diff --git a/components/ocs_io/i2c/istore.h b/components/ocs_io/i2c/istore.h
index ec3c9709..720b6963 100644
--- a/components/ocs_io/i2c/istore.h
+++ b/components/ocs_io/i2c/istore.h
@@ -9,6 +9,7 @@
 
 #include "ocs_io/gpio/types.h"
 #include "ocs_io/i2c/itransceiver.h"
+#include "ocs_io/i2c/types.h"
 
 namespace ocs {
 namespace io {
@@ -16,25 +17,6 @@ namespace i2c {
 
 class IStore {
 public:
-    enum class TransferSpeed : uint8_t {
-        //! 100 kbit/s.
-        Default,
-
-        //! 400 kbit/s.
-        Fast,
-    };
-
-    enum class AddressLength : uint8_t {
-        //! 7-bit I2C address.
-        Bit_7,
-
-        //! 10-bit I2C address.
-        Bit_10,
-    };
-
-    //! I2C address.
-    using Address = uint16_t;
-
     //! I2C transceiver to communicate with I2C device.
     using ITransceiverPtr = std::unique_ptr<ITransceiver>;
 
diff --git a/components/ocs_io/i2c/target_esp32/master_store.cpp b/components/ocs_io/i2c/target_esp32/master_store.cpp
index 89dd3062..0dc4f749 100644
--- a/components/ocs_io/i2c/target_esp32/master_store.cpp
+++ b/components/ocs_io/i2c/target_esp32/master_store.cpp
@@ -38,27 +38,25 @@ MasterStore::MasterStore(IStore::Params params) {
     ESP_ERROR_CHECK(i2c_new_master_bus(&config, &handle_));
 }
 
-IStore::ITransceiverPtr MasterStore::add(const char* id,
-                                         IStore::AddressLength len,
-                                         IStore::Address addr,
-                                         IStore::TransferSpeed speed) {
+IStore::ITransceiverPtr
+MasterStore::add(const char* id, AddressLength len, Address addr, TransferSpeed speed) {
     i2c_device_config_t config;
     memset(&config, 0, sizeof(config));
 
 #if SOC_I2C_SUPPORT_10BIT_ADDR
-    if (len == IStore::AddressLength::Bit_10) {
+    if (len == AddressLength::Bit_10) {
         config.dev_addr_length = I2C_ADDR_BIT_LEN_10;
     } else {
         config.dev_addr_length = I2C_ADDR_BIT_LEN_7;
     }
 #else  // !SOC_I2C_SUPPORT_10BIT_ADDR
-    configASSERT(len == IStore::AddressLength::Bit_7);
+    configASSERT(len == AddressLength::Bit_7);
     config.dev_addr_length = I2C_ADDR_BIT_LEN_7;
 #endif // SOC_I2C_SUPPORT_10BIT_ADDR
 
     config.device_address = addr;
 
-    if (speed == IStore::TransferSpeed::Fast) {
+    if (speed == TransferSpeed::Fast) {
         config.scl_speed_hz = 400000;
     } else {
         config.scl_speed_hz = 100000;
diff --git a/components/ocs_io/i2c/types.h b/components/ocs_io/i2c/types.h
new file mode 100644
index 00000000..9d960141
--- /dev/null
+++ b/components/ocs_io/i2c/types.h
@@ -0,0 +1,35 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Tendry Lab
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <cstdint>
+
+namespace ocs {
+namespace io {
+namespace i2c {
+
+enum class TransferSpeed : uint8_t {
+    //! 100 kbit/s.
+    Default,
+
+    //! 400 kbit/s.
+    Fast,
+};
+
+enum class AddressLength : uint8_t {
+    //! 7-bit I2C address.
+    Bit_7,
+
+    //! 10-bit I2C address.
+    Bit_10,
+};
+
+//! I2C address.
+using Address = uint16_t;
+
+} // namespace i2c
+} // namespace io
+} // namespace ocs
diff --git a/components/ocs_sensor/sht4x/sensor_pipeline.cpp b/components/ocs_sensor/sht4x/sensor_pipeline.cpp
index d6462685..561f9a72 100644
--- a/components/ocs_sensor/sht4x/sensor_pipeline.cpp
+++ b/components/ocs_sensor/sht4x/sensor_pipeline.cpp
@@ -22,9 +22,8 @@ SensorPipeline::SensorPipeline(io::i2c::IStore& store,
     storage_ = storage_builder.make(storage_id_.c_str());
     configASSERT(storage_);
 
-    transceiver_ =
-        store.add(transceiver_id_.c_str(), io::i2c::IStore::AddressLength::Bit_7,
-                  params.i2c_addr, io::i2c::IStore::TransferSpeed::Fast);
+    transceiver_ = store.add(transceiver_id_.c_str(), io::i2c::AddressLength::Bit_7,
+                             params.i2c_addr, io::i2c::TransferSpeed::Fast);
     configASSERT(transceiver_);
 
     sensor_.reset(new (std::nothrow) Sensor(*transceiver_, *storage_, id, params.sensor));
diff --git a/projects/sht4x-verifier/main/main.cpp b/projects/sht4x-verifier/main/main.cpp
index cbe1e4f3..36025047 100644
--- a/projects/sht4x-verifier/main/main.cpp
+++ b/projects/sht4x-verifier/main/main.cpp
@@ -32,9 +32,9 @@ extern "C" void app_main(void) {
         }));
     configASSERT(store);
 
-    io::i2c::IStore::ITransceiverPtr bus_transceiver = store->add(
-        "bus", io::i2c::IStore::AddressLength::Bit_7, io::i2c::IStore::bus_fanout_address,
-        io::i2c::IStore::TransferSpeed::Fast);
+    io::i2c::IStore::ITransceiverPtr bus_transceiver =
+        store->add("bus", io::i2c::AddressLength::Bit_7,
+                   io::i2c::IStore::bus_fanout_address, io::i2c::TransferSpeed::Fast);
     configASSERT(bus_transceiver);
 
     auto code = bus_transceiver->send(&io::i2c::IStore::bus_reset_command,
@@ -44,9 +44,8 @@ extern "C" void app_main(void) {
         ocs_logw(log_tag, "failed to reset i2c bus: %s", status::code_to_str(code));
     }
 
-    io::i2c::IStore::ITransceiverPtr sensor_transceiver =
-        store->add("sht4x", io::i2c::IStore::AddressLength::Bit_7, 0x44,
-                   io::i2c::IStore::TransferSpeed::Fast);
+    io::i2c::IStore::ITransceiverPtr sensor_transceiver = store->add(
+        "sht4x", io::i2c::AddressLength::Bit_7, 0x44, io::i2c::TransferSpeed::Fast);
     configASSERT(sensor_transceiver);
 
     std::unique_ptr<storage::StorageBuilder> storage_builder(