cargo: rejigger crate type

convert to hybrid crate, with arch-dependent stuff as a ‘bin’ crate,
with the underlying support in ‘lib’.

the reason for this change is to allow for automated unit-testing on
the device-independent bits. to facilitate this, a ‘t’ alias is
provided which will run the unit tests. this target assumes you're on
a linux system, but you can't have everything.

1 files changed, 52 insertions, 0 deletions

diff --git a/src/logger.rs b/src/logger.rs
new file mode 100644
index 0000000..453e268
--- /dev/null
+++ b/src/logger.rs
@@ -0,0 +1,52 @@
+use core::{
+    cell::RefCell,
+    fmt::{write, Arguments},
+};
+
+use cortex_m::interrupt::{self, Mutex};
+
+#[macro_export]
+macro_rules! log {
+    ($($args:tt)+) => {
+        $crate::logger::log_args(core::format_args!($($args)+))
+    }
+}
+
+#[macro_export]
+macro_rules! logln {
+    () => ({ kprint!("\r\n") });
+    ($fmt: literal $(, $($arg: tt)+)?) => {
+        log!(concat!($fmt, "\n") $(, $($arg)+)?)
+    }
+}
+
+static TX: Mutex<RefCell<Option<arch::Writer>>> = Mutex::new(RefCell::new(None));
+
+pub fn init(tx: arch::Writer) {
+    interrupt::free(|cs| {
+        TX.borrow(cs).replace(Some(tx));
+    });
+}
+
+pub fn log_args(args: Arguments) {
+    interrupt::free(|cs| {
+        TX.borrow(cs)
+            .borrow_mut()
+            .as_mut()
+            .map(|tx| write(tx, args));
+    });
+}
+
+/*
+ * Because the logger needs to have a size in order to be allocated
+ * statically, we need to pull in architecture-specific details about
+ * the implementation.
+ *
+ * By putting everything in an `arch` module, we can more easily swap
+ * things out at compile time with feature flags, or a similar
+ * mechanism.
+ */
+mod arch {
+    use stm32f1xx_hal::{pac::USART1, serial::Tx};
+    pub type Writer = Tx<USART1>;
+}