In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Zoot wrote:

There are a *lot* of ways to approach this. This is just one way (pseudo code):

[code]



Interrupt 100000 ' 10us ticks

SensorMeasure:
    sensorTmr = sensorTmr + 1 ' used for timekeeping in main loop (non-interrupt code)
    
    IF sensorState = 2 THEN ' taking measurement
       IF SensorPin = 1 ' say if you are measuring a ping pulse
            sensorVal = sensorVal + 1
       ENDIF
    ENDIF

StepperOut:
    motorFrame = motorFrame + 1  ' this and 100 below lets you control speed; I leave that to you

    IF motorFrame > = 100 THEN ' step once per 10 milliseconds (100 * 100us) = 10000us = 10ms
        motorFrame = 0

    IF motor < 128 THEN ' say if 128 = neutral, 255 = full forward; i'm not counting pulses here nor speed here, but you could
       motorIdx = motorIdx - 1
    ELSEIF motor > 128 THEN
       motorIdx = motorIdx + 1
    ENDIF
    
    motorIdx = motorIdx & %11 ' 0-3

    IF motorIdx = 0 THEN   ' move stepper pulse pattern to output pins use your patterns
       MotorPins = %0001
    ELSEIF motorIdx = 1 THEN
       MotorPins = %1000
   ELSEIF motorIdx = 2 THEN
       MotorPins = %0010
   ELSE
       MotorPins = %0100
   ENDIF

   ENDIF ' if motor frame

   RETURNINT ' interrupt over


Main:

 ' now in the main line, you can use the timer and set the state for triggering/reading sensors, and setting motor stuff


Sensor_State_Stuff:

    IF sensorState = 0 THEN ' waiting to read...
        IF sensorTmr >= 200 ' 200 * 10 us = 20ms between reads
            sensorTmr = 0 ' clear the timer
            HIGH SensorPin  ' trigger Ping ultrasonic
            sensorState = 1 ' next state
       ENDIF
    ENDIF

    IF sensorState = 1 THEN ' waiting for high pulse on ping to finish triggering the ultrasonics   
        IF sensorTmr >= 1 THEN ' 10us trigger
            LOW SensorPin ' end pulse
            IF sensorTmr >=2 THEN ' wait for at least 10us low
 
               sensorTmr = 0 ' clear the timer 
               sensorVal = 0 ' clear the last measured value
               INPUT SensorPin ' make pin input
               sensorState = 2    ' next state
            ENDIF
        ENDIF
    ENDIF
   
   IF sensorState = 2 THEN ' measuring
         IF SensorPin = 0 THEN ' wait for pulse to end
             LOW SensorPin ' turn pin off to keep trigger low
             SensorReading = SensorVal ' move count to stable variable
             sensorTmr = 0
             sensorState = 0 ' back to waiting for next measure cycle
    ENDIF


Motor_Stuff:
    IF SensorReading < 20 THEN
       motor = 10 ' turn one direction
    ELSEIF SensorReading > 200 THEN
      motor = 245
    ELSE
      motor = 128 ' stop
    ENDIF

Done:

   GOTO Main
[/code]


The idea here is your main loop keeps moving through and checking the timers or setting parameters for the interrupt. Even if your main loop "lags", it doesn't matter, the motor will continue to pulse, and the last sensor reading is available, etc.

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