16F726 Capacitive sensing module

[Darrel Taylor]

I don't see the "Timer 1 Gate Event Interrupt" listed in the Available Interrupt Sources on your website Darrel.

Yeah, it's not in there.

But it's not too hard to add it to the DT_INTS-14.bas file....

ASM
  #define TMR1GATE_INT   PIR1,TMR1GIF     ;-- Timer1 Gate Interrupt
  #define INT_INT   INTCON,INTF     ;-- INT External Interrupt
  #define RBC_INT   INTCON,RBIF     ;-- RB Port Change Interrupt
  #define TMR0_INT  INTCON,T0IF     ;-- TMR0 Overflow Interrupt 16F
  #define TMR1_INT  PIR1,TMR1IF     ;-- TMR1 Overflow Interrupt
...

and

GetIntInfo  macro  IflagReg, IflagBit

Found = NO
; nolist
  ifdef TMR1GIF    ;----{ TMR1 Gate Interrupt }---------------[PIR1, TMR1GIF]---
      INT_Source  PIR1, TMR1GIF, PIE1, TMR1GIE
  endif
  ifdef INTF    ;----{ INT External Interrupt }----------------[INTCON, INTF]---
      INT_Source  INTCON, INTF, INTCON, INTE
  endif
  ifdef RBIF    ;----{ RB Port Change Interrupt }--------------[INTCON, RBIF]---
...

<hr>
Then in your program's interrupt definition ...

'-----Set up Interrrupts
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1GATE_INT,  _CheckCount,   PBP,  yes
    endm    
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@ INT_ENABLE  TMR1GATE_INT     ; enable Timer1 Gate interrupts

Good Luck!

[AMay]

I made a capacitor checker using a 16F84A which works very well within limits. It uses the pot command. The code in PICBasic (not Pro) is:

' Capacitor Measurement
' Four digit common anode mulitplexed display
' Scan about 60/s (4ms pause)
' Driver 74HC4511
' Works for 2.0 uf (1K)- 100pf (20K)
' 8/20/06
' For 16F84A Chip
' Data output port A (Pin A5 NC)
' Pins 1 - 4 - Digit select for multiplex
' Pin5 - pot command
' Pin6 - Display Blanking signal (0 = blank)
' Pin7 - Range 1 = high value (1K resistor); 0 = low (20K)
' Digits 1 - 4; W1 - W4
' Measurement (Msr) W10
' Note that scan must be 60/s, and 1ms on + 3ms off shows no flicker, but
' leds are dim. 2ms on & 2ms off works well.
Settings:
Symbol Blank = pin6
Symbol Range = pin7
Symbol D1 = w1
Symbol D2 = w2
Symbol D3 = w3
Symbol D4 = w4
Symbol Msr = w10
Symbol PortA = 5
Poke $85, 0 ' Set port A to all outputs
Output 1 ' Digit 1 - MSD
Low 1 ' off
Output 2 ' Digit 2
Low 2
Output 3 ' Digit 3
Low 3
Output 4 ' Digit 4
Low 4
Output 6 ' Blanking
Low 6 ' Blank all segments


Start:
pause 750
Blank = 0
If range = 0 then testlow 'Check high or low state

'Testhigh:
pot 5,40,msr
Msr = Msr*10 'Raise results for 4 digit display
goto math

Testlow:
Pot 5,255, msr
Msr = Msr*100

Math: 'Set up digits in memory for display
D1 = Msr/1000
D4 = Msr//1000
D2 = D4/100
D4 = D4//100
D3 = D4/10
D4 = D4//10

Display:
poke porta, D1 'Send data
High 1 'Select Digit
Blank = 1 'Remove blanking
Pause 2 'Pause
Blank = 0 'Blank
Low 1 'Unselect digit
'Pause 2 'Pause again to save battery

poke porta, D2
High 2
Blank = 1
Pause 2
Blank = 0
Low 2
'Pause 2

poke porta, D3
High 3
Blank = 1
Pause 2
Blank = 0
Low 3
'Pause 2

poke porta, D4
High 4
Blank = 1
Pause 2
Blank = 0
Low 4
Pause 2
Goto display
end

[Byte_Butcher]

Bingo!
I changed my interrupt from TMR2/PR2 match to TMR1 gate event and it's working beautifully now. The count on the LCD now accurately reflects what's going on with the CSM oscillator.

