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89 lines
3.2 KiB
Markdown
89 lines
3.2 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/I2CKeyPad/blob/master/LICENSE)
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[](https://github.com/RobTillaart/I2CKeyPad/releases)
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# I2CKeyPad
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Arduino libray for 4x4 KeyPad connected to an I2C PCF8574
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## Description
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The I2CKeyPad library implements the reading of a 4x4 keypad by means of a PCF8574.
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Smaller keypads, meaning less columns or rows (4x3) can be read with it too.
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A 5x3 keypad would require modification
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## Connection
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The PCF8574 is connected between the processor and the 4x4 keypad, see the conceptual
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below. It might take some trying to get the correct pins connected.
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```
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PROC PCF8574 KEYPAD
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+--------+ +--------+ +--------+
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| | | 0|----------|R |
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| SDA |--------| 1|----------|O |
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| SCL |--------| 2|----------|W |
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| | | 3|----------|S |
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| | | | | |
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| | | 4|----------|C |
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| | | 5|----------|O |
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| | | 6|----------|L |
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| | | 7|----------|S |
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+--------+ +--------+ +--------+
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```
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## Interface
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**I2CKEYPAD keypad()**
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The constructor does nothing specific.
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**keyPad.begin()**
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First call that needs to be done is **keyPad.begin(address)**. It sets the I2C address of the PCF8574 used.
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For the ESP32 **begin(sda, scl, address)** is provided.
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The return value shows if the PCF8574 with the given address is connected properly.
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**keyPad.getKey()**
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Then the user can use the **keyPad.getKey()** to read values from the keypad.
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The read is done in the following way:
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First it scans all rows at once by setting all rows to input and all columns to output.
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If no row is pressed **I2CKEYPAD_NOKEY** code is returned.
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If a row is pressed the row is determined by checking the read value against valid values.
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If the read value is not valid a **I2CKEYPAD_FAIL** code is returned.
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(e.g. double key pressed)
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Then all columns are scanned at once by setting the columns to input and rows to output.
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The column is determined by checking the read value against valid values.
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If the read value is not valid a **I2CKEYPAD_FAIL** code is returned.
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Given the row and column, a number 0..15 is returned.
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**keyPad.getLastKey()**
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returns the last valid key pressed 0..15 or **I2C_KEYPAD_NOKEY** = 16.
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**keyPad.isPressed()**
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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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**keyPad.isConnected()**
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returns false if the PCF8574 cannot be connected to.
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## Char mapping
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The code does not map the index on a character or digit as that depends on the application.
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It returns 0..15 if one key is pressed, 16 for **I2CKEYPAD_NOKEY** and 17 for **I2CKEYPAD_FAIL**.
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## Operation
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See examples
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