diff --git a/CHANGELOG.md b/CHANGELOG.md
index d856c81..577040d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,31 @@
 # Changelog
 
-## [3.1.2] - Development
+## [4.0.0] - 2025-02-19
+
+### Changed
+
+- __Breaking__: Do not autoconnect on `SerialHandler` zero-arg instantiation ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- __Breaking__: Deprecate `serial_handler` in favor of `connection` ([`0605386`](https://github.com/fossasia/pslab-python/commit/0605386f74f5929008dd7b8396e6bfe9933c6e92)) (Alexander Bessman)
+- __Breaking__: Move `SerialHandler` to `connection` ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- __Breaking__: Move `detect` to `connection` ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- __Breaking__: Make `check_serial_access_permission` private ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- __Breaking__: Move `ADCBufferMixin` to `instrument.buffer` ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+
+### Added
+
+- Add common `connection` module for different control interfaces ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- Add `WLANHandler` class for controlling the PSLab over WLAN ([`f595d01`](https://github.com/fossasia/pslab-python/commit/f595d01b51b8d3d2e7c6b8c8c1e4a051fcb793df)) (Alexander Bessman)
+- Add `ConnectionHandler` base class for `SerialHandler` and `WLANHandler` ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- Add `connection.autoconnect` function ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+- Add `instrument.buffer` module ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+
+### Removed
+
+- __Breaking__: Remove `SerialHandler.wait_for_data` ([`2ae3f09`](https://github.com/fossasia/pslab-python/commit/2ae3f0968fbaac9b99d7fc037fd82f16660cd6e1)) (Alexander Bessman)
+
+### Fixed
+
+- Fix SPI configuration sending one byte too few ([`bd11b73`](https://github.com/fossasia/pslab-python/commit/bd11b7319af7768a6929ba35d0b5e81b43ee5033)) (Alexander Bessman)
 
 ## [3.1.1] - 2025-01-05
 
@@ -16,5 +41,6 @@
 
 _Changelog added in following release._
 
+[4.0.0]: https://github.com/fossasia/pslab-python/releases/tag/4.0.0
 [3.1.1]: https://github.com/fossasia/pslab-python/releases/tag/3.1.1
 [3.1.0]: https://github.com/fossasia/pslab-python/releases/tag/3.1.0
diff --git a/pslab/__init__.py b/pslab/__init__.py
index 16be371..174ca77 100644
--- a/pslab/__init__.py
+++ b/pslab/__init__.py
@@ -17,4 +17,4 @@
     "ScienceLab",
 )
 
-__version__ = "3.1.2"
+__version__ = "4.0.0"