You can find these libraries in the STM32Cube package, which is available for download from the STMicroelectronics website.

Import the required STM HAL libraries for I2C communication.addEventListener(keypadEvent) triggers an event if the keypad is used.Converting an I2C wire library based Arduino code to STM HAL API based code involves a few steps.setDebounceTime(unsigned int time) sets the amount of milliseconds the keypad will wait until it accepts a new keypress/keyEvent.setHoldTime(unsigned int time) sets the amount of milliseconds the user will have to hold a button until the HOLD state is triggered.For example, instead of just testing for a valid key you can test for when a key was pressed. boolean keyStateChanged() let’s you know when the key has changed from one state to another.The four states are IDLE, PRESSED, RELEASED and HOLD. KeyState getState() returns the current state of any of the keys.That means no blinking LED’s, no LCD screen updates, no nothing with the exception of interrupt routines. Warning – It blocks all other code until a key is pressed. char waitForKey() waits forever until someone presses a key.There are many useful functions you can use with the Keypad object. getKey() // Read the key // Print if key pressed if (key) Some useful functions of the Keypad library The pinouts are as follows:Ĭhar key = keypad. When looking at the front of the keypad, the row pins are on the left, and they usually have a dark strip near the connector to help identify them. The keypad has a female Dupont connector. It then searches the keymap array for the character that corresponds to that button. The microcontroller then waits for the switch to be released.If a row pin is LOW, it indicates that the button for that row and column is pressed.Because pull-up resistors are used, the rows will be high unless a button is pressed. The microcontroller then sequentially sets the pin for each column LOW and then checks to see if any of the row pins are LOW.Input pins are pulled HIGH by enabling internal pull-up resistors.Each row is connected to an input pin, and each column is connected to an output pin.Here is how a microcontroller scans rows and columns to identify which button has been pressed. By identifying which column and row are connected, we can determine which button has been pressed.

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