#include "Scanner_ShiftRegsReadStrobed.h" Scanner_ShiftRegsReadStrobed::Scanner_ShiftRegsReadStrobed(const bool strobeOn, const uint8_t slaveSelect, const uint8_t byte_count) : strobeOn(strobeOn), strobeOff(!strobeOn), slaveSelect(slaveSelect), byte_count(byte_count) { pinMode(slaveSelect, OUTPUT); } /* init() is called once for each row from Row constructor. Configures controller to communicate with shift register matrix. */ void Scanner_ShiftRegsReadStrobed::init(const uint8_t strobePin) { pinMode(strobePin, OUTPUT); } /* begin() should be called once from sketch setup(). Initializes shift register's shift/load pin. */ void Scanner_ShiftRegsReadStrobed::begin() { digitalWrite(slaveSelect, HIGH); //initialize ??only needed for first scan SPI.begin(); //todo move this to constructor or init() } /* scan() strobes the row's strobePin and returns state of the shift register's input pins. strobePin is Arduino pin number connected to this row. Bit patterns are 1 bit per key. Scanner_ShiftRegsReadStrobed class was tested on two sets of 74HC165 shift registers and 74AHC1G126 tri-state buffer chips 74HC165 is not an SPI device. The 74HC165 SH/LD polarity is the inverse of SPI slave-select convention. Most SPI chips will high-Z their MISO pin when their slave select signal is high. To use SPI-like protocol, 74HC*126 will high-Z the MISO pin when the slave select signal is low. SPI.beginTransaction() and SPI.endTransaction() are not needed, but would be needed if trackball uses interrupts. */ read_pins_t Scanner_ShiftRegsReadStrobed::scan(const uint8_t strobePin) { read_pins_t readState = 0; //bits, 1 means key is pressed, 0 means released digitalWrite(strobePin, strobeOn); //strobe on //SPI.beginTransaction( SPISettings(5000000, MSBFIRST, SPI_MODE0) ); //control SPI bus, 5 MHz delayMicroseconds(20); //photo-transistor at 3.3v needs 20 ms to stablize digitalWrite(slaveSelect, HIGH); //shift the data toward a serial output digitalWrite(strobePin, strobeOff); //strobe off SPI.transfer(&readState, byte_count); //SPI.endTransaction(); digitalWrite(slaveSelect, LOW); //load parallel inputs to registers return readState; }