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keybrd/src/Scanner_uC.cpp

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#include "Scanner_uC.h"
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/* Scanner_uC functions call Arduino's Digital Pins functions
https://www.arduino.cc/en/Tutorial/DigitalPins
https://www.arduino.cc/en/Reference/PinMode
https://www.arduino.cc/en/Reference/DigitalWrite
https://www.arduino.cc/en/Reference/DigitalRead
https://www.arduino.cc/en/Reference/Constants > Digital Pins modes: INPUT, INPUT_PULLUP, and OUTPUT
*/
/* constructor
*/
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Scanner_uC::Scanner_uC(const uint8_t strobePin,
const uint8_t readPins[], const uint8_t readPinCount)
: strobePin(strobePin), readPins(readPins), readPinCount(readPinCount)
{
uint8_t mode;
//configure row
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pinMode(strobePin, OUTPUT);
if (STROBE_ON == LOW) //if active low
{
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mode = INPUT_PULLUP; //use internal pull-up resistor
}
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else //if active high
{
mode = INPUT; //requires external pull-down resistor
}
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//configure read pins
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for (uint8_t i=0; i < readPinCount; i++)
{
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pinMode(readPins[i], mode);
}
}
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/* scan() strobes the row's strobePin and retuns state of readPins.
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Bitwise variables are 1 bit per key.
*/
read_pins_t Scanner_uC::scan()
{
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read_pins_t readState = 0; //bitwise, 1 means key is pressed, 0 means released
read_pins_t readMask = 1; //bitwise, active bit is 1
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//strobe row on
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digitalWrite(strobePin, STROBE_ON);
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delayMicroseconds(3); //time to stablize voltage
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//read all the read pins
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for (uint8_t i=0; i < readPinCount; i++)
{
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if ( digitalRead(readPins[i]) == STROBE_ON )
{
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readState |= readMask;
}
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readMask <<= 1;
}
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//strobe row off
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digitalWrite(strobePin, STROBE_OFF);
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return readState;
}