STM32U575 Wakeup from UART in stop mode 1

[Alan01252]

Hi all,

I've been struggling so much to get wake from uart working on this board. 

It looks like it should be simple, I have this code which I am pretty sure should be everything needed, but it just doesn't wake up when I send data to the serial port.

Can anyone see what I might be missing?

#include <Arduino.h>
#include <stm32u5xx_hal.h>
#include <stm32u5xx_ll_usart.h>
#include <stm32u5xx_ll_bus.h>
#include "CustomPinsHub.h"
static constexpr uint32_t LED_PIN = LED1_GRN;
uint8_t aRxBuffer[10];

void SystemClock_Config(); // forward

HardwareSerial stlinkSerial(rx_pin2debug, tx_pin2debug);

void setup()
{
    stlinkSerial.begin(115200);
    HAL_PWREx_EnableUltraLowPowerMode();
    pinMode(LED1_GRN, OUTPUT);
    digitalWrite(LED1_GRN, LOW);
    stlinkSerial.println("→ Setup complete. LED is ON.");
    delay(500);
    UART_HandleTypeDef *huart = stlinkSerial.getHandle();
    UART_WakeUpTypeDef wudata{};
    wudata.WakeUpEvent = UART_WAKEUP_ON_READDATA_NONEMPTY;
    HAL_UARTEx_StopModeWakeUpSourceConfig(huart, wudata);
    __HAL_RCC_PWR_CLK_ENABLE();
    __HAL_UART_ENABLE_IT(huart, UART_IT_WUF);
    HAL_UARTEx_EnableStopMode(huart);
    HAL_UART_Receive_IT(huart, (uint8_t *)aRxBuffer, 10);
    stlinkSerial.println("Entering STOP-1, waiting for any RX data to wake me..");
    stlinkSerial.flush();
    delay(500);
    HAL_SuspendTick();
    HAL_PWREx_EnterSTOP1Mode(PWR_STOPENTRY_WFI);
    HAL_ResumeTick();
    SystemClock_Config();
    delay(500);
    stlinkSerial.println("✔ Woke up from STOP-1! Led off");
    delay(500);
    digitalWrite(LED_PIN, HIGH);
}

void loop()
{
    // nothing
}

[Saket_Om]

Hello @Alan01252 

Please refer to the example below: 

STM32CubeU5/Projects/NUCLEO-U575ZI-Q/Examples/UART/UART_WakeUpFromStopUsingFIFO at main · STMicroelectronics/STM32CubeU5 · GitHub

[Alan01252]

Thanks for the swift reply, but I amm very confused, I can't see anything I am missing in that example and what the code above.. Other than 

EXTI10_Wakeup_Enable

but that doesn't actually seem to have any implementation behind it?

[Saket_Om]

Try to make UART receive work before implementing the stop and waking up mode.

[Alan01252]

Apologies, just to be clear, receive and transmit do work.

I can do a simple ping/pong when the chip is awake. What I can't do is a get the board to wake up from sleep :(