diff --git a/semestralka_2_uart/src/bin/main.rs b/semestralka_2_uart/src/bin/main.rs
index d13f4fa..8055405 100644
--- a/semestralka_2_uart/src/bin/main.rs
+++ b/semestralka_2_uart/src/bin/main.rs
@@ -13,6 +13,7 @@ use dma_gpio::config::BAUD;
 use dma_gpio::wakeup::iwdg::{clear_wakeup_flags, init_watchdog_reset};
 use dma_gpio::sleep::shutdown;
 use dma_gpio::sleep::standby;
+use dma_gpio::sleep::stop3;
 use dma_gpio::hw_uart_pc::init::{init_hw_uart_to_pc, LowPowerCmd, CMD_CH};
 use {defmt_rtt as _, panic_probe as _};
 
@@ -45,7 +46,10 @@ async fn main(spawner: Spawner) {
            [1] Standby + 8 KB SRAM2 retention\n\
            [2] Standby + full SRAM2 retention\n\
            [3] Standby — minimal power, SRAM2 lost\n\
-           [4] Shutdown — lowest power, full reset on wake",
+           [4] Shutdown — lowest power, full reset on wake\n\
+           [5] STOP3 mode with WFI\n\
+           [6] STOP3 mode with WFE\n\
+           [7] STOP3 mode with WFE (no event clear)",
            BAUD, WATCHDOG_TIMEOUT_US / 1_000_000
     );
 
@@ -82,6 +86,21 @@ async fn main(spawner: Spawner) {
                 Timer::after(Duration::from_millis(10)).await;
                 shutdown::enter_shutdown();
             }
+            LowPowerCmd::Stop3Wfi => {
+                init_watchdog_reset(p.IWDG).await;
+                Timer::after(Duration::from_millis(10)).await;
+                stop3::enter_stop3(stop3::StopEntry::Wfi);
+            }
+            LowPowerCmd::Stop3Wfe => {
+                init_watchdog_reset(p.IWDG).await;
+                Timer::after(Duration::from_millis(10)).await;
+                stop3::enter_stop3(stop3::StopEntry::Wfe);
+            }
+            LowPowerCmd::Stop3WfeNoClear => {
+                init_watchdog_reset(p.IWDG).await;
+                Timer::after(Duration::from_millis(10)).await;
+                stop3::enter_stop3(stop3::StopEntry::WfeNoEventClear);
+            }
         }
     }
 }
diff --git a/semestralka_2_uart/src/hw_uart_pc/init.rs b/semestralka_2_uart/src/hw_uart_pc/init.rs
index 1b8263f..5d47381 100644
--- a/semestralka_2_uart/src/hw_uart_pc/init.rs
+++ b/semestralka_2_uart/src/hw_uart_pc/init.rs
@@ -27,6 +27,9 @@ pub enum LowPowerCmd {
     StandbyFull,   // 2
     Standby,       // 3
     Shutdown,      // 4
+    Stop3Wfi,
+    Stop3Wfe,
+    Stop3WfeNoClear,
 }
 
 pub static CMD_CH: Channel<CriticalSectionRawMutex, LowPowerCmd, 1> = Channel::new();
@@ -35,7 +38,7 @@ pub static CMD_CH: Channel<CriticalSectionRawMutex, LowPowerCmd, 1> = Channel::n
 pub async fn uart_cmd_task() {
     // Prompt once
     let _ = PIPE_HW_TX
-        .write(b"Modes: 1=SB8, 2=SBfull, 3=SB, 4=SD\r\n")
+        .write(b"Modes: 1=SB8, 2=SBfull, 3=SB, 4=SD, 5=STOP3(WFI), 6=STOP3(WFE), 7=STOP3(WFE no clear)\r\n")
         .await;
 
     let mut b = [0u8; 1];
@@ -61,8 +64,22 @@ pub async fn uart_cmd_task() {
                 let _ = PIPE_HW_TX.write(b"ACK 4: shutdown\r\n").await;
                 CMD_CH.send(LowPowerCmd::Shutdown).await;
             }
+            b'5' => {
+                let _ = PIPE_HW_TX.write(b"ACK 5: STOP3 with WFI\r\n").await;
+                CMD_CH.send(LowPowerCmd::Stop3Wfi).await;
+            }
+            b'6' => {
+                let _ = PIPE_HW_TX.write(b"ACK 6: STOP3 with WFE\r\n").await;
+                CMD_CH.send(LowPowerCmd::Stop3Wfe).await;
+            }
+            b'7' => {
+                let _ = PIPE_HW_TX.write(b"ACK 7: STOP3 with WFE (no event clear)\r\n").await;
+                CMD_CH.send(LowPowerCmd::Stop3WfeNoClear).await;
+            }
             b'\r' | b'\n' | b' ' => {}
-            _ => { let _ = PIPE_HW_TX.write(b"ERR: use 1|2|3|4\r\n").await; }
+            _ => {
+                let _ = PIPE_HW_TX.write(b"ERR: use 1|2|3|4|5|6|7\r\n").await;
+            }
         }
         yield_now().await;
     }
diff --git a/semestralka_2_uart/src/sleep/mod.rs b/semestralka_2_uart/src/sleep/mod.rs
index eec9227..4317160 100644
--- a/semestralka_2_uart/src/sleep/mod.rs
+++ b/semestralka_2_uart/src/sleep/mod.rs
@@ -2,3 +2,4 @@
 
 pub mod standby;
 pub mod shutdown;
+pub mod stop3;
diff --git a/semestralka_2_uart/src/sleep/stop3.rs b/semestralka_2_uart/src/sleep/stop3.rs
new file mode 100644
index 0000000..72dad33
--- /dev/null
+++ b/semestralka_2_uart/src/sleep/stop3.rs
@@ -0,0 +1,39 @@
+// src/sleep/stop3.rs
+
+// #define PWR_STOPENTRY_WFI              (0x01U) //*!< Wait For Interruption instruction to enter Stop mode */
+// #define PWR_STOPENTRY_WFE              (0x02U) //*!< Wait For Event instruction to enter Stop mode        */
+// #define PWR_STOPENTRY_WFE_NO_EVT_CLEAR (0x03U)
+
+/// How to enter STOP3 mode
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum StopEntry {
+    Wfi,
+    Wfe,
+    WfeNoEventClear,
+}
+
+impl From<StopEntry> for u8 {
+    fn from(value: StopEntry) -> Self {
+        match value {
+            StopEntry::Wfi => 0x01,
+            StopEntry::Wfe => 0x02,
+            StopEntry::WfeNoEventClear => 0x03,
+        }
+    }
+}
+pub fn enter_stop3(stop_entry: StopEntry) -> ! {
+    unsafe extern "C" {
+        fn HAL_PWREx_EnterSTOP3Mode(stop_entry: u8);
+    }
+
+    unsafe {
+        HAL_PWREx_EnterSTOP3Mode(stop_entry.into());
+    }
+
+    cortex_m::asm::udf(); //panic
+}
+
+// Example usage:
+// enter_stop3(StopEntry::Wfi);
+// enter_stop3(StopEntry::Wfe);
+// enter_stop3(StopEntry::WfeNoEventClear);