In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Matthias09 wrote:

and here the complete code for reading an US Digital 360PPR quad encoder. May it help people the same way I was helped.

at startup, only the index channel interrupt is enabled, the system has to find it's reference point. once the index channel interrupt fires, both encoder channel interrupts will be enabled and the program starts to count the angle. Whenever the encoder bypasses the index channel again, the angle is 'reset' to the default value (90deg), making use of the additional information of having an absolute reference point. 

[code]

DEVICE SX28, OSCHS3, TURBO, STACKX, OPTIONX
FREQ 50_000_000		


 Signal_A1 	PIN RB.0 INPUT 		SCHMITT	'Channel A
 Signal_A2	PIN RB.1 INPUT		SCHMITT	'Channel A too
 Signal_I 	PIN RB.2 INPUT 			'Index Channel
 Signal_B 	PIN RC.0 INPUT 			'Does not create an interrupt, is just read within the interrupt handler 
 angle 		VAR BYTE 			'saves the current angle

 INTERRUPT
 ISR_Start:

 WKPND_B = int_storage


 IF int_storage = %0001 THEN 			'Channel A1 interrupts on rising edge. 

	IF signal_B = 1 THEN 			'count only, if B is high

		angle = angle - 1 		'decrement (or increment?)

	ENDIF

 ELSEIF int_storage = %0010 THEN		'Channel A2 interrupts on falling edge.

	IF signal_B = 1 THEN 			'count only, if B is high

		angle = angle + 1 		'increment (or decrement?) 

	ENDIF

 ELSE						'Index Channel Interrupt (including combinations of Index and the A channels).

	WKEN_B  = %11111000			'enable channel A interrupt ports (actually only has to be done after the first fire (as A is initally disabled). 
						'but to a routine would slow the process, which is not good.
	angle = 90				'reset angle to 90deg

 ENDIF

 ISR_Exit:
 WKPND_B = %00000000 				'clear pending register, ALL bits

 RETURNINT 

 PROGRAM Start
 Start:


 WKPND_B = %00000000 				'clear pending register
 WKED_B  = %00000010  				'rising edge detect on the whole B Byte, except the second port of A channel
 WKEN_B  = %11111011	



 angle = 0	

	DO
	
		if angle = 80 then
			led1 = ison
		endif

		if angle = 100 then
			led1 = isoff	
		endif
	LOOP

 END

[/code]

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