Merge branch 'topic/stm32_uart' into 'master'

Avoid losing input bytes in the UART on STM32F4xx. Closes #117 See merge request eng/toolchain/bb-runtimes!152
AdaCore · Jan 28, 2025 · 589195b · 589195b
2 parents 032500b + 6239ceb
commit 589195b
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diff --git a/src/s-textio__stm32f4.adb b/src/s-textio__stm32f4.adb
@@ -107,7 +107,12 @@ package body System.Text_IO is
 
    procedure Put (C : Character) is
    begin
-      USART1_Periph.DR.DR := Character'Pos (C);
+      USART1_Periph.DR :=
+        (DR     => Character'Pos (C),
+         others => 0);
+      --  By assigning all fields of the DR register we can be sure that the
+      --  compiler does not use the read-modify-write sequence, which resets
+      --  the SR.RXNE flag.
    end Put;
 
    ----------------------------

diff --git a/src/s-textio__stm32f469.adb b/src/s-textio__stm32f469.adb
@@ -110,7 +110,12 @@ package body System.Text_IO is
 
    procedure Put (C : Character) is
    begin
-      USART6_Periph.DR.DR := Character'Pos (C);
+      USART6_Periph.DR :=
+        (DR     => Character'Pos (C),
+         others => 0);
+      --  By assigning all fields of the DR register we can be sure that the
+      --  compiler does not use the read-modify-write sequence, which resets
+      --  the SR.RXNE flag.
    end Put;
 
    ----------------------------