Switch to using rtt for cargo embed, update deps

src/main.rs

@@ -1,12 +1,14 @@
 #![no_std]
-#![no_main]
+#![cfg_attr(not(doc), no_main)]
 
 use core::{
     cell::RefCell,
     fmt::Write,
 };
 
-use panic_halt as _;
+use rtt_target::{rprintln, rtt_init_print};
+use panic_rtt_target as _;
+
 
 use cortex_m_rt::entry;
 
@@ -64,6 +66,9 @@ static COUNT: Mutex<RefCell<i32>> = Mutex::new(RefCell::new(0));
 
 #[entry]
 fn main() -> ! {
+    // Init buffers for debug printing
+    rtt_init_print!();
+
     // Get access to the core peripherals from the cortex-m crate
     let mut core_periph = CorePeripherals::take().unwrap();
 
@@ -170,6 +175,8 @@ fn main() -> ! {
     // Turn the LED on via the OutputPin trait
     led.on().unwrap();
 
+    rprintln!("Finished init, starting main loop");
+
     let mut button_last = false;
     // Microcontroller programs never exit main, so we must loop!
     loop {