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123 lines
4.7 KiB
Markdown
123 lines
4.7 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/I2CKeyPad8x8/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/I2CKeyPad8x8/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/I2CKeyPad8x8/blob/master/LICENSE)
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[](https://github.com/RobTillaart/I2CKeyPad8x8/releases)
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# I2CKeyPad8x8
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Arduino library for 8x8 or smaller KeyPad connected to an I2C PCF8575.
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## Description
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EXPERIMENTAL (first tests ==> OK)
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The I2CKeyPad8x8 library implements the reading of a 8x8 keypad by means of a PCF8575.
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Smaller keypads, meaning less columns or rows (e.g. 5x4) can be read with it too.
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Relates to https://github.com/RobTillaart/I2CKeyPad. which is an version using PCF8574.
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## Connection
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The PCF8575 is connected between the processor and the (default) 8x8 keypad.
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See the conceptual schema below.
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```
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PROC PCF8575 KEYPAD
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+--------+ +--------+ +--------+
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| | | 0|----------|R |
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| SDA |--------| .|----------|O |
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| SCL |--------| .|----------|W |
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| | | 7|----------|S |
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| | | .| | |
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| | | .| | |
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| | | 8|----------|C |
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| | | .|----------|O |
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| | | .|----------|L |
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| | | 15|----------|S |
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+--------+ +--------+ +--------+
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```
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## Interface
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- **I2CKeyPad8x8(const uint8_t deviceAddress, TwoWire \*wire = &Wire)**
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The constructor sets the device address and optionally
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allows to selects the I2C bus to use.
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- **bool begin()** The return value shows if the PCF8575 with the given address is connected properly.
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- **bool begin(uint8_t sda, uint8_t scl)** for ESP32.
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The return value shows if the PCF8575 with the given address is connected properly.
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- **bool isConnected()** returns false if the PCF8575 cannot be connected to.
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- **uint8_t getKey()** Returns default 0..63 for regular keys,
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Returns 64 if no key is pressed and 65 in case of an error.
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- **uint8_t getLastKey()** Returns the last **valid** key pressed 0..63. Initially it will return 64 (NOKEY).
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- **bool isPressed()** Returns true if one or more keys of the keyPad is pressed,
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however it is not checked if multiple keys are pressed.
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#### KeyMap functions
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**loadKeyMap()** must be called before **getChar()** and **getLastChar()**!
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- **char getChar()** returns the char corresponding to mapped key pressed.
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- **char getLastChar()** returns the last char pressed.
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- **bool loadKeyMap(char \* keyMap)** keyMap should point to a (global) char array of length 66.
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This array maps index 0..63 on a char and index \[64\] maps to **I2CKeyPad8x8_NOKEY** (typical 'N')
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and index \[65\] maps **I2CKeyPad8x8_FAIL** (typical 'F'). index 66 is the null char.
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**WARNING**
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If there is no key map loaded the user should **NOT** call **getChar()** or
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**getLastChar()** as these would return meaningless bytes.
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Note: a keyMap char array may be longer than 66 characters, but only the first 66 are used.
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The length is **NOT** checked upon loading (as it may contain a NULL char).
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#### Basic working
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After the **keypad.begin()** the sketch calls the **keyPad.getKey()** to read values from the keypad.
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- If no key is pressed **I2CKeyPad8x8_NOKEY** code (16) is returned.
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- If the read value is not valid, e.g. two keys pressed, **I2CKeyPad8x8_FAIL** code (17) is returned.
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- Otherwise a number 0..63 is returned.
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Note NOKEY and FAIL bot have bit 8 set, all valid keys don't.
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This allows fast checking for valid keys.
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Only if a key map is loaded, the user can call **getChar()** and **getLastChar()** to get mapped keys.
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## Interrupts
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The library enables the PCF8575 to generate interrupts on the PCF8575 when a key is pressed.
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This makes checking the keypad far more efficient as one does not need to poll over I2C.
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See examples. (TODO)
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## Operation
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See examples
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## Future
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#### must
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- update documentation
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#### should
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- test extensively
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- basic working (OK)
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- interrupts
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- keymapping
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- performance
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- keep in sync with **I2CKeyPad** as much as possible.
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#### would
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