Updating HPWM frequently, safe?

[peu]

mmm, could be a noisy pot as well... using your code and on many low-value ADC.. they are all stable.. no noise, no frlicker.

what happen if you stick a 0.1 uF in parallel with your POT wiper?

Any 0.1uF + 10uF capacitor close to your PIC?

I just tried with a 20 turn 10k linear pot and its the same, once I reach the lower duty cycles the led flickers.
The difference is clearly visible with the multiturn pot, once you go below a certain level it flickers, move the other way a little bit and the flicker goes away

Reading in the flicker position I get this range: from $00BB to $00BF and spurious $009F , $00B4, $00C6, $00E3 at random places
Reading in the steady position I get this range: $00CD to $00CF and no spurious readings

I only read 125 word values into the device own eeprom.
Again Im using a li-ion battery for powering the circuit (3.65v)

Weird isnt it? even weirder is that sometimes when I write the values to eeprom the written values are steady (also visually) but only when writting...

Just in case here is the code I used:

'       Pic Configuration
@ device pic12f683,INTRC_OSC_NOCLKOUT , wdt_on, mclr_off, protect_off        

'       Hardware configuration

'       I/Os
TRISIO = %00010010      ' pin1 is ADC , pin4 is the calibration button

'       ADC's
ANSEL = %00000010  
DEFINE ADC_BITS 10      ' ADCIN resolution  (Bits)
DEFINE ADC_CLOCK 1      ' ADC clock source  (Fosc/8)
DEFINE ADC_SAMPLEUS 11  ' ADC sampling time (uSec)                      
ADCON0.7 = 1            ' Right justified results

'       Comparator
CMCON0 = %00000111     ' Disable comparator
VRCON  = %00000000     ' disable
'cmcon0 = %00001110      ' Multiplexed Input with Internal Reference CIS=1
'vrcon  = %10001010      ' set vref=2.25v (from 4v input) 

include "HPWM10.pbp"

' definitions
pote 		var word
Frequency   var word
calibraled  var gpio.5
calibrapin  var gpio.4
conta       var byte

gpio=0
conta=0
frequency=1000
pause 50    ' coffee break

loop:

    adcin 1, pote
    if pote>1000 then pote=1000
    
if calibrapin=1 then
if conta < 250 then
 write conta, pote.byte1
 write conta+1, pote.byte0
 conta=conta+2
endif
endif

@ HPWM10  1, _pote, _Frequency
pause 10

goto loop
end

Pablo

[mister_e]

O.K. i have to go out. I had the same code, and i didn't have any problem...

when i'll be back, i'll use a lower voltage AND use HighBrightness LEDs.

Wish i could see the same thing....

Still thinking there's an hardware problem...

[Darrel Taylor]

Pablo,

Good new, Bad news.

I finally found my 12F683 and gave it a go.
I've completely duplicated your problem. Blinking and all.

For some reason it only does it on the 683.
Every other chip I tried seems to work fine.

And the bad news is, I haven't found out why yet. (Operative word, Yet)
It appears to be with the A/D, the readings are all over the place at low voltage input.

I still have many things to try, but just wanted you to know you're not crazy.
And, I WILL find it. (unless somebody beats me to it)
<br>

[peu]

Pablo,

Good new, Bad news.

I finally found my 12F683 and gave it a go.
I've completely duplicated your problem. Blinking and all.

For some reason it only does it on the 683.
Every other chip I tried seems to work fine.

And the bad news is, I haven't found out why yet. (Operative word, Yet)
It appears to be with the A/D, the readings are all over the place at low voltage input.

I still have many things to try, but just wanted you to know you're not crazy.
And, I WILL find it. (unless somebody beats me to it)
<br>

As I see it its only good news Thanks for all your efforts!!!

I can't help with your code, is way beyond my actual knowledge, I hope to catch up with it in the future!

Now I patiently wait


Pablo

[peu]

An EE friend of mine (Thanks Doug) told me a new possibility about the cause of the problem:

What if reading the ADC so often does not give it enough time to handle the low voltage values?

(more discussions via chat with my friend)

He points out something interesting, the test program initializes the ADC using:

DEFINE ADC_BITS 10 ' ADCIN resolution (Bits)
DEFINE ADC_CLOCK 1 ' ADC clock source (Fosc/8)
DEFINE ADC_SAMPLEUS 11 ' ADC sampling time (uSec)

But reading the pic basic manual we have:

ADC_SAMPLEUS is the number of microseconds the program waits
between setting the Channel and starting the analog to digital
conversion. This is the sampling time. The minimum number of
microseconds usable is determined by the minimum time for PAUSEUS.
See it’s section for this information.

and the PAUSEUS section says:

For 4mhz Minimum Delay is 24us

So, the initial theory appears to be right, I don't have the protoboard here now, but I will check this tomorrow.


Pablo

[Darrel Taylor]

I tried every AD oscillator / Sample time possible, and it made no difference.
Even with the A/D input tied directly to ground, it was getting crazy readings between 0 and 20.

After I tried it with a 12F675 (without the CCP) and got the same results,
I finally figured out that I had removed the big cap on the power lines on this protoboard.
Probably needed it for something else. Doh!

After putting a 100uf cap across the power supply, everything calmed down again.
It's still not perfect, but I think that has alot to do with the breadboard.

So then to really stabilize things I added an averaging routine, and I think that's about as close as we're going to get.

First make sure you have enough capacitance on your power lines (I think mister_e already suggested that).

Then add this to the bottom of the program

' -=-=-=-=-=-=  Average Analog values -=-=-=-=-=-=-=-=-=-=
Avg       VAR WORD
AvgCount  CON 16
spread    CON 20

Average:    ' Smooth data
    IF ABS (pote - Avg) > spread then
        Avg = pote
    else
        Avg = (Avg*(AvgCount-1)+pote)/AvgCount 
        pote = Avg                               
    endif
Return

And also, just after the ADCIN statement, add this

    gosub Average

HTH,

[mister_e]

it's getting interesting... i have everything on hand, will do some test here.

Sorry, i was suppose to do it yesterday