Multiples digits when press any key

[joaouzeda]

I was having a problem that when a key was pressed it sent multiple digits, my solution was to put a delay in the _getKey4x4() function, as I put below

uint8_t I2CKeyPad::_getKey4x4()
{
  //  key = row + 4 x col
  uint8_t key = 0;

  //  mask = 4 rows as input pull up, 4 columns as output
  uint8_t rows = _read(0xF0);
  //  check if single line has gone low.
  if (rows == 0xF0)      return I2C_KEYPAD_NOKEY;
  else if (rows == 0xE0) key = 0;
  else if (rows == 0xD0) key = 1;
  else if (rows == 0xB0) key = 2;
  else if (rows == 0x70) key = 3;
  else return I2C_KEYPAD_FAIL;

  //  4 columns as input pull up, 4 rows as output
  uint8_t cols = _read(0x0F);
  //  check if single line has gone low.
  if (cols == 0x0F)      return I2C_KEYPAD_NOKEY;
  else if (cols == 0x0E) key += 0;
  else if (cols == 0x0D) key += 4;
  else if (cols == 0x0B) key += 8;
  else if (cols == 0x07) key += 12;
  else return I2C_KEYPAD_FAIL;

  _lastKey = key;

  usleep(50000);

  return key;   //  0..15
}

(updated syntax highlighting)

[RobTillaart]

Sorry for the long delay, I missed the notifications.

[RobTillaart]

@joaouzeda
I will look into it a.s.a.p as I have missed several issues (all within the same time slot) and this one is imho a low priority.
So it might take several days before it will be continued.

Thanks for reporting anyway, appreciated!

[RobTillaart]

@joaouzeda

I was having a problem that when a key was pressed it sent multiple digits ...

It sounds like a bouncing key, did you get the same digit multiple times?

[RobTillaart]

A generic solution could be a parameter (or internal variable), configurable in the interface of the library.

uint8_t I2CKeyPad::_getKey4x4(int debounceDelay = 0)  // default 0 for backwards compatibility
{
  //  key = row + 4 x col
  uint8_t key = 0;

  //  mask = 4 rows as input pull up, 4 columns as output
  uint8_t rows = _read(0xF0);
  //  check if single line has gone low.
  if (rows == 0xF0)      return I2C_KEYPAD_NOKEY;
  else if (rows == 0xE0) key = 0;
  else if (rows == 0xD0) key = 1;
  else if (rows == 0xB0) key = 2;
  else if (rows == 0x70) key = 3;
  else return I2C_KEYPAD_FAIL;

  //  4 columns as input pull up, 4 rows as output
  uint8_t cols = _read(0x0F);
  //  check if single line has gone low.
  if (cols == 0x0F)      return I2C_KEYPAD_NOKEY;
  else if (cols == 0x0E) key += 0;
  else if (cols == 0x0D) key += 4;
  else if (cols == 0x0B) key += 8;
  else if (cols == 0x07) key += 12;
  else return I2C_KEYPAD_FAIL;

  _lastKey = key;

  if (debounceDelay ) delay(debounceDelay ); //  call only if debounceDelay > 0

  return key;   //  0..15
}

Another option could be to have a static timestamp that checks if the last call was less than e.g. 50 millis ago.
if so it could return the last key or some status code e.g. I2C_KEYPAD_TOO_FAST

[RobTillaart]

mmm, debounce delay need to work for all four supported key layouts.

Solution should be implemented in a higher layer. something like:

uint8_t I2CKeyPad::getKey()
{
  if (millis() - lastCall) < threshold return TOOFAST

  uint8_t _key = 0;
  if (_mode == I2C_KEYPAD_5x3) _key = _getKey5x3();
  else if (_mode == I2C_KEYPAD_6x2) _key =_getKey6x2();
  else if (_mode == I2C_KEYPAD_8x1) _key = _getKey8x1();
  else _key =  _getKey4x4();  //  default.
  return _key;
}

[RobTillaart]

@joaouzeda

Solution implemented in pull request #23

(snippet of new readme.md)

Debouncing threshold

Experimental since version 0.4.1, the library implements a debounce threshold.
If a key bounces, it can trigger multiple interrupts, while the purpose is to act like only one keypress. The debounce threshold prevents reading a key too fast. The default value of the threshold is zero to be backwards compatible. The value is set in microseconds, with a maximum of 65535 ~65 milliseconds, which is about 16 keys per second.

// value in microseconds, max 65535 us

• void setDebounceThreshold(uint16_t value = 0) set the threshold,
  default to zero to reset its value.
• uint16_t getDebounceThreshold() return the set threshold.

If a debounce threshold is set, and getKey() is called too fast,
it will return I2C_KEYPAD_THRESHOLD.

[joaouzeda]

Thank for your answer!