diff --git a/lib/io/src/lib.rs b/lib/io/src/lib.rs
index 927fae6..7040188 100644
--- a/lib/io/src/lib.rs
+++ b/lib/io/src/lib.rs
@@ -2,3 +2,4 @@
 
 pub mod gpio;
 pub mod i2c;
+pub mod spi;
diff --git a/lib/io/src/spi.rs b/lib/io/src/spi.rs
new file mode 100644
index 0000000..479dc78
--- /dev/null
+++ b/lib/io/src/spi.rs
@@ -0,0 +1,22 @@
+/// SPI errors that can occur
+/// From: https://docs.embassy.dev/embassy-stm32/git/stm32f103c8/spi/enum.Error.html
+pub enum SpiError {
+    Framing,
+    Crc,
+    ModeFault,
+    Overrun,
+}
+
+/// A word is either u8 or u16
+pub enum WordSize {
+    U8(u8),
+    U16(u16),
+}
+
+/// SPI trait used to abstract SPI and allow for mocking
+pub trait HypedSpi {
+    /// Read data into `words` from the SPI sensor
+    fn read(&mut self, words: &mut [WordSize]) -> Result<(), SpiError>;
+    /// Write data from `words` to the SPI sensor
+    fn write(&mut self, words: &[WordSize]) -> Result<(), SpiError>;
+}