[dsmr] Batch UART reads to reduce per-loop overhead (#13826)

esphome/components/dsmr/dsmr.cpp

@@ -40,9 +40,7 @@ bool Dsmr::ready_to_request_data_() {
       this->start_requesting_data_();
     }
     if (!this->requesting_data_) {
-      while (this->available()) {
+      this->drain_rx_buffer_();
-        this->read();
-      }
     }
   }
   return this->requesting_data_;
@@ -115,25 +113,42 @@ void Dsmr::stop_requesting_data_() {
     } else {
       ESP_LOGV(TAG, "Stop reading data from P1 port");
     }
-    while (this->available()) {
+    this->drain_rx_buffer_();
-      this->read();
-    }
     this->requesting_data_ = false;
   }
 }
 
+void Dsmr::drain_rx_buffer_() {
+  uint8_t buf[64];
+  int avail;
+  while ((avail = this->available()) > 0) {
+    if (!this->read_array(buf, std::min(static_cast<size_t>(avail), sizeof(buf)))) {
+      break;
+    }
+  }
+}
+
 void Dsmr::reset_telegram_() {
   this->header_found_ = false;
   this->footer_found_ = false;
   this->bytes_read_ = 0;
   this->crypt_bytes_read_ = 0;
   this->crypt_telegram_len_ = 0;
-  this->last_read_time_ = 0;
 }
 
 void Dsmr::receive_telegram_() {
   while (this->available_within_timeout_()) {
-    const char c = this->read();
+    // Read all available bytes in batches to reduce UART call overhead.
+    uint8_t buf[64];
+    int avail = this->available();
+    while (avail > 0) {
+      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+      if (!this->read_array(buf, to_read))
+        return;
+      avail -= to_read;
+
+      for (size_t i = 0; i < to_read; i++) {
+        const char c = static_cast<char>(buf[i]);
 
         // Find a new telegram header, i.e. forward slash.
         if (c == '/') {
@@ -184,10 +199,22 @@ void Dsmr::receive_telegram_() {
         }
       }
     }
+  }
+}
 
 void Dsmr::receive_encrypted_telegram_() {
   while (this->available_within_timeout_()) {
-    const char c = this->read();
+    // Read all available bytes in batches to reduce UART call overhead.
+    uint8_t buf[64];
+    int avail = this->available();
+    while (avail > 0) {
+      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+      if (!this->read_array(buf, to_read))
+        return;
+      avail -= to_read;
+
+      for (size_t i = 0; i < to_read; i++) {
+        const char c = static_cast<char>(buf[i]);
 
         // Find a new telegram start byte.
         if (!this->header_found_) {
@@ -249,6 +276,8 @@ void Dsmr::receive_encrypted_telegram_() {
         return;
       }
     }
+  }
+}
 
 bool Dsmr::parse_telegram() {
   MyData data;

esphome/components/dsmr/dsmr.h

@@ -85,6 +85,7 @@ class Dsmr : public Component, public uart::UARTDevice {
   void receive_telegram_();
   void receive_encrypted_telegram_();
   void reset_telegram_();
+  void drain_rx_buffer_();
 
   /// Wait for UART data to become available within the read timeout.
   ///