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76 lines
2.7 KiB
Markdown
76 lines
2.7 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/FastShiftIn/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/FastShiftIn/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/FastShiftIn/blob/master/LICENSE)
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[](https://github.com/RobTillaart/FastShiftIn/releases)
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# FastShiftIn
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Arduino library for **AVR** optimized shiftIn - e.g. for 74HC165.
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- library for FastShiftOut - https://github.com/RobTillaart/FastShiftOut
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- library for FastShiftInOut - https://github.com/RobTillaart/FastShiftInOut
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## Description
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FastShiftIn is a class that has optimized code (AVR only) to shift in data faster
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than the normal **shiftIn()** function.
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It speeds up the shift using low level ports and masks. These are predetermined
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in the constructor of the FastShiftIn object.
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If not an **ARDUINO_ARCH_AVR** or **ARDUINO_ARCH_MEGAAVR** the class falls back
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to the default shiftIn() implementation.
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## Performance
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The performance of **read()** is substantially faster than the default Arduino
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**shiftIn()**, but not as fast as HW SPI.
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Exact how big the performance gain is can be seen with the example sketch.
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It does a comparison and shows how the class is to be used.
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test 0.2.3 Arduino UNO
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| function | time (us) |
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|:---------------------|----------:|
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| read() | 19.30 |
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| readLSBFIRST() | 19.04 |
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| readMSBFIRST() | 19.04 |
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| reference shiftIn() | 107.82 |
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## Interface
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The interface exists of the following functions:
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- **int read(void)** reads a new value.
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- **int lastRead()** returns last value read.
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- **bool setBitOrder(uint8_t bitOrder)** set LSBFIRST or MSBFIRST. Returns false for other values.
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- **uint8_t getBitOrder(void)** returns LSBFIRST or MSBFIRST
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- **int readLSBFIRST(void)** optimized LSB read().
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- **int readMSBFIRST(void)** optimized MSB read().
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## Notes
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- The optimizations are AVR only for now, other platforms may follow.
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- The 74HC165 needs 0.1uF caps and the data and clock lines may need
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pull up resistors, especially if wires are exceeding 10 cm (4").
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## Operation
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See examples
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## Future
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- esp32 optimization readLSBFIRST readMSBFIRST
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- read8() read16(), read24(), read32()
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- **read(uint8_t \* arr, uint8_t nr)** ??
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- example schema
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