Thanks so much for posting the necessary modifications to DT_INTS-14.bas.
I actually opened that file and had a look just before bed last night and had pretty much figured out to do the modifications you posted. Thanks for confirming it for me.

It looks like I need to adjust the TMR2 prescaler a bit to maximize the number of counts in the period, but it's working great now and the next thing to do is set up the averaging and "button pressed" detection routine but I think that should be pretty easy, even for me.

I'll post code when I've got it working well. I'm rather surprised no one here has played with the Touch Sensor module on the 16F726/7 yet....
I spent hours searching the archives and came up with a big zero.

Thanks again Darrel!

[Byte_Butcher]

Thanks AMay,
The capacitance checker may come in handy for me some time.

But what I'm working on isn't a capacitance meter, it's the Capacitive Sensing Module in the PIC 16F726/7's.

It's used to make capacitive "Touch Sensors" that detect a human finger without any buttons, just a simple conductive pad.

I think Darrel has got me up and running now.

[Byte_Butcher]

OK, I was gonna sit on this for a few more days until I had a chance to perfect it a little more, but here it is now in it's crude form. I'm sure it needs lots of fixing to be "good" code, but it's functional as is and hopefully will give a starting place for folks who want to play with the capacitive sensing module on the 16F72X PIC's. Please feel free to critique it and fix it up. I need the education...

This program sets up Capacitive Sensing pin0 (CPS0/RB0) on the 16F726 / 16F727 to be a "Touch Sensor" pin
When the sensor pad is touched, the raw count (from TMR1) will drop below the running average and a LED on PORTA.1 will flash. If the finger is held on the pad long enough, eventually the running average will catch up with the current value and the LED will turn off.

Relevant Data Sheets for the CSM module include:

http://ww1.microchip.com/downloads/e...Doc/41341B.pdf 16F72X / 16LF72X Data Sheet.
http://ww1.microchip.com/downloads/e...tes/01101a.pdf AN1101 "Introduction to Capacitive Sensing "
http://ww1.microchip.com/downloads/e...tes/01103a.pdf AN1103 'Software Handling for Capacitive Sensing"
http://ww1.microchip.com/downloads/e...tes/01171B.pdf AN1171 "Using the Capacitive Sensing Module on the PIC16F72X"

Crude Code follows.... Enjoy!

Steve

------------

'-------------------------------------------------------------------------------
'Trying to learn to use the Capacitive Sensing Module on a 16F727 --------------
'-------------------------------------------------------------------------------

@  __config _CONFIG1, _DEBUG_OFF & _PLL_EN & _BORV_2_5 & _BOR_ON & _CP_OFF & _MCLRE_OFF & _PWRT_EN & _WDT_OFF & _INTOSCIO
@  __config _CONFIG2, _VCAP_RA0

Include "MODEDEFS.BAS"    ' Include Shiftin/out modes
INCLUDE "DT_INTS-14.bas"  ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"  ' Include if using PBP interrupts

DEFINE LCD_DREG PORTA    ' Set LCD Data port
DEFINE LCD_DBIT 4        ' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_RSREG PORTA   ' Set LCD Register Select port
DEFINE LCD_RSBIT 2       ' Set LCD Register Select bit
DEFINE LCD_EREG PORTC    ' Set LCD Enable port                                                   
DEFINE LCD_EBIT 0        ' Set LCD Enable bit
DEFINE LCD_BITS 4        ' Set LCD bus size (4 or 8 bits)
DEFINE ADC_BITS 8        ' Set number of bits in ADC result
DEFINE ADC_CLOCK 3       ' Set clock source for ADC (rc = 3)
DEFINE ADC_SAMPLEUS 100  ' Set ADC sampling time in microseconds 
DEFINE OSC 8

