[matrix_keypad] Keep the keys in flash (#20110)

esphome/components/matrix_keypad/__init__.py

@@ -27,6 +27,10 @@ CONF_HAS_PULLDOWNS = "has_pulldowns"
 
 
 def check_keys(obj: ConfigType) -> ConfigType:
+    for ch in obj.get(CONF_KEYS, ""):
+        if not ch.isascii():
+            # Each key is reported as one byte, so only ASCII characters can be key codes
+            raise cv.Invalid(f"Key code {ch!r} is not an ASCII character")
     if CONF_KEYS in obj and len(obj[CONF_KEYS]) != len(obj[CONF_ROWS]) * len(
         obj[CONF_COLUMNS]
     ):
@@ -74,8 +78,11 @@ async def to_code(config: ConfigType) -> None:
         pin = await cg.gpio_pin_expression(conf[CONF_PIN])
         col_pins.append(pin)
     cg.add(var.set_columns(col_pins))
-    if CONF_KEYS in config:
-        cg.add(var.set_keys(config[CONF_KEYS]))
+    if (keys := config.get(CONF_KEYS)) is not None:
+        table = cg.shared_progmem_array(
+            "matrix_keypad_keys", cg.uint8, list(keys.encode())
+        )
+        cg.add(var.set_keys(table))
     cg.add(var.set_debounce_time(config[CONF_DEBOUNCE_TIME]))
     if CONF_HAS_DIODES in config:
         cg.add(var.set_has_diodes(config[CONF_HAS_DIODES]))

esphome/components/matrix_keypad/matrix_keypad.cpp

@@ -58,8 +58,8 @@ void MatrixKeypad::loop() {
       ESP_LOGD(TAG, "key @ row %d, col %d released", row, col);
       for (auto &listener : this->listeners_)
         listener->button_released(row, col);
-      if (this->pressed_key_ < (int) this->keys_.size()) {
-        uint8_t keycode = this->keys_[this->pressed_key_];
+      if (this->keys_ != nullptr) {
+        uint8_t keycode = progmem_read_byte(&this->keys_[this->pressed_key_]);
         ESP_LOGD(TAG, "key '%c' released", keycode);
         for (auto &listener : this->listeners_)
           listener->key_released(keycode);
@@ -81,8 +81,8 @@ void MatrixKeypad::loop() {
   ESP_LOGD(TAG, "key @ row %d, col %d pressed", row, col);
   for (auto &listener : this->listeners_)
     listener->button_pressed(row, col);
-  if (key < (int) this->keys_.size()) {
-    uint8_t keycode = this->keys_[key];
+  if (this->keys_ != nullptr) {
+    uint8_t keycode = progmem_read_byte(&this->keys_[key]);
     ESP_LOGD(TAG, "key '%c' pressed", keycode);
     for (auto &trigger : this->key_triggers_)
       trigger->trigger(keycode);

esphome/components/matrix_keypad/matrix_keypad.h

@@ -27,7 +27,8 @@ class MatrixKeypad final : public key_provider::KeyProvider, public Component {
   void dump_config() override;
   void set_columns(std::vector<GPIOPin *> pins) { columns_ = std::move(pins); };
   void set_rows(std::vector<GPIOPin *> pins) { rows_ = std::move(pins); };
-  void set_keys(std::string keys) { keys_ = std::move(keys); };
+  /// `keys` is a codegen PROGMEM table with one key code per button.
+  void set_keys(const uint8_t *keys) { this->keys_ = keys; }
   void set_debounce_time(uint32_t debounce_time) { debounce_time_ = debounce_time; };
   void set_has_diodes(bool has_diodes) { has_diodes_ = has_diodes; };
   void set_has_pulldowns(bool has_pulldowns) { has_pulldowns_ = has_pulldowns; };
@@ -38,7 +39,7 @@ class MatrixKeypad final : public key_provider::KeyProvider, public Component {
  protected:
   std::vector<GPIOPin *> rows_;
   std::vector<GPIOPin *> columns_;
-  std::string keys_;
+  const uint8_t *keys_{nullptr};
   uint32_t debounce_time_ = 0;
   bool has_diodes_{false};
   bool has_pulldowns_{false};

tests/component_tests/matrix_keypad/config/keys.yaml

@@ -0,0 +1,23 @@
+esphome:
+  name: test
+
+esp8266:
+  board: esp01_1m
+
+matrix_keypad:
+  - id: keypad_a
+    rows:
+      - pin: 12
+      - pin: 13
+    columns:
+      - pin: 14
+      - pin: 15
+    keys: "1234"
+  - id: keypad_b
+    rows:
+      - pin: 4
+      - pin: 5
+    columns:
+      - pin: 0
+      - pin: 2
+    keys: "1234"

tests/component_tests/matrix_keypad/test_keys.py

@@ -0,0 +1,27 @@
+"""Matrix keypad key codes live in a shared PROGMEM table instead of a std::string."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+from esphome.components.matrix_keypad import check_keys
+import esphome.config_validation as cv
+
+
+def test_keys_use_shared_progmem_table(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    main_cpp = generate_main(component_config_path("keys.yaml"))
+
+    assert (
+        "static constexpr uint8_t matrix_keypad_keys[] PROGMEM = {49, 50, 51, 52};"
+        in main_cpp
+    )
+    assert main_cpp.count("->set_keys(matrix_keypad_keys);") == 2
+
+
+def test_non_ascii_keys_are_rejected() -> None:
+    with pytest.raises(cv.Invalid, match="'é' is not an ASCII"):
+        check_keys({"keys": "1é34"})