The i2c module requires an io-* feature

Author: dbrgn

Cargo.toml

@@ -65,6 +65,8 @@ stm32l082 = ["stm32l0x2"]
 
 # Features based on the GPIO peripheral version.
 # This determines the pin function mapping of the MCU.
+# Note: The easiest way to pick the proper io-* feature is to apply
+# the matching mcu-* feature for your MCU!
 io-STM32L021 = []
 io-STM32L031 = []
 io-STM32L051 = []
@@ -302,9 +304,13 @@ required-features = ["rt"]
 name = "flash"
 required-features = ["rt","stm32l082"]
 
+[[example]]
+name = "i2c"
+required-features = ["rt","stm32l0x2","io-STM32L071"]
+
 [[example]]
 name = "i2c_dma"
-required-features = ["rt","stm32l0x2"]
+required-features = ["rt","stm32l0x2","io-STM32L071"]
 
 [[example]]
 name = "rng"

src/dma.rs

@@ -28,13 +28,9 @@ use as_slice::AsSlice;
 
 use crate::{
     adc,
-    i2c,
     pac::{
         self,
         dma1::ch::cr,
-        I2C1,
-        I2C2,
-        I2C3,
     },
     rcc::Rcc,
 };
@@ -48,15 +44,11 @@ use crate::pac::USART1;
     feature = "io-STM32L051",
     feature = "io-STM32L071",
 ))]
-use crate::pac::USART2;
-
-#[cfg(any(
-    feature = "io-STM32L021",
-    feature = "io-STM32L031",
-    feature = "io-STM32L051",
-    feature = "io-STM32L071",
-))]
-use crate::serial;
+use crate::{
+    i2c,
+    serial,
+    pac::{I2C1, I2C2, I2C3, USART2},
+};
 
 #[cfg(feature = "stm32l082")]
 use crate::aes;
@@ -563,6 +555,12 @@ impl_target!(
 );
 
 #[cfg(feature = "stm32l0x2")]
+#[cfg(any(
+    feature = "io-STM32L021",
+    feature = "io-STM32L031",
+    feature = "io-STM32L051",
+    feature = "io-STM32L071",
+))]
 impl_target!(
     // I2C1
     i2c::Tx<I2C1>, Channel2, 6;

src/i2c.rs

@@ -15,7 +15,6 @@ use as_slice::{
     AsMutSlice,
 };
 
-use crate::hal::blocking::i2c::{Read, Write, WriteRead};
 
 #[cfg(feature = "stm32l0x2")]
 use crate::dma::{
@@ -32,6 +31,9 @@ use crate::rcc::Rcc;
 use crate::time::Hertz;
 use cast::u8;
 
+// I²C traits
+use crate::hal::blocking::i2c::{Read, Write, WriteRead};
+
 // I/O Imports
 use crate::gpio::{AltMode, OpenDrain, Output};
 #[cfg(feature = "io-STM32L021")]

src/lib.rs

@@ -23,6 +23,12 @@ pub mod exti;
 #[cfg(feature = "stm32l0x2")]
 pub mod flash;
 pub mod gpio;
+#[cfg(any(
+    feature = "io-STM32L021",
+    feature = "io-STM32L031",
+    feature = "io-STM32L051",
+    feature = "io-STM32L071",
+))]
 pub mod i2c;
 pub mod lptim;
 pub mod prelude;

src/prelude.rs

@@ -13,7 +13,6 @@ pub use crate::{
     adc::AdcExt as _,
     delay::DelayExt as _,
     gpio::GpioExt as _,
-    i2c::I2cExt as _,
     pwr::PowerMode as _,
     rcc::RccExt as _,
     spi::SpiExt as _,
@@ -25,6 +24,14 @@ pub use crate::{
     },
 };
 
+#[cfg(any(
+    feature = "io-STM32L021",
+    feature = "io-STM32L031",
+    feature = "io-STM32L051",
+    feature = "io-STM32L071",
+))]
+pub use crate::i2c::I2cExt as _;
+
 #[cfg(any(
     feature = "io-STM32L021",
     feature = "io-STM32L031",