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78 lines
3.0 KiB
Markdown
78 lines
3.0 KiB
Markdown
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[![Arduino CI](https://github.com/RobTillaart/rotaryDecoder/workflows/Arduino%20CI/badge.svg)](https://github.com/marketplace/actions/arduino_ci)
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[![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/rotaryDecoder/blob/master/LICENSE)
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[![GitHub release](https://img.shields.io/github/release/RobTillaart/rotaryDecoder.svg?maxAge=3600)](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 RE.
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## Description
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Experimental - not tested yet
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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 cnt = 4)** ESP32 ea initializes the class.
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sets I2C pins.
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cnt 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 begin(uint8_t cnt = 4)** UNO ea. initializes the class.
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cnt 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 inital state of the 4 rotary encoders. 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 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 val = 0)** (re)set the internal counter to val, default 0
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## Debugging
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- **int8_t getLastPosition(uint8_r re)**
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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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clockspeed of the I2C bus. 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 (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 ~3x faster than 100 KHz)
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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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