16F726 Capacitive sensing module

[Byte_Butcher]

Well here I am... stuck again.

I'm trying to learn how to use the capacitive sensing module on the 16F726.

My first problem seems to be getting the sensing oscillator running.

I've been through the CSM section (14.0) of the data sheet and I've read AN1171 (Using the Capacitive Sensing Module on the PIC16F72X)

According to AN1171, once I've set the appropriate registers the oscillator should start up. At this point I would expect to see the oscillator running on my chosen sensor pin... right?

I've got my 'scope on pin 21 (RB0/AN12/CPS0/INT) of the PIC but I don't see anything except a few millivolts of 60 cycle hum. It just looks like a high impedance input with no oscillator running.

Shouldn't this be all it takes to get the CSM oscillator running on CPS0 (pin21) ?

 '****************************************************************

Include "MODEDEFS.BAS"   ' Include Shiftin/out modes

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

OSCCON = $10         'set oscillator to 4 Mhz

TRISA= %11111111     'Set 'em all to inputs
ANSELA= %11111111	 ' Set all pins to analog...

TRISB= %11111111   	 'all input
ANSELB= %11111111    'all analog

TRISC= %00000000     'Set portC all outputs   

CPSCON0 = %10001101  'Cap sense on, high range oscillator
CPSCON1 = %00000001  'Cap sense channel input 0 is selected

Could someone please point me in the right direction?

Thanks!

Steve

[Byte_Butcher]

I'm trying to learn to use the Capacitive Sensing Module (CSM) on the PIC16F727. I've had some minor success getting the CSM set up and running, and with reading the count from TMR1 to an LCD module.

I'm using (trying) Darrel's Instant Interrupts to run an ISR when TMR2 matches PR2, but I clearly don't understand what I'm doing yet...

Here's the part that works so far:
I've got the CSM oscillator running and I can see the triangle wave on pin B0. I've got a wire and "touchpad" connected to it, and when I touch the pad the oscillator slows way down, so that part is working great.


Here's what I'm *trying* to do at this point :

Timer1 is used to count pulses on the cap sensing oscillator. It is set up so that Timer2 controls the gate of Timer1 and starts/stops the Timer1 counter.

Timer2 counts until it matches the value in the PR2 register, then stops Timer1 and triggers an interrupt.

The ISR reads the count in the Timer1 register and stores it in a variable called "timercount", then it resets the registers to 0, resets Timer2 to 0, clears the Timer2 interrupt flag, and restarts the timers.

The main loop is supposed to read the contents of "timercount" and display it on an LCD so I can read the change in timercount when a finger touches the sensing pad.


Here's the problems I'm having (so far):

First, the Interrupt seems to "steal the show" and the program never enters the main loop and displays the data on LCD, UNLESS I put a "goto Main" inside the ISR routine. Then it will display my value on the LCD.

Second, the count in TMR1 seems to be entirely dependent on the length of the "pause" in the main loop. With 100mS pause the timer reads about 15,000 counts, with a 200mS pause it reads about 29,000 counts. What's up with that? The ISR zeros the timers each time through.

I've read sections 11-14 (using the timers and CSM) of the 16F727 datasheet (41341B.pdf) *repeatedly*, as well as AN1103 and AN1171 which explain using the CSM in the 16F727. Hey, I even managed to make Darrels "Blinky light" interrupt example work for me, but alas, I seem unable to pull it all together and make the touch sensor routine work. I figured I'd start by reading the count in TMR1 to an LCD so I can see what's happening..

I've been hammering away at this for quite a while and starting to feel rather lost.

Here's the code I've got so far if someone would *please* be so kind as to take a look and offer advice..

'-------------------------------------------------------------------------------
'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 4

OSCCON = $10         'set oscillator to 4 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   'Read/Write line for the LCD

'-----Allocate Variables
timercount   var    word   ' A place to store the count from TMR1

'-----Set up Interrrupts
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR2_INT,  _CheckCount,   PBP,  yes
     endm    
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@ INT_ENABLE  TMR2_INT     ; enable Timer 2 interrupts



low rw          'LCD Read/Write line low (write)
Pause 200       'Let the LCd wake up
lcdout $fe, 1   'Clear LCD

'----- Timer Setup
T2CON.2 = 1     'TMR2 on
T2CON.0 =1      'adjust prescaler
PR2 = $B4       ' w/prescale=1:1, $B4 sets 125us scan rate.  '= 10110100
PIR1.1 = 0      'Clear the TMR2 interupt flag
PIE1.1 = 1      'Turn TMR2 interrupt enable on
T1CON = %11010101 'clock=CAPOSC, prescale=1:2, 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
PIE1.7 = 1 'Enable Gate Interrupt

Goto main   'Just get it going...

'---[TMR2 - interrupt handler]--------------------------------------------------
    disable   'I think I need to kill the interupts here..?
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
    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
  '  gosub main    'if I don't add this, I never seem to get out of the interrupt and return to the main routine...
@ INT_RETURN
    enable     're-enable interrupts
    
'----Main loop-----------------------------------------------------------
Main:
    LCDOUT $fe,2, " Count= ", dec timercount,"    ",$fe,$C0,"  TMR2 = ", dec timertemp,"    "
    pause 100   'changing the duration of the pause also changes the count on timer1.  Why?
    return    
  
GOTO Main

    end

Thanks very much,

Steve

[Darrel Taylor]

I've never used the touch sensor thingy's, but here's a couple items that will be causing problems.

• You've enabled TMR1GIE (PIE1.7), but there isn't a handler for it.
  Don't think you really need it anyway if TMR2 is handling the gate, and creating an interrupt at the same time.
   
• There is a return in your Main loop. Very Bad!
   

[Byte_Butcher]

Ahhh, thanks Darrel... where would this forum be without you! No problem too large or small.

I don't know what happened with the return inside my main loop... Bad late night cut & paste I guess. Thanks for pointing that out!

About TMR1GIE (PIE1.7)...
I've gone back and re-re-re-read section 12.6 (and figure 12-6) about the timer1 gate and "toggle mode" again, and also the "Timer 2 Time Base Setup" section of AN1171, and a few things are starting to make more sense... and it appears that the interrupt I want to watch is NOT the TMR2 to PR2 match, it's the Timer 1 Gate Event Interrupt , "TMR1GIF"(PIR1.7) . That explains some of the other weird results I've had.

I don't see the "Timer 1 Gate Event Interrupt" listed in the Available Interrupt Sources on your website Darrel. Is there a way for me to add that to the selection so i can use TMR1GIF with "Instant Interrupts"?

Thanks very much for your help! Hopefully I'll be able to get the Touch Sensor thing figured out and be one of the first to post a chunk of working code for it.


Steve

[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!

[visnja30]

Hi,
Is it possible to use A ByteBucher code on PIC16F724.

How to modified a Darrels Taylor file "DT_INTS-14.bas" with his red text on this thread.
When I open his file "DT_INTS-14.bas" ver 1.10 I dont see anywhere where I can put this code:

GetIntInfo macro IflagReg, IflagBit

Found = NO
; nolist
ifdef TMR1GIF ;----{ TMR1 Gate Interrupt }---------------[PIR1, TMR1GIF]---
INT_Source PIR1, TMR1GIF, PIE1, TMR1GIE

and


ASM
#define TMR1GATE_INT PIR1,TMR1GIF ;-- Timer1 Gate Interrupt

Can someone help me to use capacitive sensing on this pic

Best regards