Instant Interrupts - Revisited

[picone]

Thank you for the quick reply.

I'm actually working with an ESC that has 11 bit resolution so that is why I was looking for 0.5us steps. I'm not sure how much difference it will make but I wanted to try it out anyway.

I really appreciate the help!

[cncmachineguy]

Really? Who makes the ESC? On the other hand, I doubt you will notice a difference, but hey go for it!!

[picone]

Really? Who makes the ESC? On the other hand, I doubt you will notice a difference, but hey go for it!!

It is a Castle Creations ESC........when I spoke to one of their engineers they said all of their ESCs have 2048+ speed steps. I know I can get away with the 8 bit resolution of a standard ESC......but as an engineer I need to get the best (i.e. overkill!) solution!

[cncmachineguy]

The part I can't get through my thick head is this, how small of a change can we cause to happen in 20mS to a spinning mass? So if the motor were actually spinning 20,000, then thats 9.75 rpm per bit at 11 bit resolution. On the other hand, getting the extra bit from the PIC may cause less time available to do other things. Mind you I have never looked at PWPS.

[Ioannis]

Hi. I am trying to make this Rotary Encoder work with DT-INTS on a 16F1827 device.

It gets once in the interrupt routine and never seem to exit.

Here is the code so far driving me crazy.

ASM
  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_ON & _CP_ON & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
  __config _CONFIG2, _WRT_OFF & _PLLEN_ON & _LVP_OFF & _STVREN_OFF & _BORV_25
ENDASM

DEFINE OSC 32

OSCCON= %11110000   'PLL enabled, Internal RC-8MHz
 
' Set LCD Data port
DEFINE LCD_DREG PORTA
' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_DBIT 0
' Set LCD Register Select port
DEFINE LCD_RSREG PORTA
' Set LCD Register Select bit
DEFINE LCD_RSBIT 4
' Set LCD Enable port
DEFINE LCD_EREG PORTB
' Set LCD Enable bit
DEFINE LCD_EBIT 3
' Set LCD bus size (4 or 8 bits)
DEFINE LCD_BITS 4
' Set number of lines on LCD
DEFINE LCD_LINES 2
' Set command delay time in us
DEFINE LCD_COMMANDUS 1500
' Set data delay time in us
DEFINE LCD_DATAUS 44

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

'Initializing Registers
  PORTB = 0:PORTA = 0
  TRISB = $33
  TRISA = 0
  
  ADCON0 = 0
  ADCON1 = 0
  ANSELA = 0
  ANSELB = 0

  INTCON = $88 ' Binary 10001000
  
  IOCBP=$30
  IOCBN=$30
  
  OPTION_REG = 0
  
  WPUB=$33
  
eeprom 0,[2,0,3,1,1,3,0,2]
led       var portb.4   
Flag      var bit
wsave     VAR BYTE    $70     SYSTEM  ' alternate save location for W 
Q_New     var Byte
Q_Old     var byte
M_Count   var byte [4]
P_Count   var byte [4]
Q_Count   var word
temp      var byte

clear
     
For Q_Old = 0 to 3
Read Q_Old,M_Count[Q_Old]
Read Q_Old + 4,P_Count[Q_Old]
Next Q_Old
     
  Q_Count = 0   
    Q_New = 0
    Q_Old = 0
     Flag = 0  
      
ASM
INT_LIST  macro    ; IntSource,        Label,  Type,  Resetflag?                
        INT_Handler    IOC_INT,      _Encoder,  pbp,     yes       
    endm
    INT_CREATE                   ; Creates the interrupt processor
ENDASM
@ INT_ENABLE IOC_INT            ; enable external (INT) interrupts

'---------------------------- Initialize LCD ----------------------------

Lcdout $fe, 1                               ' Clear LCD screen
Lcdout "System Ready"                       ' Display message
Pause 500                                   ' Wait .5 second
Q_Count=50

Goto Main_Loop

Encoder:                                    ' ISR 
    Q_New = PortB.5 + PortB.5 + PortB.4         ' get port status 
    
    If M_Count[Q_Old] = Q_New then              ' if M_Count code satisfied then minus
              temp=temp+1
              if temp=4 then
                temp=0
                Q_Count = Q_Count - 1
                Flag = 1                       ' set flag to true to update display
              endif
    goto Q_Skip
    endif
    
    If P_Count[Q_Old] = Q_New then              ' if M_Count code satisfied then plus
              temp=temp+1
              if temp=4 then
                temp=0
                Q_Count = Q_Count + 1
                Flag = 1
              endif                       ' set flag to true to update display
    endif
    
Q_Skip:
    Q_Old = Q_New
    toggle portb.6                               ' update Q_Old Byte
@ INT_RETURN


Main_Loop:   
if Flag = 1 then
    Lcdout $fe, 1                              ' Clear LCD screen
    Lcdout dec Q_Count                         ' Display encoder position (counts)
    Flag = 0                                   ' reset flag to false, display updated
endif

pause 100

goto Main_Loop

Thanks,
Ioannis

[Darrel Taylor]

Ioannis,

On those chips, the IOCIF bit is read-only and only gets cleared when ALL of the IOCBF flags are clear.
So you can set the INT_Handler's ResetFlag option to NO.

Then be sure the IOCBF flags are cleared before exiting the ISR.
Also, take a look at section 13.4 in the datasheet regarding clearing the flags.

[Ioannis]

Excellent! Works terrific now.

These chips are a little pain in setting them.

Thanks Darrel.

Ioannis