[modbus] Batch UART reads to reduce loop overhead

esphome/components/dsmr/dsmr.cpp

@@ -40,7 +40,9 @@ bool Dsmr::ready_to_request_data_() {
       this->start_requesting_data_();
     }
     if (!this->requesting_data_) {
-      this->drain_rx_buffer_();
+      while (this->available()) {
+        this->read();
+      }
     }
   }
   return this->requesting_data_;
@@ -113,18 +115,10 @@ void Dsmr::stop_requesting_data_() {
     } else {
       ESP_LOGV(TAG, "Stop reading data from P1 port");
     }
-    this->drain_rx_buffer_();
-    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;
+    while (this->available()) {
+      this->read();
     }
+    this->requesting_data_ = false;
   }
 }
 
@@ -139,144 +133,120 @@ void Dsmr::reset_telegram_() {
 
 void Dsmr::receive_telegram_() {
   while (this->available_within_timeout_()) {
-    // 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;
+    const char c = this->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 == '/') {
+      ESP_LOGV(TAG, "Header of telegram found");
+      this->reset_telegram_();
+      this->header_found_ = true;
+    }
+    if (!this->header_found_)
+      continue;
 
-        // Find a new telegram header, i.e. forward slash.
-        if (c == '/') {
-          ESP_LOGV(TAG, "Header of telegram found");
-          this->reset_telegram_();
-          this->header_found_ = true;
-        }
-        if (!this->header_found_)
-          continue;
+    // Check for buffer overflow.
+    if (this->bytes_read_ >= this->max_telegram_len_) {
+      this->reset_telegram_();
+      ESP_LOGE(TAG, "Error: telegram larger than buffer (%d bytes)", this->max_telegram_len_);
+      return;
+    }
 
-        // Check for buffer overflow.
-        if (this->bytes_read_ >= this->max_telegram_len_) {
-          this->reset_telegram_();
-          ESP_LOGE(TAG, "Error: telegram larger than buffer (%d bytes)", this->max_telegram_len_);
-          return;
-        }
-
-        // Some v2.2 or v3 meters will send a new value which starts with '('
-        // in a new line, while the value belongs to the previous ObisId. For
-        // proper parsing, remove these new line characters.
-        if (c == '(') {
-          while (true) {
-            auto previous_char = this->telegram_[this->bytes_read_ - 1];
-            if (previous_char == '\n' || previous_char == '\r') {
-              this->bytes_read_--;
-            } else {
-              break;
-            }
-          }
-        }
-
-        // Store the byte in the buffer.
-        this->telegram_[this->bytes_read_] = c;
-        this->bytes_read_++;
-
-        // Check for a footer, i.e. exclamation mark, followed by a hex checksum.
-        if (c == '!') {
-          ESP_LOGV(TAG, "Footer of telegram found");
-          this->footer_found_ = true;
-          continue;
-        }
-        // Check for the end of the hex checksum, i.e. a newline.
-        if (this->footer_found_ && c == '\n') {
-          // Parse the telegram and publish sensor values.
-          this->parse_telegram();
-          this->reset_telegram_();
-          return;
+    // Some v2.2 or v3 meters will send a new value which starts with '('
+    // in a new line, while the value belongs to the previous ObisId. For
+    // proper parsing, remove these new line characters.
+    if (c == '(') {
+      while (true) {
+        auto previous_char = this->telegram_[this->bytes_read_ - 1];
+        if (previous_char == '\n' || previous_char == '\r') {
+          this->bytes_read_--;
+        } else {
+          break;
         }
       }
     }
+
+    // Store the byte in the buffer.
+    this->telegram_[this->bytes_read_] = c;
+    this->bytes_read_++;
+
+    // Check for a footer, i.e. exclamation mark, followed by a hex checksum.
+    if (c == '!') {
+      ESP_LOGV(TAG, "Footer of telegram found");
+      this->footer_found_ = true;
+      continue;
+    }
+    // Check for the end of the hex checksum, i.e. a newline.
+    if (this->footer_found_ && c == '\n') {
+      // Parse the telegram and publish sensor values.
+      this->parse_telegram();
+      this->reset_telegram_();
+      return;
+    }
   }
 }
 
