Add no_alloc compatibility

.gitignore

@@ -1,3 +1,4 @@
 .idea/*
 target/*
-Cargo.lock
+Cargo.lock
+.DS_Store

Cargo.toml

@@ -16,6 +16,7 @@ embedded-hal = { version = "0.2.7", features = ["unproven"] }
 bitmaps = { version = "3.1.0", default-features = false }
 cortex-m = { version = "0.7.4", optional = true }
 spin = { version = "0.9.8", optional = true }
+heapless = "0.8.0"
 
 [dev-dependencies]
 mockall = "0.11.0"

src/expander.rs

@@ -89,14 +89,13 @@ use crate::guard::LockFreeGuard;
 #[cfg(feature = "spin")]
 use crate::guard::SpinGuard;
 use crate::pins::Pins;
-use alloc::borrow::ToOwned;
-use alloc::string::{String, ToString};
 use bitmaps::Bitmap;
 use core::cell::RefCell;
 use core::fmt::{Debug, Formatter};
 #[cfg(feature = "cortex-m")]
 use cortex_m::interrupt::Mutex as CsMutex;
 use embedded_hal::blocking::i2c::{Read, SevenBitAddress, Write};
+use heapless::String;
 #[cfg(feature = "spin")]
 use spin::Mutex as SpinMutex;
 
@@ -335,14 +334,12 @@ where
     /// Writes the configuration register of the given bank
     fn write_conf(&mut self, bank: Bank) -> Result<(), <B as Write>::Error> {
         match bank {
-            Bank::Bank0 => self.bus.write(
-                self.address,
-                &[COMMAND_CONF_0, self.configuration_0.as_value().to_owned()],
-            ),
-            Bank::Bank1 => self.bus.write(
-                self.address,
-                &[COMMAND_CONF_1, self.configuration_1.as_value().to_owned()],
-            ),
+            Bank::Bank0 => self
+                .bus
+                .write(self.address, &[COMMAND_CONF_0, self.configuration_0.as_value().clone()]),
+            Bank::Bank1 => self
+                .bus
+                .write(self.address, &[COMMAND_CONF_1, self.configuration_1.as_value().clone()]),
         }
     }
 
@@ -351,24 +348,22 @@ where
         match bank {
             Bank::Bank0 => self
                 .bus
-                .write(self.address, &[COMMAND_OUTPUT_0, self.output_0.as_value().to_owned()]),
+                .write(self.address, &[COMMAND_OUTPUT_0, self.output_0.as_value().clone()]),
             Bank::Bank1 => self
                 .bus
-                .write(self.address, &[COMMAND_OUTPUT_1, self.output_1.as_value().to_owned()]),
+                .write(self.address, &[COMMAND_OUTPUT_1, self.output_1.as_value().clone()]),
         }
     }
 
     /// Writes the polarity register of the given bank
     fn write_polarity(&mut self, bank: Bank) -> Result<(), <B as Write>::Error> {
         match bank {
-            Bank::Bank0 => self.bus.write(
-                self.address,
-                &[COMMAND_POLARITY_0, self.polarity_0.as_value().to_owned()],
-            ),
-            Bank::Bank1 => self.bus.write(
-                self.address,
-                &[COMMAND_POLARITY_1, self.polarity_1.as_value().to_owned()],
-            ),
+            Bank::Bank0 => self
+                .bus
+                .write(self.address, &[COMMAND_POLARITY_0, self.polarity_0.as_value().clone()]),
+            Bank::Bank1 => self
+                .bus
+                .write(self.address, &[COMMAND_POLARITY_1, self.polarity_1.as_value().clone()]),
         }
     }
 }
@@ -391,11 +386,11 @@ impl<B: Read<u8> + Write> Debug for RefreshInputError<B> {
     }
 }
 
-impl<B: Read<u8> + Write> ToString for RefreshInputError<B> {
-    fn to_string(&self) -> String {
+impl<B: Read<u8> + Write> RefreshInputError<B> {
+    pub fn to_string(&self) -> String<10> {
         match self {
-            RefreshInputError::WriteError(_) => "WriteError".to_string(),
-            RefreshInputError::ReadError(_) => "ReadError".to_string(),
+            RefreshInputError::WriteError(_) => String::try_from("WriteError").unwrap(),
+            RefreshInputError::ReadError(_) => String::try_from("ReadError").unwrap(),
         }
     }
 }

src/lib.rs

@@ -25,7 +25,6 @@
 #![cfg_attr(not(test), no_std)]
 #![cfg_attr(feature = "strict", deny(warnings))]
 
-extern crate alloc;
 extern crate embedded_hal;
 
 #[cfg(feature = "example")]

src/tests.rs

@@ -9,7 +9,6 @@ use crate::guard::SpinGuard;
 use crate::mocks::{BusMockBuilder, MockI2CBus, WriteError};
 use crate::pin_refreshable::{RefreshableInputPin, RefreshableOutputPin};
 use crate::pins::Pins;
-use alloc::string::ToString;
 use embedded_hal::digital::v2::{InputPin, IoPin, OutputPin, PinState, StatefulOutputPin, ToggleableOutputPin};
 
 #[test]
@@ -247,7 +246,7 @@ fn test_refresh_input_state_write_error() {
     let mut expander = PCA9539::new(i2c_bus, 0x74);
     let result = expander.refresh_input_state(Bank0);
 
-    assert_eq!("WriteError", result.unwrap_err().to_string());
+    assert_eq!("WriteError", result.unwrap_err().to_string().as_str());
 }
 
 #[test]