123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566 |
- #include "Scanner_ShiftRegsReadStrobed.h"
-
- Scanner_ShiftRegsReadStrobed::Scanner_ShiftRegsReadStrobed(const bool activeState,
- const uint8_t slaveSelect, const uint8_t byte_count)
- : activeState(activeState),
- 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, activeState); //strobe on
-
- //SPI.beginTransaction( SPISettings(5000000, MSBFIRST, SPI_MODE0) ); //control SPI bus, 5 MHz
-
- //photo-transistor at 3.3v needs 20 ms to stabilize
- delayMicroseconds(20); //monitor trackball here
-
- digitalWrite(slaveSelect, HIGH); //shift the data toward a serial output
-
- digitalWrite(strobePin, !activeState); //strobe off to preserv IR LED life
-
- SPI.transfer(&readState, byte_count);
-
- //SPI.endTransaction();
-
- digitalWrite(slaveSelect, LOW); //load parallel inputs to registers
-
- return readState;
- }
|