34 lines
846 B
Markdown
34 lines
846 B
Markdown
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---
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title: Counting Direction and Steps
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summary: Decode edges from the A and B channels to recover step count and direction.
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chapter: Reading Encoder Signals
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order: 2
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tags:
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- decoding
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- interrupts
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- firmware
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estimated_minutes: 10
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---
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# Counting Direction and Steps
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Once you can read the A and B channels, the next job is decoding.
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The most common approach is:
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- trigger on an edge
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- read both channels
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- use a lookup table or state machine to update the count
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If your decoder sees illegal state jumps, you are probably dropping edges or reading a noisy signal.
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## Practical notes
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- Start with low shaft speed.
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- Add debounce or filtering only if the hardware needs it.
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- Test forward and reverse explicitly.
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## Checkpoint
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Write firmware that increments a counter when the shaft turns forward and decrements when it turns backward.
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