12F683 and DT Instant Interrupts

[mr.sneezy]

I thought I might post my first working cut. It creates an 8ch PPM frame. The first two channels step in opposition to each other. The device allows me to run tests on manufacturers transmitter modules without using a real RC transmitter or operator.

I enhanced it after this for different speeds and button control

'****************************************************************
'*  Name    : 8ch PPM generator.BAS                                                                           
'*  Author  : Martin S (mr.sneezy)                                                                               
'*  Notice  : Copyright (c) 2008 [select VIEW...EDITOR OPTIONS]                                     
'*          : All Rights Reserved                                                                                    
'*  Date    : 22/11/2008                                                                                            
'*  Version : 1.0                                                                                                       
'*  Notes   :   Code for PIC12F683, logic direction suits Futaba compatible TX modules         
'*          :                                                                                                              
'****************************************************************
Define Osc 4

' Software Defines
' ----------------
        Temp_Var2 var word
        Servo_dir var byte      ' Store the servo going left or right direction flag 0 or 1
        Run_flag var byte       'Loop flag for triggering a PPM frame
	PPM1_value  var Word	'variable for the value ch1 servo position pulse
	PPM2_value  var Word	'variable for the value ch2 servo position pulse

        PPM_Out Var GPIO.0     'PPM drive for TX module is on this port pin
        LED1 Var GPIO.1         'Indicator LED is on this port pin


 ' Initialise Processor - check for each PIC type
' --------------------
    VRCON.7 = %0    'Comparator voltage reference OFF
    CMCON0 = %111    'Comparator inputs to OFF, all pins normal I/O
    ANSEL = 0        'Turn off all AD's 
      
' Set GPIO port pins as Input or Output
    TRISIO.0 = 0    'Input(0 = output, 1 = Input)
    TRISIO.1 = 0    '
    TRISIO.2 = 0    '
    TRISIO.3 = 1    '
    TRISIO.5 = 1    '
    TRISIO.6 = 1    '
    
INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _my_handler,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

    T1CON = $1                ; TMR1ON
@ INT_ENABLE  TMR1_INT     ; enable Timer 1 interrupts

    Low LED1
    Low PPM_out
    PPM1_value = 500  'seed the center value of the servos
    PPM2_value = 500  'seed the center value of the servos
    Servo_dir = 0        'Set initial servo direction
    
Main:
    While Run_flag = 0      'loop looking for trigger
        goto Main
    Wend
    
    Gosub Start_pulse   'start of a channel (or sync pulse)
    Gosub Channel_1     'channel 1 PPM period
    Gosub Start_pulse   'start of a channel
    Gosub Channel_2     'channel 2 PPM period
    Gosub Unused_ch     'a complete PPM channel pulse set, servo centered (1500uS)
    Gosub Unused_ch     '
    Gosub Unused_ch     '
    Gosub Unused_ch     '
    Gosub Unused_ch     '
    Gosub Unused_ch     '
    Gosub Start_pulse   'start of sync pulse
    
    If Servo_dir = 0 then  'do math while waiting for interrupt, plenty of time
        PPM1_value = PPM1_value + 5    'count upwards ch1 servo goes clockwise
    Else
        PPM1_value = PPM1_value - 5    'count downwards ch1 servo goes anti-clockwise
    Endif
    
    If PPM1_value = 1000  then    'detect servo limit CW
        Servo_dir = 1
    Endif
    
    If PPM1_value = 0  then     'detect servo limit CCW
        Servo_dir = 0
    Endif
    
    PPM2_value = 1000 - PPM1_value     'Ch2 servo moves opposite direction to servo Ch1
   
    Run_flag = 0               'clear the interrupt handlers trigger flag
  GOTO Main

 
Start_pulse:
    high PPM_out 
    Pauseus 400         'channel start high period
    Low PPM_out 
    return

Unused_ch:
    high PPM_out 
    Pauseus 400         'channel start high period
    Low PPM_out 
    Pauseus 1100         'Unused channel low period
    return
    
Channel_1:
    Pauseus PPM1_value   'just leave channel low for X time
    Pauseus 600          'make up the minimum pulse to 1000uS
    return
         
Channel_2:
    Pauseus PPM2_value   'just leave channel low for X time
    Pauseus 600          'make up the minimum pulse to 1000uS (start pluse + possition + this)
    return     


'---[TMR1 - interrupt handler]--------------------------------------------------
my_handler:
    
    T1CON = %0            'Stop timer 1
    TMR1L = $23           'Load for 22.5mS interrupts  
    TMR1H = $A8
    T1CON = %1            'Start timer1
    TOGGLE LED1

    Run_flag = 1

@ INT_RETURN