OSCCON = $10         'set oscillator to 8 Mhz

TRISA= %00000000     'Set 'em all to outputs
ANSELA= %00000000	 'Set 'em all to digital
TRISB= %11111111   	 'all input
ANSELB= %11111111    'all analog
TRISC= %00000000     'Set portC all outputs   

CPSCON0 = %10001101  'Cap sense on, high range oscillator
CPSCON1 = %00000000  'Cap sense channel input 0 is selected

'-----Alias Pins
RW           var    PORTC.3 : LOW rw   'Read/Write for LCD
LED          var    PORTA.1      'LED to display when button is pressed

'-----Allocate Variables
timercount   var    word  ' raw count from TMR1
timerave     var    word  ' long term average of timercount
AvgCount     var    word : AvgCount = 32 'number of samples to average 

'-----Set up Interrrupts
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1GATE_INT,  _CheckCount,   PBP,  yes
     endm    
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@ INT_ENABLE  TMR1GATE_INT     ; enable Timer 2 interrupts

High LED
Pause 200       'Let the LCd wake up
lcdout $fe, 1   'Clear LCD
lcdout $fe, 2, " Awake! "
pause 500

'----- Timer Setup
T2CON = %01110110 'bit7=unimplemented, bit6-3=postscaler, bit2=TMRON, bit1-0=prescaler 
PR2 = %11111111       'give PR2 a number for TMR2 to match
PIR1.1 = 0      'Clear the TMR2 interupt flag
PIE1.1 = 1      'Turn TMR2 interrupt enable on
T1CON = %11000101 'Timer clock source=CAPOSC, prescale=1:1, dedicated OSC disabled, no external clock synchronize, timer on
T1GCON = %11100010 'Timer1 gate init/ Toggle Mode
PIR1.7 = 0   'Clear Gate Interrupt Flag
PIR1.1 = 0   'clear the TMR2 interupt flag

Goto main   'Just get it going...

'---[TMR2 - interrupt handler]--------------------------------------------------
    disable   
CheckCount:
    T2CON.2 = 0   'stop timer2
    T1CON.0 = 0   'stop timer1
    timercount = TMR1L + TMR1H << 8   'stuff the contents of the timer register into a word
    Gosub Fingercheck
    
    TMR1L = 0     'reset counter to 0...
    TMR1H = 0     'upper 1/2 too
    TMR2 = 0       'rest timer 2
    PIR1.1 = 0   'Clear TMR2 Interrupt Flag
    T1CON.0 = 1  'restart timer1
    T2CON.2 = 1  'restart timer2
@ INT_RETURN
    enable 
    
'----Average the timercount result----------------------------------------------

Fingercheck:
    timerave = timerave - (timerave/AvgCount)    'average the count so you have a reference to compare....
    timerave = timerave + (timercount/AvgCount)  '...with yimercount
        
    If timerave - (timerave /40) > timercount then  'If timercount drops more than 2.5% below the average, signal that a button is pressed.
        low LED      'make the LED do a little dance.
        pause 50
        High LED
        pause 25
    endif
    
    If timercount > timerave +50 then    'do a "fast recovery" on the average when finger is removed.
       timerave = timercount
    endif
    return     
    
'----Main loop-----------------------------------------------------------
Main:
    LCDOUT $fe,2, " Count= ", dec timercount,"    ",$fe,$C0,"Average = ", dec timerave,"    "
    pause 50  
GOTO Main

    end

[gmglickman]

Anybody else working with capacitive sensing? Any updates?

[rmteo]

I have used capacitive sensing in a handheld terminal with a graphic LCD. It scans 24 keys (although it will handle up to 32 keys) and does require a special MCU - I'm using a PIC18F44K20. Does auto-repeat, audible feedback, etc.

[Bruce]

Nice looking project rmteo. Do you have a PBP example for it?