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165 lines
6.2 KiB
Markdown
165 lines
6.2 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/rotaryDecoderSwitch/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/rotaryDecoderSwitch/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/rotaryDecoderSwitch/issues)
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[](https://github.com/RobTillaart/rotaryDecoderSwitch/blob/master/LICENSE)
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[](https://github.com/RobTillaart/rotaryDecoderSwitch/releases)
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[](https://registry.platformio.org/libraries/robtillaart/rotaryDecoderSwitch)
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# rotaryDecoderSwitch
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Arduino library for a PCF8574 based rotary decoder - supports 2 rotary encoders with a switch.
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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 2 decoders with a switch 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 or if a switch is pressed.
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If only 1 rotary encoders is 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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Strongly related to https://github.com/RobTillaart/rotaryDecoder
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The interface is kept the same as much as possible.
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```cpp
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// connect up to 2 rotary encoders with a switch to 1 PCF8574.
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//
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// RotaryEncoder PCF8574 UNO REMARKS
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// -----------------------------------------------------------
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// 1 pin A pin 0
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// 1 pin B pin 1
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// 1 switch pin 2 (switch to gnd)
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// pin 3 (reserved)
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// 2 pin A pin 4
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// 2 pin B pin 5
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// 2 switch pin 6 (switch to gnd)
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// pin 7 (reserved)
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//
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// SDA A4
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// SCL A5
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//
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```
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Note the above mapping is sort of compatible to using the rotaryDecoder class and using device 0 and 2 only,
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#### Related
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- https://github.com/RobTillaart/rotaryDecoder
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- https://github.com/RobTillaart/PCF8574
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## Interface
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```cpp
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#include "rotaryDecoderSwitch.h"
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```
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#### Constructor
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- **rotaryDecoderSwitch(const int8_t address, TwoWire \*wire = Wire);** constructor to set the address and optional the Wire bus.
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- **bool begin(uint8_t count = 2)** UNO ea. initializes the class.
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count is the number of rotary encoders connected.
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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 2 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, and the flags if a key is pressed.
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The counters will add +1 or -1 depending on direction.
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Need to be called before **getValue()** or before **getKeyPressed()**.
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Note that **update()** must be called as soon as possible after the interrupt occurs (or as often as possible when polling).
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- **void updateSingle()** update the internal counters of the RE.
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This will add +1 +2 or +3 as it assumes that the rotary encoder only goes into a single direction.
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#### Counters & keypresses
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- **uint32_t getValue(uint8_r re)** returns the RE counter. (re = 0 or 1).
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- **void setValue(uint8_r re, uint32_t val = 0)** (re)set the internal counter to val, default 0
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- **bool isKeyPressed(uint8_t re)** returns true is the switch is pressed of the RE selected (re = 0 or 1).
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Note one needs to call **update()** first!
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## Debugging
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- **int8_t getLastPosition(uint8_r re)** (re = 0 or 1). returns last position.
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- **int8_t getRaw()**
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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.
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All four core functions have one call to **\_read()** which 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. Note that above 500KHz the gain becomes less
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while reliability of signal decreases. (500KHz is ~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 | %% | Notes |
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|:-----------:|:-----------:|:-------:|:-----:|:---------|
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| 100 KHz | 234 | | |
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| 200 KHz | 136 | 98 | 42% |
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| 300 KHz | 100 | 36 | 26% |
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| 400 KHz | 85 | 15 | 15% | preferred max
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| 500 KHz | 78 | 7 | 8% |
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| 600 KHz | 67 | 11 | 14% | (strange outlier)
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| 700 KHz | 63 | 4 | 6% |
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(test results differ slightly from the rotaryEncoder class)
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At @400KHz it can update 2 rotary encoders in less than 90 us.
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At a 50% update percentage this implies a max of about 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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- add schema
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- keep in sync with rotaryDecoder library
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#### Should
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- think of what to do with the two "idle lines"
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#### Could
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#### Wont
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## Support
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If you appreciate my libraries, you can support the development and maintenance.
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Improve the quality of the libraries by providing issues and Pull Requests, or
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donate through PayPal or GitHub sponsors.
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Thank you,
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