From 98b2c8a0b93e586a6da497ff69a750ac89fc764b Mon Sep 17 00:00:00 2001
From: jazzpi <jasper@mezzo.de>
Date: Fri, 17 Oct 2025 08:06:53 +0200
Subject: [PATCH] Add some UART output (via ST-Link VCP)

---
 src/main.rs | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 588522d..439ff8a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,8 @@
 #![no_std]
 #![no_main]
 
+use core::fmt::Write;
+
 // pick a panicking behavior
 use panic_halt as _; // you can put a breakpoint on `rust_begin_unwind` to catch panics
                      // use panic_abort as _; // requires nightly
@@ -10,17 +12,24 @@ use panic_halt as _; // you can put a breakpoint on `rust_begin_unwind` to catch
 use cortex_m::peripheral::{syst, Peripherals};
 use cortex_m_rt::entry;
 
+use stm32f3xx_hal::serial::Serial;
 use stm32f3xx_hal::{self as hal, pac, prelude::*};
 
 #[entry]
 fn main() -> ! {
     let cortex_peripherals = Peripherals::take().unwrap();
+    let dp = pac::Peripherals::take().unwrap();
+    let mut rcc = dp.RCC.constrain();
+    let mut flash = dp.FLASH.constrain();
+    let clocks = rcc.cfgr.sysclk(8.MHz()).freeze(&mut flash.acr);
+
+    // The HAL Serial example does this -- but where does Systick come from?
+    // https://github.com/stm32-rs/stm32f3xx-hal/blob/b0cead18208099b94a085fb634d0db4e75ac6e4d/examples/serial_echo_rtic.rs
+    // let mono = Systick::new(systick, 8_000_000);
     let mut systick = cortex_peripherals.SYST;
     systick.set_clock_source(syst::SystClkSource::Core);
     systick.set_reload(8_000_000); // 1s
     systick.clear_current();
-    let dp = pac::Peripherals::take().unwrap();
-    let mut rcc = dp.RCC.constrain();
 
     // PE9: LD3 (red)
     // PE8: LD4 (blue)
@@ -36,6 +45,17 @@ fn main() -> ! {
         .pe10
         .into_push_pull_output(&mut gpioe.moder, &mut gpioe.otyper);
 
+    let mut gpioc = dp.GPIOC.split(&mut rcc.ahb);
+    let pins = (
+        gpioc
+            .pc4
+            .into_af_push_pull(&mut gpioc.moder, &mut gpioc.otyper, &mut gpioc.afrl),
+        gpioc
+            .pc5
+            .into_af_push_pull(&mut gpioc.moder, &mut gpioc.otyper, &mut gpioc.afrl),
+    );
+
+    let mut uart = Serial::new(dp.USART1, pins, 115200.Bd(), clocks, &mut rcc.apb2);
     systick.enable_counter();
     let mut enabled = true;
     loop {
@@ -44,5 +64,6 @@ fn main() -> ! {
         ld3.toggle().unwrap();
         ld4.toggle().unwrap();
         ld5.toggle().unwrap();
+        uart.write_str("Loop\r\n").unwrap();
     }
 }