double framebuffer

kernel/pimoroni2w.x

@@ -2,7 +2,7 @@ MEMORY {
     FLASH : ORIGIN = 0x10000000, LENGTH = 16M - 4K
 
     RAM : ORIGIN = 0x20000000, LENGTH = 512K
-    SRAM4 : ORIGIN = 0x20080000, LENGTH = 4K
+    # SRAM4 : ORIGIN = 0x20080000, LENGTH = 4K
     SRAM5 : ORIGIN = 0x20081000, LENGTH = 4K
 }
 

kernel/src/display.rs

@@ -1,6 +1,6 @@
+use crate::framebuffer::{self, AtomicFrameBuffer};
+use alloc::vec;
 use core::sync::atomic::{AtomicBool, Ordering};
-
-use crate::framebuffer::AtomicFrameBuffer;
 use embassy_rp::{
     Peri,
     gpio::{Level, Output},
@@ -44,6 +44,10 @@ pub async fn init_display(
     unsafe { FRAMEBUFFER.draw(&mut display).await.unwrap() }
     display.set_on().await.unwrap();
 
+    // create double buffer if board has psram
+    #[cfg(feature = "pimoroni2w")]
+    framebuffer::init_double_buffer();
+
     display
 }
 
@@ -59,6 +63,13 @@ pub async fn display_handler(mut display: DISPLAY) {
             }
         }
 
-        Timer::after_millis(10).await;
+        // Only do swap if feature enabled
+        #[cfg(feature = "pimoroni2w")]
+        {
+            framebuffer::swap_buffers();
+        }
+
+        // small yield to allow other tasks to run
+        Timer::after_nanos(100).await;
     }
 }

kernel/src/framebuffer.rs

@@ -26,6 +26,24 @@ const SIZE: usize = SCREEN_HEIGHT * SCREEN_WIDTH;
 
 static mut BUFFER: [u16; SIZE] = [0; SIZE];
 
+#[cfg(feature = "pimoroni2w")]
+static mut DOUBLE_BUFFER: Option<alloc::vec::Vec<u16>> = None;
+
+#[cfg(feature = "pimoroni2w")]
+pub fn init_double_buffer() {
+    unsafe { DOUBLE_BUFFER = Some(alloc::vec![0_u16; SIZE]) };
+}
+
+#[cfg(feature = "pimoroni2w")]
+pub fn swap_buffers() {
+    unsafe {
+        core::mem::swap(
+            &mut BUFFER[..].as_mut_ptr(),
+            &mut DOUBLE_BUFFER.as_mut().unwrap().as_mut_slice().as_mut_ptr(),
+        );
+    }
+}
+
 static mut DIRTY_TILES: LazyLock<heapless::Vec<AtomicBool, TILE_COUNT>> = LazyLock::new(|| {
     let mut tiles = Vec::new();
     for _ in 0..TILE_COUNT {