From 189dd2dd30dcba26e41f3d9b12dc66cf1c70cf78 Mon Sep 17 00:00:00 2001
From: Theo Arends <11044339+arendst@users.noreply.github.com>
Date: Mon, 23 Feb 2026 16:16:54 +0100
Subject: [PATCH] Add support for Sensirion STCC4 CO2 sensor
- Change SHT1x software reset I2C bus after initial (un)detection
---
CHANGELOG.md | 2 +
CODE_OWNERS.md | 1 +
I2CDEVICES.md | 3 +-
RELEASENOTES.md | 2 +
lib/lib_i2c/Sensirion_i2c_stcc4/.clang-format | 14 +
lib/lib_i2c/Sensirion_i2c_stcc4/CHANGELOG.md | 15 +
lib/lib_i2c/Sensirion_i2c_stcc4/LICENSE | 29 ++
lib/lib_i2c/Sensirion_i2c_stcc4/README.md | 197 +++++++++
.../examples/exampleUsage/exampleUsage.ino | 139 ++++++
.../exampleUsageSingleShot.ino | 165 +++++++
...Arduino-Mega-2560-Rev3-i2c-pinout-3.3V.png | Bin 0 -> 415104 bytes
.../images/Arduino-Micro-i2c-pinout-3.3V.png | Bin 0 -> 329645 bytes
.../images/Arduino-Nano-i2c-pinout-3.3V.png | Bin 0 -> 303452 bytes
.../Arduino-Uno-Rev3-i2c-pinout-3.3V.png | Bin 0 -> 322617 bytes
.../Sensirion_i2c_stcc4/images/STCC4.png | Bin 0 -> 273184 bytes
.../images/STCC4_pinout.png | Bin 0 -> 228152 bytes
.../images/esp32-devkitc-i2c-pinout-3.3V.png | Bin 0 -> 537095 bytes
lib/lib_i2c/Sensirion_i2c_stcc4/keywords.txt | 43 ++
.../Sensirion_i2c_stcc4/library.properties | 11 +
lib/lib_i2c/Sensirion_i2c_stcc4/metadata.yml | 7 +
.../src/SensirionI2cStcc4.cpp | 364 ++++++++++++++++
.../src/SensirionI2cStcc4.h | 402 ++++++++++++++++++
tasmota/my_user_config.h | 3 +-
tasmota/tasmota_support/support_a_i2c.ino | 17 +
tasmota/tasmota_support/support_features.ino | 4 +-
tasmota/tasmota_xsns_sensor/xsns_07_sht1x.ino | 1 +
.../tasmota_xsns_sensor/xsns_119_sen6x.ino | 79 ++--
.../tasmota_xsns_sensor/xsns_120_stcc4.ino | 284 +++++++++++++
tools/decode-status.py | 4 +-
29 files changed, 1748 insertions(+), 38 deletions(-)
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/.clang-format
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/CHANGELOG.md
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/LICENSE
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/README.md
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/examples/exampleUsage/exampleUsage.ino
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/examples/exampleUsageSingleShot/exampleUsageSingleShot.ino
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/Arduino-Mega-2560-Rev3-i2c-pinout-3.3V.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/Arduino-Micro-i2c-pinout-3.3V.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/Arduino-Nano-i2c-pinout-3.3V.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/Arduino-Uno-Rev3-i2c-pinout-3.3V.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/STCC4.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/STCC4_pinout.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/images/esp32-devkitc-i2c-pinout-3.3V.png
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/keywords.txt
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/library.properties
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/metadata.yml
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/src/SensirionI2cStcc4.cpp
create mode 100644 lib/lib_i2c/Sensirion_i2c_stcc4/src/SensirionI2cStcc4.h
create mode 100644 tasmota/tasmota_xsns_sensor/xsns_120_stcc4.ino
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6d852d550..2a456c613 100755
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file.
### Added
- Support for Sensirion SCD43 CO2 sensor
- I2S full duplex, auto rx sample rate (#24469)
+- Support for Sensirion STCC4 CO2 sensor
### Breaking Changed
@@ -15,6 +16,7 @@ All notable changes to this project will be documented in this file.
