diff --git a/src/machine/board_arduino_uno_q.go b/src/machine/board_arduino_uno_q.go
index bf26eadb5..4d11ca217 100644
--- a/src/machine/board_arduino_uno_q.go
+++ b/src/machine/board_arduino_uno_q.go
@@ -7,54 +7,64 @@ package machine
 import (
 	"device/stm32"
 	"runtime/interrupt"
+	"unsafe"
 )
 
 const (
 	// Arduino Pins
-	A0 = PA0
-	A1 = PA1
-	A2 = PA4
-	A3 = PB1
-	A4 = PB11
-	A5 = PB12
+	A0 = PA4
+	A1 = PA5
+	A2 = PA6
+	A3 = PA7
+	A4 = PC1
+	A5 = PC0
 
 	D0  = PB7
 	D1  = PB6
-	D2  = PA10
-	D3  = PB3
-	D4  = PB5
-	D5  = PB4
-	D6  = PB10
-	D7  = PA8
-	D8  = PA9
-	D9  = PC7
-	D10 = PB0
-	D11 = PA7
-	D12 = PA6
-	D13 = PA5
-	D14 = PB9
-	D15 = PB8
+	D2  = PB3
+	D3  = PB0
+	D4  = PA12
+	D5  = PA11
+	D6  = PB1
+	D7  = PB2
+	D8  = PB4
+	D9  = PB8
+	D10 = PB9
+	D11 = PB15
+	D12 = PB14
+	D13 = PB13
+	D18 = PC1
+	D19 = PC0
+	D20 = PB10
+	D21 = PB11
 )
 
 const (
-	LED         = LED_BUILTIN
-	LED_BUILTIN = LED_GREEN
-	LED_GREEN   = PA5
+	LED    = LED3_R
+	LED3_R = PH10
+	LED3_G = PH11
+	LED3_B = PH12
+	LED4_R = PH13
+	LED4_G = PH14
+	LED4_B = PH15
 )
 
 const (
-	BUTTON = PC13
-)
+	// Default UART pins (LPUART1 active via ST-LINK virtual COM port)
+	UART_TX_PIN = PG7
+	UART_RX_PIN = PG8
 
-const (
-	// UART pins
-	// PA2 and PA3 are connected to the ST-Link Virtual Com Port (VCP)
-	UART_TX_PIN = PA2
-	UART_RX_PIN = PA3
+	// USART1 pins (Arduino header D1/D0)
+	UART1_TX_PIN = D1
+	UART1_RX_PIN = D0
+
+	// LPUART1 pins (active via ST-LINK virtual COM port)
+	UART2_TX_PIN = PG7
+	UART2_RX_PIN = PG8
 
 	// I2C pins
-	I2C0_SCL_PIN = PB8
-	I2C0_SDA_PIN = PB9
+	I2C0_SCL_PIN = D20
+	I2C0_SDA_PIN = D21
 
 	// SPI pins
 	SPI1_SCK_PIN = PA5
@@ -66,23 +76,31 @@ const (
 )
 
 var (
-	// USART2 is the hardware serial port connected to the onboard ST-LINK
-	// debugger to be exposed as virtual COM port over USB.
+	// USART1 on PB6/PB7 (Arduino header D1/D0).
 	UART1  = &_UART1
 	_UART1 = UART{
 		Buffer:            NewRingBuffer(),
-		Bus:               stm32.USART2,
+		Bus:               stm32.USART1,
 		TxAltFuncSelector: AF7_USART1_2_3,
 		RxAltFuncSelector: AF7_USART1_2_3,
 	}
-	DefaultUART = UART1
 
-	// I2C1 is documented, alias to I2C0 as well
-	I2C1 = &I2C{
-		Bus:             stm32.I2C1,
+	// LPUART1 on PG7/PG8 (active via ST-LINK virtual COM port).
+	UART2  = &_UART2
+	_UART2 = UART{
+		Buffer:            NewRingBuffer(),
+		Bus:               (*stm32.USART_Type)(unsafe.Pointer(stm32.LPUART1)),
+		TxAltFuncSelector: AF8_UART4_5_LPUART1_SDMMC1,
+		RxAltFuncSelector: AF8_UART4_5_LPUART1_SDMMC1,
+	}
+	DefaultUART = UART2
+
+	// I2C2 is documented, alias to I2C0 as well
+	I2C2 = &I2C{
+		Bus:             stm32.I2C2,
 		AltFuncSelector: AF4_I2C1_2_3_4,
 	}
-	I2C0 = I2C1
+	I2C0 = I2C2
 
 	// SPI1 is documented, alias to SPI0 as well
 	SPI1 = &SPI{
@@ -93,5 +111,6 @@ var (
 )
 
 func init() {
-	UART1.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART1.handleInterrupt)
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART1, _UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(stm32.IRQ_LPUART1, _UART2.handleInterrupt)
 }
diff --git a/src/machine/machine_stm32u5.go b/src/machine/machine_stm32u5.go
index 720e26ca2..19efa18ce 100644
--- a/src/machine/machine_stm32u5.go
+++ b/src/machine/machine_stm32u5.go
@@ -236,13 +236,16 @@ func (p Pin) enableClock() {
 	default:
 		panic("machine: unknown port")
 	}
+	// Dummy read-back to ensure the clock enable takes effect before
+	// accessing GPIO registers (2 AHB cycle delay per STM32 reference manual).
+	_ = stm32.RCC.AHB2ENR1.Get()
 }
 
