions you need often, like run/stop, single seq. etc. It would be very unusable to use a scope with only two potentiometers and every time I need start/stop I have to turn two knobs. So, please cheat, and use an IO expander :-) Or even better: use a PIC like the PIC18F252, which has 25 IOs and you can get it for §7.68 for single units at Digikey, which is only twice as much as the PIC16F690, but you'll get more than twice as much performance, flash, RAM etc.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
Reply to
Frank Buss

On a sunny day (Fri, 11 Jan 2008 15:47:49 -0800) it happened John Larkin wrote in :

then

I think this is not a problem John. The analog channels (pots) are continunously sampled. If only pot1 is used, and pot2 is not moved (no change in last value from pot2), then no changes will be made to any settings. The pseudo code for that is very simple, and you need only 3 vars:

int pot1; int pot2; int pot2_old = -1;

set_ch1_gain() { if(pot2 != pot2_old) { do_something_here(pot2); pot2_old = pot2 } } return OK;

To get the 'ladder' of analog values, first clip at the top:

if(pot1 > 4000) { set_ch1_gain(); return OK; } else if(pot1 > 3500) { set_ch2_gain(); return OK; } else .... etc etc

Or something like that. I was thinking, that you as perfect embedded ASM programmer, would know those tricks ;-)

Reply to
Jan Panteltje

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