 void Dsmr::receive_encrypted_telegram_() {
   while (this->available_within_timeout_()) {
-    // 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;
+    const char c = this->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_) {
-          if ((uint8_t) c != 0xDB) {
-            continue;
-          }
-          ESP_LOGV(TAG, "Start byte 0xDB of encrypted telegram found");
-          this->reset_telegram_();
-          this->header_found_ = true;
-        }
-
-        // Check for buffer overflow.
-        if (this->crypt_bytes_read_ >= this->max_telegram_len_) {
-          this->reset_telegram_();
-          ESP_LOGE(TAG, "Error: encrypted telegram larger than buffer (%d bytes)", this->max_telegram_len_);
-          return;
-        }
-
-        // Store the byte in the buffer.
-        this->crypt_telegram_[this->crypt_bytes_read_] = c;
-        this->crypt_bytes_read_++;
-
-        // Read the length of the incoming encrypted telegram.
-        if (this->crypt_telegram_len_ == 0 && this->crypt_bytes_read_ > 20) {
-          // Complete header + data bytes
-          this->crypt_telegram_len_ = 13 + (this->crypt_telegram_[11] << 8 | this->crypt_telegram_[12]);
-          ESP_LOGV(TAG, "Encrypted telegram length: %d bytes", this->crypt_telegram_len_);
-        }
-
-        // Check for the end of the encrypted telegram.
-        if (this->crypt_telegram_len_ == 0 || this->crypt_bytes_read_ != this->crypt_telegram_len_) {
-          continue;
-        }
-        ESP_LOGV(TAG, "End of encrypted telegram found");
-
-        // Decrypt the encrypted telegram.
-        GCM<AES128> *gcmaes128{new GCM<AES128>()};
-        gcmaes128->setKey(this->decryption_key_.data(), gcmaes128->keySize());
-        // the iv is 8 bytes of the system title + 4 bytes frame counter
-        // system title is at byte 2 and frame counter at byte 15
-        for (int i = 10; i < 14; i++)
-          this->crypt_telegram_[i] = this->crypt_telegram_[i + 4];
-        constexpr uint16_t iv_size{12};
-        gcmaes128->setIV(&this->crypt_telegram_[2], iv_size);
-        gcmaes128->decrypt(reinterpret_cast<uint8_t *>(this->telegram_),
-                           // the ciphertext start at byte 18
-                           &this->crypt_telegram_[18],
-                           // cipher size
-                           this->crypt_bytes_read_ - 17);
-        delete gcmaes128;  // NOLINT(cppcoreguidelines-owning-memory)
-
-        this->bytes_read_ = strnlen(this->telegram_, this->max_telegram_len_);
-        ESP_LOGV(TAG, "Decrypted telegram size: %d bytes", this->bytes_read_);
-        ESP_LOGVV(TAG, "Decrypted telegram: %s", this->telegram_);
-
-        // Parse the decrypted telegram and publish sensor values.
-        this->parse_telegram();
-        this->reset_telegram_();
-        return;
+    // Find a new telegram start byte.
+    if (!this->header_found_) {
+      if ((uint8_t) c != 0xDB) {
+        continue;
       }
+      ESP_LOGV(TAG, "Start byte 0xDB of encrypted telegram found");
+      this->reset_telegram_();
+      this->header_found_ = true;
     }
+
+    // Check for buffer overflow.
+    if (this->crypt_bytes_read_ >= this->max_telegram_len_) {
+      this->reset_telegram_();
+      ESP_LOGE(TAG, "Error: encrypted telegram larger than buffer (%d bytes)", this->max_telegram_len_);
+      return;
+    }
+
+    // Store the byte in the buffer.
+    this->crypt_telegram_[this->crypt_bytes_read_] = c;
+    this->crypt_bytes_read_++;
+
+    // Read the length of the incoming encrypted telegram.
+    if (this->crypt_telegram_len_ == 0 && this->crypt_bytes_read_ > 20) {
+      // Complete header + data bytes
+      this->crypt_telegram_len_ = 13 + (this->crypt_telegram_[11] << 8 | this->crypt_telegram_[12]);
+      ESP_LOGV(TAG, "Encrypted telegram length: %d bytes", this->crypt_telegram_len_);
+    }
+
+    // Check for the end of the encrypted telegram.
+    if (this->crypt_telegram_len_ == 0 || this->crypt_bytes_read_ != this->crypt_telegram_len_) {
+      continue;
+    }
+    ESP_LOGV(TAG, "End of encrypted telegram found");
+
+    // Decrypt the encrypted telegram.
+    GCM<AES128> *gcmaes128{new GCM<AES128>()};
+    gcmaes128->setKey(this->decryption_key_.data(), gcmaes128->keySize());
+    // the iv is 8 bytes of the system title + 4 bytes frame counter
+    // system title is at byte 2 and frame counter at byte 15
+    for (int i = 10; i < 14; i++)
+      this->crypt_telegram_[i] = this->crypt_telegram_[i + 4];
+    constexpr uint16_t iv_size{12};
+    gcmaes128->setIV(&this->crypt_telegram_[2], iv_size);
+    gcmaes128->decrypt(reinterpret_cast<uint8_t *>(this->telegram_),
+                       // the ciphertext start at byte 18
+                       &this->crypt_telegram_[18],
+                       // cipher size
+                       this->crypt_bytes_read_ - 17);
+    delete gcmaes128;  // NOLINT(cppcoreguidelines-owning-memory)
+
+    this->bytes_read_ = strnlen(this->telegram_, this->max_telegram_len_);
+    ESP_LOGV(TAG, "Decrypted telegram size: %d bytes", this->bytes_read_);
+    ESP_LOGVV(TAG, "Decrypted telegram: %s", this->telegram_);
+
+    // Parse the decrypted telegram and publish sensor values.
+    this->parse_telegram();
+    this->reset_telegram_();
+    return;
   }
 }
 

esphome/components/dsmr/dsmr.h

@@ -85,7 +85,6 @@ 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.
   ///

esphome/components/modbus/modbus.cpp

@@ -19,16 +19,27 @@ void Modbus::setup() {
 void Modbus::loop() {
   const uint32_t now = App.get_loop_component_start_time();
 
-  while (this->available()) {
-    uint8_t byte;
-    this->read_byte(&byte);
-    if (this->parse_modbus_byte_(byte)) {
-      this->last_modbus_byte_ = now;
-    } else {
-      size_t at = this->rx_buffer_.size();
-      if (at > 0) {
-        ESP_LOGV(TAG, "Clearing buffer of %d bytes - parse failed", at);
-        this->rx_buffer_.clear();
+  int avail = this->available();
+  if (avail > 0) {
+    // Read all available bytes in batches to reduce UART call overhead.
+    uint8_t buf[64];
+    while (avail > 0) {
+      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+      if (!this->read_array(buf, to_read)) {
+        break;
+      }
+      avail -= to_read;
+
+      for (size_t i = 0; i < to_read; i++) {
+        if (this->parse_modbus_byte_(buf[i])) {
+          this->last_modbus_byte_ = now;
+        } else {
+          size_t at = this->rx_buffer_.size();
+          if (at > 0) {
+            ESP_LOGV(TAG, "Clearing buffer of %d bytes - parse failed", at);
+            this->rx_buffer_.clear();
+          }
+        }
       }
     }
   }