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Diffstat (limited to 'Documentation/input/rotary-encoder.txt')
| -rw-r--r-- | Documentation/input/rotary-encoder.txt | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/input/rotary-encoder.txt b/Documentation/input/rotary-encoder.txt index 943e8f6f2b1..92e68bce13a 100644 --- a/Documentation/input/rotary-encoder.txt +++ b/Documentation/input/rotary-encoder.txt @@ -9,6 +9,9 @@ peripherals with two wires. The outputs are phase-shifted by 90 degrees and by triggering on falling and rising edges, the turn direction can be determined. +Some encoders have both outputs low in stable states, whereas others also have +a stable state with both outputs high (half-period mode). + The phase diagram of these two outputs look like this: _____ _____ _____ @@ -26,6 +29,8 @@ The phase diagram of these two outputs look like this: |<-------->| one step + |<-->| + one step (half-period mode) For more information, please see http://en.wikipedia.org/wiki/Rotary_encoder @@ -34,6 +39,13 @@ For more information, please see 1. Events / state machine ------------------------- +In half-period mode, state a) and c) above are used to determine the +rotational direction based on the last stable state. Events are reported in +states b) and d) given that the new stable state is different from the last +(i.e. the rotation was not reversed half-way). + +Otherwise, the following apply: + a) Rising edge on channel A, channel B in low state This state is used to recognize a clockwise turn @@ -96,6 +108,7 @@ static struct rotary_encoder_platform_data my_rotary_encoder_info = { .gpio_b = GPIO_ROTARY_B, .inverted_a = 0, .inverted_b = 0, + .half_period = false, }; static struct platform_device rotary_encoder_device = { |