diff --git a/embassy-hal-common/src/lib.rs b/embassy-hal-common/src/lib.rs
index b2a35cd35..1b253719e 100644
--- a/embassy-hal-common/src/lib.rs
+++ b/embassy-hal-common/src/lib.rs
@@ -10,4 +10,5 @@ mod macros;
 mod peripheral;
 pub mod ratio;
 pub mod ring_buffer;
+pub mod stm32;
 pub use peripheral::{Peripheral, PeripheralRef};
diff --git a/embassy-hal-common/src/stm32/flash.rs b/embassy-hal-common/src/stm32/flash.rs
new file mode 100644
index 000000000..46c42aff9
--- /dev/null
+++ b/embassy-hal-common/src/stm32/flash.rs
@@ -0,0 +1,113 @@
+pub mod f4 {
+    const FLASH_BASE: u32 = 0x08_00_00_00;
+    pub(crate) const SMALL_SECTOR_SIZE: u32 = 16 * 1024;
+    pub(crate) const MEDIUM_SECTOR_SIZE: u32 = 64 * 1024;
+    pub(crate) const LARGE_SECTOR_SIZE: u32 = 128 * 1024;
+    pub const SECOND_BANK_SECTOR_OFFSET: u8 = 12;
+
+    #[derive(Debug, PartialEq)]
+    pub struct FlashSector {
+        pub index: u8,
+        pub size: u32,
+    }
+
+    pub fn get_sector(addr: u32, dual_bank: bool, flash_size: u32) -> FlashSector {
+        let offset = addr - FLASH_BASE;
+        if !dual_bank {
+            get_single_bank_sector(offset)
+        } else {
+            let bank_size = flash_size / 2;
+            if offset < bank_size {
+                get_single_bank_sector(offset)
+            } else {
+                let sector = get_single_bank_sector(offset - bank_size);
+                FlashSector {
+                    index: SECOND_BANK_SECTOR_OFFSET + sector.index,
+                    ..sector
+                }
+            }
+        }
+    }
+
+    fn get_single_bank_sector(offset: u32) -> FlashSector {
+        // First 4 sectors are 16KB, then one 64KB, and rest are 128KB
+
+        match offset / LARGE_SECTOR_SIZE {
+            0 => {
+                if offset < 4 * SMALL_SECTOR_SIZE {
+                    FlashSector {
+                        index: (offset / SMALL_SECTOR_SIZE) as u8,
+                        size: SMALL_SECTOR_SIZE,
+                    }
+                } else {
+                    FlashSector {
+                        index: 4,
+                        size: MEDIUM_SECTOR_SIZE,
+                    }
+                }
+            }
+            i => FlashSector {
+                index: 4 + i as u8,
+                size: LARGE_SECTOR_SIZE,
+            },
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::f4::*;
+
+    #[test]
+    fn can_get_sector_single_bank() {
+        let assert_sector = |index: u8, size: u32, addr: u32| {
+            assert_eq!(FlashSector { index, size }, get_sector(addr, false, 1024 * 1024))
+        };
+
+        assert_sector(0, SMALL_SECTOR_SIZE, 0x0800_0000);
+        assert_sector(0, SMALL_SECTOR_SIZE, 0x0800_3FFF);
+        assert_sector(3, SMALL_SECTOR_SIZE, 0x0800_C000);
+        assert_sector(3, SMALL_SECTOR_SIZE, 0x0800_FFFF);
+
+        assert_sector(4, MEDIUM_SECTOR_SIZE, 0x0801_0000);
+        assert_sector(4, MEDIUM_SECTOR_SIZE, 0x0801_FFFF);
+
+        assert_sector(5, LARGE_SECTOR_SIZE, 0x0802_0000);
+        assert_sector(5, LARGE_SECTOR_SIZE, 0x0803_FFFF);
+        assert_sector(11, LARGE_SECTOR_SIZE, 0x080E_0000);
+        assert_sector(11, LARGE_SECTOR_SIZE, 0x080F_FFFF);
+    }
+
+    #[test]
+    fn can_get_sector_dual_bank() {
+        let assert_sector = |index: u8, size: u32, addr: u32| {
+            assert_eq!(FlashSector { index, size }, get_sector(addr, true, 1024 * 1024))
+        };
+
+        assert_sector(0, SMALL_SECTOR_SIZE, 0x0800_0000);
+        assert_sector(0, SMALL_SECTOR_SIZE, 0x0800_3FFF);
+        assert_sector(3, SMALL_SECTOR_SIZE, 0x0800_C000);
+        assert_sector(3, SMALL_SECTOR_SIZE, 0x0800_FFFF);
+
+        assert_sector(4, MEDIUM_SECTOR_SIZE, 0x0801_0000);
+        assert_sector(4, MEDIUM_SECTOR_SIZE, 0x0801_FFFF);
+
+        assert_sector(5, LARGE_SECTOR_SIZE, 0x0802_0000);
+        assert_sector(5, LARGE_SECTOR_SIZE, 0x0803_FFFF);
+        assert_sector(7, LARGE_SECTOR_SIZE, 0x0806_0000);
+        assert_sector(7, LARGE_SECTOR_SIZE, 0x0807_FFFF);
+
+        assert_sector(12, SMALL_SECTOR_SIZE, 0x0808_0000);
+        assert_sector(12, SMALL_SECTOR_SIZE, 0x0808_3FFF);
+        assert_sector(15, SMALL_SECTOR_SIZE, 0x0808_C000);
+        assert_sector(15, SMALL_SECTOR_SIZE, 0x0808_FFFF);
+
+        assert_sector(16, MEDIUM_SECTOR_SIZE, 0x0809_0000);
+        assert_sector(16, MEDIUM_SECTOR_SIZE, 0x0809_FFFF);
+
+        assert_sector(17, LARGE_SECTOR_SIZE, 0x080A_0000);
+        assert_sector(17, LARGE_SECTOR_SIZE, 0x080B_FFFF);
+        assert_sector(19, LARGE_SECTOR_SIZE, 0x080E_0000);
+        assert_sector(19, LARGE_SECTOR_SIZE, 0x080F_FFFF);
+    }
+}
diff --git a/embassy-hal-common/src/stm32/mod.rs b/embassy-hal-common/src/stm32/mod.rs
new file mode 100644
index 000000000..2e50f82b3
--- /dev/null
+++ b/embassy-hal-common/src/stm32/mod.rs
@@ -0,0 +1 @@
+pub mod flash;