From 29e343b9c20a85c84aee89be14d32ee559f324a6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rn-Michael?=
 <40151420+ldericher@users.noreply.github.com>
Date: Fri, 15 Mar 2024 12:37:55 +0000
Subject: [PATCH] lock-free reading

---
 bluepill-rs/src/main.rs | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/bluepill-rs/src/main.rs b/bluepill-rs/src/main.rs
index e97ac21..874f987 100644
--- a/bluepill-rs/src/main.rs
+++ b/bluepill-rs/src/main.rs
@@ -20,12 +20,13 @@ mod app {
 
     #[shared]
     struct Shared {
-        buffer: Option<&'static mut [u8; 512]>,
+        buffer: &'static mut [u8; 512],
     }
 
     #[local]
     struct Local {
         tx: Option<dma::TxDma<serial::Tx<pac::USART1>, dma::dma1::C4>>,
+        txbuffer: Option<&'static mut [u8; 512]>,
         delay_us: timer::DelayUs<pac::TIM2>,
         led: gpio::gpioc::PC13<gpio::Output>,
     }
@@ -71,10 +72,11 @@ mod app {
 
         (
             Shared {
-                buffer: Some(singleton!(: [u8; 512] = [0b01010101; 512]).unwrap()),
+                buffer: singleton!(: [u8; 512] = [0b01010101; 512]).unwrap(),
             },
             Local {
                 tx: Some(serial.tx.with_dma(dma1.4)),
+                txbuffer: Some(singleton!(: [u8; 512] = [0; 512]).unwrap()),
 
                 // Configure timer
                 delay_us: cx.device.TIM2.delay_us(&clocks),
@@ -87,25 +89,24 @@ mod app {
         )
     }
 
-    #[idle(local = [tx, delay_us, led], shared = [buffer])]
-    fn idle(mut cx: idle::Context) -> ! {
-        let mut tx = cx.local.tx.take().unwrap();
-
+    #[idle(local = [tx, txbuffer, delay_us, led], shared = [&buffer])]
+    fn idle(cx: idle::Context) -> ! {
         loop {
-            tx = (cx.shared.buffer).lock(|buffer| {
-                let buf = buffer.take().unwrap();
-                let xfer = tx.write(buf);
+            let mut tx = cx.local.tx.take().unwrap();
+            let mut txbuffer = cx.local.txbuffer.take().unwrap();
 
-                cx.local.delay_us.delay(1.secs());
-                cx.local.led.set_high();
+            txbuffer.copy_from_slice(*cx.shared.buffer);
+            let xfer = tx.write(txbuffer);
 
-                cx.local.delay_us.delay(1.secs());
-                cx.local.led.set_low();
+            cx.local.delay_us.delay(1.secs());
+            cx.local.led.set_high();
 
-                let (buf, tx) = xfer.wait();
-                buffer.replace(buf);
-                tx
-            });
+            cx.local.delay_us.delay(1.secs());
+            cx.local.led.set_low();
+
+            (txbuffer, tx) = xfer.wait();
+            cx.local.tx.replace(tx);
+            cx.local.txbuffer.replace(txbuffer);
         }
     }
 }