diff --git a/common/.gitignore b/common/.gitignore
new file mode 100644
index 0000000..eb5a316
--- /dev/null
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diff --git a/common/Cargo.lock b/common/Cargo.lock
new file mode 100644
index 0000000..69ec4ab
--- /dev/null
+++ b/common/Cargo.lock
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diff --git a/common/Cargo.toml b/common/Cargo.toml
new file mode 100644
index 0000000..4df9eac
--- /dev/null
+++ b/common/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "common"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
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+serde = { version = "1.0.203", default-features = false, features = ["derive"] }
+postcard = "1.0.0"
+framed = {path='/home/andy/programming/framed-rs/framed', default-features=false, features = ["use_nightly"]}
diff --git a/common/src/lib.rs b/common/src/lib.rs
new file mode 100644
index 0000000..8c77b73
--- /dev/null
+++ b/common/src/lib.rs
@@ -0,0 +1,38 @@
+//! Data types shared between the northbridge and southbridge for serial communications
+#![no_std]
+
+use nalgebra::Vector3;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize)]
+pub enum Command {
+    /// Forward, clockwise
+    Twist(f32,f32),
+    Stop,
+
+    /// R, G, B brightness
+    SetLed(Vector3<u8>),
+
+    Enable,
+    FeedWatchdog,
+    Disable,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct Response {
+    enabled: bool,
+    sensor_data: Option<SensorData>,
+    uptime_micros: u64,
+}
+
+#[derive(Serialize, Deserialize)]
+pub enum SensorData {
+    /// degrees per second
+    Gyro(Vector3<f32>),
+    /// g
+    Accelerometer(Vector3<f32>),
+    /// mT
+    Magnetometer(Vector3<f32>),
+    /// V
+    BusVoltage(f32),
+}