- Matter improved parameters handling (#24471)
- Sensirion Core library from v0.6.0 to v0.7.2
- Sen5x power on delay of 60ms (#24452)
+- SHT1x software reset I2C bus after initial (un)detection
### Fixed
- Do not free BT memory when in use (#24480)
diff --git a/CODE_OWNERS.md b/CODE_OWNERS.md
index e60ceddf0..9da2da52b 100644
--- a/CODE_OWNERS.md
+++ b/CODE_OWNERS.md
@@ -236,6 +236,7 @@ In addition to @arendst the following code is mainly owned by:
| xsns_117_c8_co2_5k | @jeroenvermeulen
| xsns_118_ags02ma | Akshaylal S
| xsns_119_sen6x | @arendst
+| xsns_120_stcc4 | @arendst
| |
| xsns_127_esp32_sensors | @arendst
| |
diff --git a/I2CDEVICES.md b/I2CDEVICES.md
index 16f7ef408..972ba94ec 100644
--- a/I2CDEVICES.md
+++ b/I2CDEVICES.md
@@ -139,5 +139,6 @@ Index | Define | Driver | Device | Address(es) | Bus2 | Descrip
96 | USE_RX8025 | xdrv_56 | RX8025 | 0x32 | Yes | RX8025 RTC
97 | USE_SEN6X | xsns_119 | SEN6X | 0x6B | Yes | Gas (CO2/VOC/NOx index) and air quality (PPM <1,<2.5,<4,<10)
98 | USE_FM24CXX | xdrv_93 | FM24CXX | 0x50 - 0x57| Yes | FM24CXX - External FRAM with console / berry R/W operations
-
+ 99 | USE_STCC4 | xsns_120 | STCC4 | 0x64, 0x65 | Yes | CO2 and optional temperature and humidity sensor
+
NOTE: Bus2 supported on ESP32 only.
diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 22eabbe12..4477f21d6 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -115,12 +115,14 @@ The latter links can be used for OTA upgrades too like ``OtaUrl https://ota.tasm
## Changelog v15.3.0.1
### Added
- Support for Sensirion SCD42 and SCD43 CO2 sensor
+- Support for Sensirion STCC4 CO2 sensor
- I2S full duplex, auto rx sample rate [#24469](https://github.com/arendst/Tasmota/issues/24469)
- Sen5x power on delay of 60ms [#24452](https://github.com/arendst/Tasmota/issues/24452)
### Changed
- Sensirion Core library from v0.6.0 to v0.7.2
- LVGL library from v9.4.0 to v9.5.0 [#24470](https://github.com/arendst/Tasmota/issues/24470)
+- SHT1x software reset I2C bus after initial (un)detection
- Matter improved parameters handling [#24471](https://github.com/arendst/Tasmota/issues/24471)
### Fixed
diff --git a/lib/lib_i2c/Sensirion_i2c_stcc4/.clang-format b/lib/lib_i2c/Sensirion_i2c_stcc4/.clang-format
new file mode 100644
index 000000000..047f2adf1
--- /dev/null
+++ b/lib/lib_i2c/Sensirion_i2c_stcc4/.clang-format
@@ -0,0 +1,14 @@
+---
+Language: Cpp
+BasedOnStyle: LLVM
+IndentWidth: 4
+AlignAfterOpenBracket: Align
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: false
+IndentCaseLabels: true
+SpacesBeforeTrailingComments: 2
+PointerAlignment: Left
+AlignEscapedNewlines: Left
+ForEachMacros: ['TEST_GROUP', 'TEST']
+...
diff --git a/lib/lib_i2c/Sensirion_i2c_stcc4/CHANGELOG.md b/lib/lib_i2c/Sensirion_i2c_stcc4/CHANGELOG.md
new file mode 100644
index 000000000..e29172443
--- /dev/null
+++ b/lib/lib_i2c/Sensirion_i2c_stcc4/CHANGELOG.md
@@ -0,0 +1,15 @@
+# CHANGELOG
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.0.0] - 2025-6-20
+
+### Added
+
+- Initial support for STCC4.
+
+[Unreleased]: https://github.com/Sensirion/arduino-i2c-stcc4/compare/1.0.0...HEAD
+[1.0.0]: https://github.com/Sensirion/arduino-i2c-stcc4/releases/tag/1.0.0
\ No newline at end of file
diff --git a/lib/lib_i2c/Sensirion_i2c_stcc4/LICENSE b/lib/lib_i2c/Sensirion_i2c_stcc4/LICENSE
new file mode 100644
index 000000000..20627661d
--- /dev/null
+++ b/lib/lib_i2c/Sensirion_i2c_stcc4/LICENSE
@@ -0,0 +1,29 @@
+BSD 3-Clause License
+
+Copyright (c) 2025, Sensirion AG
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+ list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+ this list of conditions and the following disclaimer in the documentation
+ and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+ contributors may be used to endorse or promote products derived from
+ this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/lib/lib_i2c/Sensirion_i2c_stcc4/README.md b/lib/lib_i2c/Sensirion_i2c_stcc4/README.md
new file mode 100644
index 000000000..830577b2d
--- /dev/null
+++ b/lib/lib_i2c/Sensirion_i2c_stcc4/README.md
@@ -0,0 +1,197 @@
+# Sensirion I²C STCC4 Arduino Library
+
+This is the Sensirion STCC4 library for Arduino allowing you to
+communicate with a STCC4 sensor
+over I²C.
