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有一种输入是数字输入，在现实生活中用的特别多。如果还需要计算的话，一般要加上+-*/，这样就更好了。当然除了0~9，以及四位运算，剩下就是点和等于，这样基本上就把常用的计算都包含在内了。不过，如果16个按键全部用gpio表示，则需要16个gpio，看上去有一点浪费。因此，人们想出了薄膜键盘的方法，也就是矩阵键盘，一般按下去的时候，对应的行和列就会拉低，通过这个办法就可以知道哪个按键被按下去了。

1、8个输出

如果是4*4的薄膜键盘，一般就是4+4=8个输出信号。推广一下，如果是3*4，也就是12个按键的键盘，就是3+4=7个输出信号。

2、准备8个gpio

前面谈到了需要8个gpio，所以只需要找到8个引脚就可以了。不失一般性，不妨找到gpio12~gpio19这8个引脚。

3、连线

矩阵键盘本身没有电源线和地线，这和之前的传感器不太一样。所以，我们需要做的就是就是把esp32对应的引脚和矩阵键盘连接起来即可。一般连接的时候，采用公对母的连线，公口连接键盘，母口连接esp32。

4、开始ai编程

连接好线路之后，就可以准备ai编程了。比如告诉ai，用esp32的8个pin脚连接薄膜键盘，8个引脚是pin12到pin19。没什么大问题的话，ai就可以帮助我们生成的答案。

