44 lines
1.6 KiB
C++
44 lines
1.6 KiB
C++
#ifndef ROWSCANNER_SPI_SHIFTREGISTERS_H
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#define ROWSCANNER_SPI_SHIFTREGISTERS_H
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#include <Arduino.h>
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#include <inttypes.h>
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#include <config_keybrd.h>
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#include <SPI.h>
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#include <RowPort.h>
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#include <ColPort.h>
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/* RowScanner_SPIShiftRegisters reads shift registers.
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shift registers 74HC165 Parallel-In-Serial-Out (PISO)
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in sketch:
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const uint8_t RowScanner_SPIShiftRegisters::SHIFT_LOAD = 10;
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call begin() from setup()
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Upto 4 shift registers can be in a daisy chained.
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The maximum keys per row is 31, because Arduino's largest type is 32 bits and rowEnd consumes the last bit.
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The shift registers are active high:
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10k pull-down resistors are grounded
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connect controller's MISO pin to shift register's QH pin
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The shift register needs 5 wires.
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In addition, each row needs to be connected to a strobe pin from controller.
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The two parts of a split keyboard can be connected by one of:
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* eSATA cable (has 7 wires, good for 2 rows)
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* Ethernet cable (has 8 wires, good for 3 rows)
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*/
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class RowScanner_SPIShiftRegisters
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{
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private:
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static const uint8_t SHIFT_LOAD; //controller's pin number that is connected to shift register's SHIFT_LOAD pin
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const uint8_t STROBE_PIN; //Arduino pin number connected to this row
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const read_pins_mask_t ROW_END; //bitwise, 1 bit marks positioned after last key of row
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const uint8_t BYTE_COUNT; //number of bytes to read from shift registers
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public:
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RowScanner_SPIShiftRegisters(const uint8_t STROBE_PIN, uint8_t KEY_COUNT);
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virtual read_pins_t scan(read_pins_mask_t& rowEnd);
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void begin();
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};
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#endif
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