+
+
+
+Click [here](https://sensirion.com/products/catalog/STCC4) to learn more about the Sensirion STCC4 sensor.
+
+
+
+The default I²C address of [STCC4](https://sensirion.com/products/catalog/STCC4) is **0x64**.
+
+> [!NOTE]
+> The SEK-STCC4 board from Sensirion includes a STCC4 and a SHT4x for temperature and humidity compensation, which is controlled by the STCC4 through the integrated I2C controller interface. The provided examples are designed considering this sensor configuration.
+
+
+## Installation of the library
+
+This library can be installed using the Arduino Library manager:
+Start the [Arduino IDE](http://www.arduino.cc/en/main/software) and open
+the Library Manager via
+
+`Sketch` ➔ `Include Library` ➔ `Manage Libraries...`
+
+Search for the `Sensirion I2C STCC4` library in the `Filter
+your search...` field and install it by clicking the `install` button.
+
+If you cannot find it in the library manager, download the latest release as .zip file
+and add it to your [Arduino IDE](http://www.arduino.cc/en/main/software) via
+
+`Sketch` ➔ `Include Library` ➔ `Add .ZIP Library...`
+
+Don't forget to **install the dependencies** listed below the same way via library
+manager or `Add .ZIP Library`
+
+#### Dependencies
+* [Sensirion Core](https://github.com/Sensirion/arduino-core)
+
+## Connect the sensor
+
+Use the following pin description to connect your STCC4 to the standard I²C bus of your Arduino board:
+
+
+
+| *Pin* | *Cable Color* | *Name* | *Description* | *Comments* |
+|-------|---------------|:------:|----------------|------------|
+| 1 | black | GND | Ground |
+| 2 | red | VDD | Supply Voltage | 2.7V to 5.5V
+| 3 | green | SDA | I2C: Serial data input / output |
+| 4 | yellow | SCL | I2C: Serial clock input |
+
+
+
+
+The recommended voltage is 3.3V.
+
+### Board specific wiring
+You will find pinout schematics for recommended board models below:
+
+
+
+Arduino Uno
+
+
+| *STCC4* | *STCC4 Pin* | *Cable Color* | *Board Pin* |
+| :---: | --- | --- | --- |
+| GND | 1 | black | GND |
+| VDD | 2 | red | 3.3V |
+| SDA | 3 | green | D18/SDA |
+| SCL | 4 | yellow | D19/SCL |
+
+
+
+
+
+Arduino Nano
+
+
+| *STCC4* | *STCC4 Pin* | *Cable Color* | *Board Pin* |
+| :---: | --- | --- | --- |
+| GND | 1 | black | GND |
+| VDD | 2 | red | 3.3V |
+| SDA | 3 | green | A4 |
+| SCL | 4 | yellow | A5 |
+
+
+
+
+
+Arduino Micro
+
+
+| *STCC4* | *STCC4 Pin* | *Cable Color* | *Board Pin* |
+| :---: | --- | --- | --- |
+| GND | 1 | black | GND |
+| VDD | 2 | red | 3.3V |
+| SDA | 3 | green | D2/SDA |
+| SCL | 4 | yellow | ~D3/SCL |
+
+
+
+
+
+Arduino Mega 2560
+
+
+| *STCC4* | *STCC4 Pin* | *Cable Color* | *Board Pin* |
+| :---: | --- | --- | --- |
+| GND | 1 | black | GND |
+| VDD | 2 | red | 3.3V |
+| SDA | 3 | green | D20/SDA |
+| SCL | 4 | yellow | D21/SCL |
+
+
+
+
+
+ESP32 DevKitC
+
+
+| *STCC4* | *STCC4 Pin* | *Cable Color* | *Board Pin* |
+| :---: | --- | --- | --- |
+| GND | 1 | black | GND |
+| VDD | 2 | red | 3V3 |
+| SDA | 3 | green | GPIO 21 |
+| SCL | 4 | yellow | GPIO 22 |
+
+
+
+
+
+