#include <stdio.h> #include "driver/gpio.h" #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "esp_log.h" #include "esp_rom_sys.h" static const char *TAG = "KEYPAD_SCAN"; // ==================== Configuration ==================== #define ROWS 4 #define COLS 4 // GPIO pins for rows (outputs) const gpio_num_t row_pins[ROWS] = {12, 13, 14, 15}; // GPIO pins for columns (inputs with pull-up) const gpio_num_t col_pins[COLS] = {16, 17, 18, 19}; // Key mapping table (4x4 layout) const char key_map[ROWS][COLS] = { {'1', '2', '3', 'A'}, {'4', '5', '6', 'B'}, {'7', '8', '9', 'C'}, {'*', '0', '#', 'D'} }; // Debounce configuration #define DEBOUNCE_THRESHOLD 3 // Number of consistent reads required #define SCAN_INTERVAL_MS 10 // Scan interval in milliseconds #define STABLE_DELAY_US 50 // Delay for signal stabilization // ======================================================== // Debounce state variables static uint8_t last_stable_state[ROWS][COLS] = {0}; // Last debounced key state (0=pressed, 1=released) static uint8_t debounce_counter[ROWS][COLS] = {0}; // Counter for debounce stability // Key event tracking static char last_reported_key = 0; // Last key that was reported static uint32_t last_key_press_time = 0; // Timestamp of last key press /** * @brief Initialize GPIO pins for matrix keypad * * Row pins: Configured as push-pull outputs, initial state HIGH * Column pins: Configured as inputs with internal pull-up resistors */ void keypad_gpio_init(void) { // Initialize row pins as outputs, default HIGH for (int i = 0; i < ROWS; i++) { gpio_config_t io_conf = { .pin_bit_mask = (1ULL << row_pins[i]), .mode = GPIO_MODE_OUTPUT, .pull_up_en = GPIO_PULLUP_DISABLE, .pull_down_en = GPIO_PULLDOWN_DISABLE, .intr_type = GPIO_INTR_DISABLE, }; gpio_config(&io_conf); gpio_set_level(row_pins[i], 1); // Set initial state HIGH } // Initialize column pins as inputs with internal pull-up for (int i = 0; i < COLS; i++) { gpio_config_t io_conf = { .pin_bit_mask = (1ULL << col_pins[i]), .mode = GPIO_MODE_INPUT, .pull_up_en = GPIO_PULLUP_ENABLE, // Enable internal pull-up .pull_down_en = GPIO_PULLDOWN_DISABLE, .intr_type = GPIO_INTR_DISABLE, }; gpio_config(&io_conf); } ESP_LOGI(TAG, "GPIO initialized: %d rows, %d columns", ROWS, COLS); } /** * @brief Scan the matrix keypad and return the currently pressed key * * Scanning principle: * 1. Drive each row LOW one at a time * 2. Read all column pins * 3. If a column reads LOW, the key at that row/column intersection is pressed * 4. Uses debouncing to filter out mechanical bouncing * * @return char Pressed key character, or 0 if no key is pressed */ char keypad_scan(void) { // Iterate through each row for (int row = 0; row < ROWS; row++) { // Drive current row LOW gpio_set_level(row_pins[row], 0); // Small delay to allow signal to stabilize esp_rom_delay_us(STABLE_DELAY_US); // Read all columns for this row for (int col = 0; col < COLS; col++) { // Read column state (0 = pressed, 1 = released due to pull-up) int current_state = gpio_get_level(col_pins[col]); // Debouncing logic: require multiple consistent reads if (current_state != last_stable_state[row][col]) { // State changed, increment counter debounce_counter[row][col]++; if (debounce_counter[row][col] >= DEBOUNCE_THRESHOLD) { // State is stable, update last stable state last_stable_state[row][col] = current_state; debounce_counter[row][col] = 0; // Log state change for debugging if (current_state == 0) { ESP_LOGD(TAG, "Key %c stabilized (pressed)", key_map[row][col]); } else { ESP_LOGD(TAG, "Key %c stabilized (released)", key_map[row][col]); } } } else { // State consistent, reset counter debounce_counter[row][col] = 0; } // Check if key is pressed (active LOW) if (last_stable_state[row][col] == 0) { // Restore row HIGH before returning gpio_set_level(row_pins[row], 1); return key_map[row][col]; } } // Restore row HIGH before moving to next row gpio_set_level(row_pins[row], 1); } return 0; // No key pressed } /** * @brief Task for continuous keypad scanning with event detection * * This task continuously scans the keypad and reports key press/release events * It only reports when key state changes to avoid spamming the log */ void keypad_scan_task(void *pvParameters) { char current_key; TickType_t last_scan_time = 0; ESP_LOGI(TAG, "Keypad scanning task started"); while (1) { // Scan for currently pressed key current_key = keypad_scan(); // Report events only when state changes if (current_key != last_reported_key) { if (current_key != 0) { // Key pressed event ESP_LOGI(TAG, "Key pressed: %c", current_key); last_key_press_time = xTaskGetTickCount(); } else if (last_reported_key != 0) { // Key released event ESP_LOGI(TAG, "Key released: %c", last_reported_key); } last_reported_key = current_key; } // Maintain consistent scan interval vTaskDelay(pdMS_TO_TICKS(SCAN_INTERVAL_MS)); } } /** * @brief Alternative: Simple blocking scan for single key detection * * This function blocks until a key is pressed and returns it * Useful for menu navigation or PIN entry applications * * @return char The key that was pressed */ char keypad_wait_for_key(void) { char key; while (1) { key = keypad_scan(); if (key != 0) { // Wait for key release to avoid multiple detections while (keypad_scan() != 0) { vTaskDelay(pdMS_TO_TICKS(SCAN_INTERVAL_MS)); } return key; } vTaskDelay(pdMS_TO_TICKS(SCAN_INTERVAL_MS)); } } /** * @brief Get the current key state without event logging * * @return char Currently pressed key, or 0 if none */ char keypad_get_key(void) { return keypad_scan(); } /** * @brief Check if a specific key is currently pressed * * @param key The key character to check * @return true if the key is pressed, false otherwise */ bool keypad_is_key_pressed(char key) { char current_key = keypad_scan(); return (current_key == key); } /** * @brief Reset debounce states (useful after deep sleep) */ void keypad_reset_debounce(void) { for (int i = 0; i < ROWS; i++) { for (int j = 0; j < COLS; j++) { last_stable_state[i][j] = 1; // Default to released state debounce_counter[i][j] = 0; } } last_reported_key = 0; ESP_LOGI(TAG, "Debounce states reset"); } /** * @brief Main application entry point */ void app_main(void) { // Initialize GPIO pins keypad_gpio_init(); // Reset debounce states keypad_reset_debounce(); ESP_LOGI(TAG, "4x4 Matrix Keypad Scanner Started"); ESP_LOGI(TAG, "Scan interval: %d ms, Debounce threshold: %d", SCAN_INTERVAL_MS, DEBOUNCE_THRESHOLD); // Option 1: Continuous scanning with event detection (recommended) xTaskCreate(keypad_scan_task, "keypad_scan", 4096, NULL, 5, NULL); // Option 2: Simple blocking scan (uncomment to use) while (1) { char key = keypad_wait_for_key(); ESP_LOGI(TAG, "User entered: %c", key); // Example: Simple calculator or menu logic switch(key) { case 'A': ESP_LOGI(TAG, "Function A triggered"); break; case 'B': ESP_LOGI(TAG, "Function B triggered"); break; case '#': ESP_LOGI(TAG, "Enter key pressed"); break; case '*': ESP_LOGI(TAG, "Back/Cancel pressed"); break; } } // Main loop can do other tasks while keypad is scanned in background while (1) { // Your main application code here // Key events will be printed by the scanning task vTaskDelay(pdMS_TO_TICKS(1000)); } }

5、验证确认

代码ok之后，就可以编译烧入看一下，确认下是不是我们想要的结果。等到结果ok之后，再回头看看代码的流程，做到心中有数即可。等到真正有需要的时候，再来详细分析也不迟。