diff --git a/lcd-writer/src/lcd.rs b/lcd-writer/src/lcd.rs
new file mode 100644
index 0000000..10b2a88
--- /dev/null
+++ b/lcd-writer/src/lcd.rs
@@ -0,0 +1,81 @@
+use rppal::{i2c, i2c::I2c};
+use std::io;
+
+const C0: u8 = 7;
+const A0: u8 = 6;
+
+#[allow(unused)]
+#[repr(u8)]
+enum LcdCommand {
+    Clear = 1,
+    ReturnHome = 2,
+    DisplayOn = 1 << 3 | 1 << 2 | 1 << 1 | 1 << 0,
+    FunctionSet = 1 << 5 | 1 << 4 | 1 << 3,
+    EntryModeSet = 1 << 2 | 1 << 1,
+}
+
+#[allow(unused)]
+#[repr(u8)]
+enum ControlByte {
+    Normal = 1 << C0,
+    Last = 0 << C0,
+    Data = 0 << C0 | 1 << A0,
+}
+
+fn i2c_err_to_io_err(err: i2c::Error) -> io::Error {
+    match err {
+        i2c::Error::Io(v) => v,
+        i2c::Error::InvalidSlaveAddress(addr) => io::Error::new(
+            io::ErrorKind::ConnectionRefused,
+            format!("invalid slave address {}", addr),
+        ),
+        i2c::Error::FeatureNotSupported => io::Error::new(
+            io::ErrorKind::ConnectionRefused,
+            "invalid slave address {}".to_owned(),
+        ),
+        i2c::Error::UnknownModel => io::Error::new(
+            io::ErrorKind::ConnectionRefused,
+            "invalid slave address {}".to_owned(),
+        ),
+    }
+}
+
+pub struct Lcd {
+    bus: I2c,
+}
+
+impl Lcd {
+    pub fn new() -> io::Result<Self> {
+        let mut bus = I2c::with_bus(1).map_err(i2c_err_to_io_err)?;
+        bus.set_slave_address(60).map_err(i2c_err_to_io_err)?;
+        let setup = [
+            ControlByte::Last as u8,
+            LcdCommand::FunctionSet as u8,
+            LcdCommand::DisplayOn as u8,
+            LcdCommand::EntryModeSet as u8,
+            LcdCommand::Clear as u8,
+        ];
+        bus.write(&setup).map_err(i2c_err_to_io_err)?;
+        Ok(Self { bus })
+    }
+
+    pub fn write(&mut self, value: &str) -> io::Result<()> {
+        let mut data = vec![ControlByte::Data as u8];
+        data.extend(value.bytes());
+        let _ = self.bus.write(&data).map_err(i2c_err_to_io_err)?;
+        Ok(())
+    }
+
+    pub fn set_cursor(&mut self, col: u8, row: u8) -> io::Result<()> {
+        let pos = col | (row * 0x40) | 1 << 7;
+        let data = vec![ControlByte::Last as u8, pos];
+        let _ = self.bus.write(&data).map_err(i2c_err_to_io_err)?;
+        Ok(())
+    }
+
+    pub fn clear(&mut self) -> io::Result<()> {
+        let data = vec![ControlByte::Last as u8, LcdCommand::Clear as u8];
+        let _ = self.bus.write(&data).map_err(i2c_err_to_io_err)?;
+        Ok(())
+    }
+}
diff --git a/lcd-writer/src/lib.rs b/lcd-writer/src/lib.rs
new file mode 100644
index 0000000..04b1350
--- /dev/null
+++ b/lcd-writer/src/lib.rs
@@ -0,0 +1 @@
+pub mod lcd;
diff --git a/lcd-writer/src/main.rs b/lcd-writer/src/main.rs
index ed5f3fc..99b8f76 100644
--- a/lcd-writer/src/main.rs
+++ b/lcd-writer/src/main.rs
@@ -1,79 +1,21 @@
-use rppal::{i2c, i2c::I2c};
 use std::io::{self, stdin, stdout, BufRead, Write};
 
-const C0: u8 = 7;
-const A0: u8 = 6;
+use lcd::Lcd;
 
-#[allow(unused)]
-#[repr(u8)]
-enum LcdCommand {
-    Clear = 1,
-    ReturnHome = 2,
-    DisplayOn = 1 << 3 | 1 << 2 | 1 << 1 | 1 << 0,
-    FunctionSet = 1 << 5 | 1 << 4 | 1 << 3,
-    EntryModeSet = 1 << 2 | 1 << 1,
-}
-
-#[allow(unused)]
-#[repr(u8)]
-enum ControlByte {
-    Normal = 1 << C0,
-    Last = 0 << C0,
-    Data = 0 << C0 | 1 << A0,
-}
-
-struct Lcd {
-    bus: I2c,
-}
-
-impl Lcd {
-    pub fn new() -> Result<Self, i2c::Error> {
-        let mut bus = I2c::with_bus(1)?;
-        bus.set_slave_address(60)?;
-        let setup = [
-            ControlByte::Last as u8,
-            LcdCommand::FunctionSet as u8,
-            LcdCommand::DisplayOn as u8,
-            LcdCommand::EntryModeSet as u8,
-            LcdCommand::Clear as u8,
-        ];
-        bus.write(&setup)?;
-        Ok(Self { bus })
-    }
-
-    pub fn write(&mut self, value: &str) -> Result<(), i2c::Error> {
-        let mut data = vec![ControlByte::Data as u8];
-        data.extend(value.bytes());
-        let _ = self.bus.write(&data)?;
-        Ok(())
-    }
-
-    pub fn set_cursor(&mut self, col: u8, row: u8) -> Result<(), i2c::Error> {
-        let pos = col | (row * 0x40) | 1 << 7;
-        let data = vec![ControlByte::Last as u8, pos];
-        let _ = self.bus.write(&data)?;
-        Ok(())
-    }
-
-    pub fn clear(&mut self) -> Result<(), i2c::Error> {
-        let data = vec![ControlByte::Last as u8, LcdCommand::Clear as u8];
-        let _ = self.bus.write(&data)?;
-        Ok(())
-    }
-}
+mod lcd;
 
 fn main() -> io::Result<()> {
-    let mut lcd = Lcd::new().unwrap();
+    let mut lcd = Lcd::new()?;
     loop {
         print!("> ");
         stdout().lock().flush()?;
         let mut line = String::new();
         stdin().lock().read_line(&mut line)?;
         if line.starts_with("clear") {
-            lcd.clear().unwrap();
-            lcd.set_cursor(0, 0).unwrap();
+            lcd.clear()?;
+            lcd.set_cursor(0, 0)?;
         } else if line.starts_with("print") {
-            lcd.write(&line[6..]).unwrap();
+            lcd.write(&line[6..])?;
         } else {
             println!("unrecognized command \"{line}\"");
         }