keybrd/src/RowScanner_SPIShiftRegisters.h

#ifndef ROWSCANNER_SPI_SHIFTREGISTERS_H
#define ROWSCANNER_SPI_SHIFTREGISTERS_H
#include <Arduino.h>
#include <inttypes.h>
#include <SPI.h>
#include <RowScannerInterface.h>
#include <RowPort.h>
#include <ColPort.h>

/* RowScanner_SPIShiftRegisters reads all shift registers in a daisy chain.
The maximum keys per row is 31, because Arduino's largest type is 32 bits and rowEnd consumes the last bit.
//todo delete: Assumes only one row of shift registers is connected (no Slave Select).

For active low:
    10k pull-up resistor are connected to power
    connect controller's MISO pin to shift register's /QH pin
    in sketch, const bool RowScanner_PinsArray::ACTIVE_HIGH = 0;

For active high:
    10k pull-down resistors are grounded
    connect controller's MISO pin to shift register's QH pin
    in sketch, const bool RowScanner_PinsArray::ACTIVE_HIGH = 1;

shift registers 74HC165 Parallel-In-Serial-Out (PISO) are Daisy chained

The maximum keys per row is 31, because Arduino's largest type is 32 bits and rowEnd consumes the last bit.
call begin() from setup()

*/
class RowScanner_SPIShiftRegisters : public RowScannerInterface
{
    private:
        //todo static const bool ACTIVE_HIGH;          //logic level of strobe pin: 0=activeLow, 1=activeHigh
        static const uint8_t SHIFT_LOAD;               //controller's pin number that is connected to shift register's SHIFT_LOAD pin
        const uint8_t STROBE_PIN;               //Arduino pin number connected to this row
        const uint8_t KEY_COUNT;                //number of keys in row
        const uint8_t BYTE_COUNT;               //number of bytes to read from shift registers
    public:
        RowScanner_SPIShiftRegisters(const uint8_t STROBE_PIN, uint8_t KEY_COUNT)
            : STROBE_PIN(STROBE_PIN), KEY_COUNT(KEY_COUNT), BYTE_COUNT(ceil (float(KEY_COUNT)/8)) {}
        virtual read_pins_t scan(read_pins_mask_t& rowEnd);
        void begin();
};
#endif