 // Enable peripheral clock
 func enableAltFuncClock(bus unsafe.Pointer) {
 	switch bus {
 	case unsafe.Pointer(stm32.PWR): // Power interface clock enable
-		// PWR clock is always enabled on U5 (no dedicated enable bit needed)
+		stm32.RCC.AHB3ENR.SetBits(stm32.RCC_AHB3ENR_PWREN)
 	case unsafe.Pointer(stm32.I2C1): // I2C1 clock enable
 		stm32.RCC.APB1ENR1.SetBits(stm32.RCC_APB1ENR1_I2C1EN)
 	case unsafe.Pointer(stm32.I2C2): // I2C2 clock enable
diff --git a/src/machine/machine_stm32u585.go b/src/machine/machine_stm32u585.go
index f5e568bb3..5492e14e6 100644
--- a/src/machine/machine_stm32u585.go
+++ b/src/machine/machine_stm32u585.go
@@ -4,6 +4,7 @@ package machine
 
 import (
 	"device/stm32"
+	"unsafe"
 )
 
 func CPUFrequency() uint32 {
@@ -20,8 +21,23 @@ const APB2_TIM_FREQ = 4e6 // 4MHz (MSI default)
 
 // Configure the UART.
 func (uart *UART) configurePins(config UARTConfig) {
+	if uart.isLPUART1() {
+		// LPUART1 is on APB3. Explicitly enable its peripheral clock.
+		stm32.RCC.APB3ENR.SetBits(stm32.RCC_APB3ENR_LPUART1EN)
+		_ = stm32.RCC.APB3ENR.Get() // delay for clock stabilization
+
+		// Select PCLK3 as LPUART1 kernel clock source.
+		stm32.RCC.CCIPR3.ReplaceBits(
+			stm32.RCC_CCIPR3_LPUART1SEL_PCLK3<<stm32.RCC_CCIPR3_LPUART1SEL_Pos,
+			stm32.RCC_CCIPR3_LPUART1SEL_Msk, 0)
+	}
+
 	if config.RX.getPort() == stm32.GPIOG || config.TX.getPort() == stm32.GPIOG {
-		// Enable VDDIO2 power supply for PGx pins
+		// Enable VDDIO2 voltage monitoring and wait for ready before
+		// declaring VDDIO2 supply valid (matches HAL_PWREx_EnableVddIO2).
+		stm32.PWR.SetSVMCR_IO2VMEN(1)
+		for stm32.PWR.GetSVMSR_VDDIO2RDY() == 0 {
+		}
 		stm32.PWR.SetSVMCR_IO2SV(1)
 	}
 
@@ -30,9 +46,18 @@ func (uart *UART) configurePins(config UARTConfig) {
 	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }
 
+// isLPUART1 returns true if this UART is backed by the LPUART1 peripheral.
+func (uart *UART) isLPUART1() bool {
+	return uintptr(unsafe.Pointer(uart.Bus)) == uintptr(unsafe.Pointer(stm32.LPUART1))
+}
+
 // UART baudrate calc based on the bus and clockspeed
 // NOTE: keep this in sync with the runtime/runtime_stm32u5.go clock init code
 func (uart *UART) getBaudRateDivisor(baudRate uint32) uint32 {
+	if uart.isLPUART1() {
+		// LPUART uses BRR = 256 * fclk / baud
+		return (256 * CPUFrequency()) / baudRate
+	}
 	return CPUFrequency() / baudRate
 }
 
diff --git a/src/runtime/runtime_stm32u5.go b/src/runtime/runtime_stm32u5.go
index cd97531d1..3bed5fe0c 100644
--- a/src/runtime/runtime_stm32u5.go
+++ b/src/runtime/runtime_stm32u5.go
@@ -3,6 +3,7 @@
 package runtime
 
 import (
+	"device/stm32"
 	"machine"
 )
 
@@ -24,8 +25,9 @@ func buffered() int {
 
 func initCLK() {
 	// Use MSI at 4MHz — the reset default clock configuration.
-	// This matches the known-working bare-metal C configuration for
-	// the Arduino Uno Q (STM32U585). The MCU boots with MSI at 4MHz,
-	// VOS Range 4, and 0 flash wait states. No additional configuration
-	// is needed.
+	// The MCU boots with MSI at 4MHz, VOS Range 4, and 0 flash wait states.
+
+	// Enable PWR peripheral clock (required on STM32U5 before accessing PWR registers).
+	stm32.RCC.AHB3ENR.SetBits(stm32.RCC_AHB3ENR_PWREN)
+	_ = stm32.RCC.AHB3ENR.Get() // read-back for clock stabilization
 }