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