Lessons
2012 Microchip Technology Inc. DS41628B-page 65
3.8 LESSON 7: REVERSIBLE VARIABLE SPEED ROTATE
3.8.1 Introduction
This lesson combines all of the previous lessons in using the button to reverse the
direction of rotation when the button is pressed. The speed of rotation is controlled
using the potentiometer.
3.8.2 Hardware Effects
LEDs will rotate at a speed that is proportional to the ADC value. The switch will toggle
the direction of the LEDs.
3.8.3 Summary
The program needs to keep track of rotation direction and new code needs to be added
to rotate in the other direction. Lesson 5 rotates right and checks for a ‘1’ in the carry
bit to determine when to restart the sequence. In Lesson 7, the program needs to rotate
both ways and check for a ‘1’ in bit 4 of the display when rotating to the left. When the
‘1’ shows up in bit 4 of LATC, it will be re-inserted into bit 0.
FIGURE 3-6: PROGRAM FLOW FOR LESSON 7
Get ADC Measurement
Delay Using ADC Result
Delay 5ms
Is Switch Still Down?
Check if ADC Result is ‘0’
Is Switch Down?
Change Direction
YES
YES
NO
Main Init
Was It Held Down Previously?
Rotate LEDs to Left
Rotate LEDs to Right
Left Direction
YES NO
YES
NO
NO
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