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108 lines
4.3 KiB
Markdown
108 lines
4.3 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/rotaryDecoder/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/rotaryDecoder/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/rotaryDecoder/blob/master/LICENSE)
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[](https://github.com/RobTillaart/rotaryDecoder/releases)
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# rotaryDecoder
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Arduino library for a PCF8574 based rotary decoder - supports 4 rotary encoders.
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## Description
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This experimental library uses a PCF8574 to read the pulses of a rotary encoder.
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As a PCF8574 has 8 lines up to 4 decoders can be read over I2C.
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The PCF interrupt line can be used to detect changes in the position of the encoders.
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If less than 4 rotary encoders are connected one should use the lower bit lines as the
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library assumes these are used. Furthermore it is advised to connect the free PCF8574
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pins to GND so you will not get unintended interrupts.
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## Interface
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- **rotaryDecoder(const int8_t address, TwoWire \*wire = Wire);**
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- **bool begin(uint8_t sda, uint8_t scl, uint8_t count = 4)** ESP32 ea initializes the class
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by setting the I2C sda and scl pins.
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count is the number of rotary encoders connected. (Max 4 per PCF8574)
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Returns true if the PCF8574 is on the I2C bus.
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- **bool begin(uint8_t count = 4)** UNO ea. initializes the class.
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count is the number of rotary encoders connected. (Max 4 per PCF8574)
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Returns true if the PCF8574 is on the I2C bus.
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- **bool isConnected()** returns true if the PCF8574 is on the I2C bus.
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## Core functions
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- **void readInitialState()** read the initial state of the 4 rotary encoders.
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Typically called in setup only, or after a sleep e.g. in combination with **setValue()**
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- **bool checkChange()** polling to see if one or more RE have changed, without updating the counters.
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- **void update()** update the internal counters of the RE. These will add +1 or -1 depending on direction.
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- **void updateSingle()** update the internal counters of the RE. This will add +1 +2 or +3
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as it assumes that the rotary encoder only goes into a single direction.
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## Counters
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- **uint32_t getValue(uint8_r re)** returns the RE counter.
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- **void setValue(uint8_r re, uint32_t value = 0)** (re)set the internal counter to value, default 0
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## Debugging
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- **int8_t getLastPosition(uint8_r re)** returns last position.
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## Performance
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As the decoder is based upon a PCF8574, a I2C device, the performance is affected by the
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clock speed of the I2C bus. All four core functions have one call to **\_read8()** which
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is the most expensive part.
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Early tests gave the following indicative times (Arduino UNO) for the **update()**
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function (with no updates it is ~8 us faster). Note that above 500KHz the gain becomes less
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while reliability of signal decreases. (500KHz is about ~3x faster than 100 KHz)
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As 400 KHz is a standard I2C clock speed it is the preferred one.
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| I2C speed | time (us) | delta | %% |
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|:---------:|:---------:|:-----:|:-----:|
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| 100 KHz | 247 | | |
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| 200 KHz | 146 | 99 | 40% |
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| 300 KHz | 110 | 36 | 24% |
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| 400 KHz | 95 | 15 | 14% | preferred max
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| 500 KHz | 84 | 11 | 12% |
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| 600 KHz | 79 | 5 | 6% |
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| 700 KHz | 73 | 6 | 8% |
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At @400KHz it can update 4 rotary encoders in ~100us.
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At a 50% update percentage this implies a max of about
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5000 **update()** calls per second in theory
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**to be tested in practice**
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Note that a high speed drill goes up to 30000 RPM = 500 RPS = 2000 interrupts per second,
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assuming 4 pulses == 360<36>. (not tested)
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## Operational
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See examples..
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## Future
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#### must
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- update documentation
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- picture how to connect e.g 2 RE's which pins to used
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#### should
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- test with a high speed drill like a Dremel-tool.
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#### could
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- invert flag to adjust to RE that give their pulse just the other way around?
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- setInvert(bool); getInvert();
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- per channel / all? |