Capacitive Touch Button by using ADC channel (the CVD system)

[ivanrosales]

Returning to the mister_e's idea of the USB 8-pin chip, I wish to see that too!
You can do a lot even with NO extra I/O pins: http://www.thinkgeek.com/interests/retro/c208/

[Max Power]

Hank, awesome. you -seriously-made my day. I'm picking up the 12F1822, and 16F1823s this afternooon, and I should be up and running in no time. will I have to modify my DT file like you did a while back? I can't find that post right now.

[rmteo]

You can read multiple touch buttons (and perform other functions at the same time) with a PIC16F690/88/887 type device. This example does the keyboard scanning (30+ keys), polyphonic tone generation, PWM, etc. with a single PIC all concurrently.

[HankMcSpank]

Ok, my process abpove was right, but the code snippets were riddled with errors (on account I used Timer1 in my code)...I actually spotted one more, so pay no attention to the code snippets above! Here's another attempt below, not saying it's error free (on account again, it's a hack), but use it as a starter, then come back if you've problems...

(this is for a 12f1822, but the concept is the same for its larger brothers...as are most of the registers - this was just a direct copy of my fuse settings....they may need tweaking to suit your own config)

@ __CONFIG _CONFIG1, _FCMEN_OFF & _FOSC_INTOSC & _WDTE_SWDTEN & _MCLRE_OFF & _CP_ON & _IESO_OFF & _BOREN_OFF & _PWRTE_OFF
@ __CONFIG _CONFIG2, _LVP_OFF
'
DEFINE  OSC 8                'tell picbasic what speed the oscillator is
'
INCLUDE "DT_INTS-14.bas"     ' 
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts
'
Osccon = %01110010     'sets the internal oscillator to 8Mhz
'
TRISA.0  = 1    . 'make pin 7 (RA1) CPS0 analogue
ANSELA.0 = 1      'make pin 7 (RA1) CPS0 as input
'
OPTION_REG = %10000111 'use timer0 as interrupt (timebase) TMR0 Prescaler on (bit3) 256:1 prescale value (bits 2-0)
'
CPSCON0 = %10001101    'set the CPS module highest frequency availabe (fo vcc mode) + timer0 clock sourced from CPS module. (BIT 1)
'
CM1CON0 = 0   ' COMPARATOR OFF
CM1CON1 = 0   ' COMPARATOR OFF
'
CPS0_PRESENTCOUNT  var word
CPS0_THRESHOLD   var word
CPS0_LASTCOUNT   var word
 '
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR0_INT,  _Timer0_Int,   pbp,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM
 '
TMR0 = 0                 'clear down TIMER0
@ INT_ENABLE  TMR0_INT  'enable timer0 interrupts
' 
main:
pause 100
goto main
'
'**************************************************************************************************
Timer0_Int:
@ INT_DISABLE  TMR0_INT   ' stop timer0 interrupts while we're in here
CPS0_PRESENTCOUNT = TMR0     ' take a snapshot of Timer0's present count.
CPS0_THRESHOLD = CPS0_LASTCOUNT - ((CPS0_LASTCOUNT/100)*2)   ' this sets the 'trigger' up for a 20% diversion (finger press)
CPS0_LASTCOUNT = CPS0_PRESENTCOUNT ' store away the present timer0count for the next time we come into the interrupt routine
if CPS0_PRESENTCOUNT <  CPS0_THRESHOLD then 'if the present incoming timer0 count is 20% below the last count, then a finger has been placed on the sensor - go do 'stuff'
blah blah   
 
TMR0 = 0 ' clear timer0 down
@ INT_ENABLE  TMR0_INT  ' re-enable interrupt
@ INT_RETURN
end

One unknown, is the timer0 prescaler - you may need to tweak this (the OPTION_REG = %10000111 entry) to keep your oscillator under a count of 255 between successive timer0 interrupts (else timer0 will overflow & you'll have one helluva time trying to trap a finger press!). Actually it's better to use timer1 as the timer to count the CPS oscillator output pulses....since it's 16 bits and gives you more room to play with, but I can't be bothered to rejig the above....just consider iot as a framework to start from!

one thing I *strongly* recommend, is getting some debiuug/serout/hserout/pickit2uart tool going down onto your PC screen ...just so you can see/confirm what you CPS oscillator counts are ....or you'll be grabbing int the dark.

[HankMcSpank]

Oh, and btw...I still consider myself a learner, so any hilarious lines or approach in my code - kindly go easy!! (just thought it worth sharing to save some of you all a bit of time)

[rsocor01]

Talking about different chips with CSM capability, lately I have been using the 16F1938/9 chips. They have more programming memory than the chip mentioned above, the 16F1825/9. I was running out of programming memory in my projects with the 16F727.

[HankMcSpank]

Clearly I was having a bad day yesterday ...as Max Power extablished & pointed out on this thread... http://www.picbasic.co.uk/forum/show...486#post107486 in my above snippets, I used timer0 for both the interrupts AND the CPS oscillator pulse counting - OOPS! So best check out his thread for the corrections.

Sorry about that etc.

[Nicmus]

So Rene,

Are you getting closer to wrapping up your project and post it here?
It could save many members a lot of headaches and will catch everybody’s attention as a well crafted piece of code that shows how much a little PIC can do.

Nick