add serial example

examples/serial.rs

@@ -0,0 +1,50 @@
+#![no_std]
+#![no_main]
+
+#[allow(unused)]
+use panic_halt;
+
+use metro_m4 as hal;
+use hal::clock::GenericClockController;
+use hal::delay::Delay;
+use hal::prelude::*;
+use hal::{entry, CorePeripherals, Peripherals};
+use hal::timer::TimerCounter;
+use nb::block;
+use bitbang_hal;
+
+#[entry]
+fn main() -> ! {
+    let mut peripherals = Peripherals::take().unwrap();
+    let core = CorePeripherals::take().unwrap();
+    let mut clocks = GenericClockController::with_external_32kosc(
+        peripherals.GCLK,
+        &mut peripherals.MCLK,
+        &mut peripherals.OSC32KCTRL,
+        &mut peripherals.OSCCTRL,
+        &mut peripherals.NVMCTRL,
+    );
+
+    let gclk0 = clocks.gclk0();
+    let timer_clock = clocks.tc2_tc3(&gclk0).unwrap();
+    let mut timer = TimerCounter::tc3_(
+        &timer_clock, 
+        peripherals.TC3,
+    &mut peripherals.MCLK);
+    timer.start(115200.hz()); 
+
+    let mut pins = hal::Pins::new(peripherals.PORT);
+    let rx = pins.d0.into_pull_up_input(&mut pins.port);
+    let tx = pins.d1.into_push_pull_output(&mut pins.port);
+
+    let mut serial = bitbang_hal::serial::Serial::new(tx, rx, timer);
+
+    let mut delay = Delay::new(core.SYST, &mut clocks);
+
+    loop {
+        for byte in b"Hello, World!" {
+            block!(serial.write(*byte)).unwrap();
+        }
+        delay.delay_ms(1000u16);
+    }
+}