From dec323e786314b9fc1d3cdddd8c8153ab237e490 Mon Sep 17 00:00:00 2001
From: Nikolai Ryzhkov <me@namezys.com>
Date: Tue, 25 Nov 2025 19:27:35 +0100
Subject: [PATCH] [sht4x] Read and store a serial number of SHT4x sensors
 (#12089)

Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick+github@koston.org>
---
 esphome/components/sht4x/sht4x.cpp | 23 ++++++++++++++++++++++-
 esphome/components/sht4x/sht4x.h   |  2 ++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/esphome/components/sht4x/sht4x.cpp b/esphome/components/sht4x/sht4x.cpp
index 617b19ef3e..9d29746f0b 100644
--- a/esphome/components/sht4x/sht4x.cpp
+++ b/esphome/components/sht4x/sht4x.cpp
@@ -7,6 +7,7 @@ namespace sht4x {
 static const char *const TAG = "sht4x";
 
 static const uint8_t MEASURECOMMANDS[] = {0xFD, 0xF6, 0xE0};
+static const uint8_t SERIAL_NUMBER_COMMAND = 0x89;
 
 void SHT4XComponent::start_heater_() {
   uint8_t cmd[] = {MEASURECOMMANDS[this->heater_command_]};
@@ -17,6 +18,17 @@ void SHT4XComponent::start_heater_() {
   }
 }
 
+void SHT4XComponent::read_serial_number_() {
+  uint16_t buffer[2];
+  if (!this->get_8bit_register(SERIAL_NUMBER_COMMAND, buffer, 2, 1)) {
+    ESP_LOGE(TAG, "Get serial number failed");
+    this->serial_number_ = 0;
+    return;
+  }
+  this->serial_number_ = (uint32_t(buffer[0]) << 16) | (uint32_t(buffer[1]));
+  ESP_LOGD(TAG, "Serial number: %08" PRIx32, this->serial_number_);
+}
+
 void SHT4XComponent::setup() {
   auto err = this->write(nullptr, 0);
   if (err != i2c::ERROR_OK) {
@@ -24,6 +36,8 @@ void SHT4XComponent::setup() {
     return;
   }
 
+  this->read_serial_number_();
+
   if (std::isfinite(this->duty_cycle_) && this->duty_cycle_ > 0.0f) {
     uint32_t heater_interval = static_cast<uint32_t>(static_cast<uint16_t>(this->heater_time_) / this->duty_cycle_);
     ESP_LOGD(TAG, "Heater interval: %" PRIu32, heater_interval);
@@ -54,11 +68,18 @@ void SHT4XComponent::setup() {
 }
 
 void SHT4XComponent::dump_config() {
-  ESP_LOGCONFIG(TAG, "SHT4x:");
+  ESP_LOGCONFIG(TAG,
+                "SHT4x:\n"
+                "  Serial number: %08" PRIx32,
+                this->serial_number_);
+
   LOG_I2C_DEVICE(this);
   if (this->is_failed()) {
     ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
   }
+  if (this->serial_number_ == 0) {
+    ESP_LOGW(TAG, "Get serial number failed");
+  }
 }
 
 void SHT4XComponent::update() {
diff --git a/esphome/components/sht4x/sht4x.h b/esphome/components/sht4x/sht4x.h
index accc7323be..aec0f3d7f8 100644
--- a/esphome/components/sht4x/sht4x.h
+++ b/esphome/components/sht4x/sht4x.h
@@ -36,7 +36,9 @@ class SHT4XComponent : public PollingComponent, public sensirion_common::Sensiri
   float duty_cycle_;
 
   void start_heater_();
+  void read_serial_number_();
   uint8_t heater_command_;
+  uint32_t serial_number_;
 
   sensor::Sensor *temp_sensor_{nullptr};
   sensor::Sensor *humidity_sensor_{nullptr};