STM32WB55 BLE and LPM

[MahmoudAhmed11]

Hello,

I am using p-nucleo-wb55. I have a code with an RTC alarm interrupt triggered every 5 seconds. In the ISR, I set a sequencer task that sends a message via BLE. I have enabled the LPM as I want the MCU to enter sleep mode while it isn't working and only wakeup with the RTC alarm. I realized that the MCU doesn't stay in the sleep mode and when I debug, I realized that it wakes up so fast as the IPCC RX Interrupt is triggered continuously with high frequency.
How can I control this, knowing that I don't need the MCU to do any task through those 5 seconds, I just want it to sleep and wakeup only after 5 seconds.

Thanks in advance

[MahmoudAhmed11]

Hello @FilipKremen 

Yes, I have checked and I can't find a solution to my problem.
Why shouldn't I add code in the main? I just put it in to make it easier to detect whether the MCU enters sleep mode or keeps blinking.

[FilipKremen]

Hello,

the LED keeps blinking because BLE advertising is running and it wakes up the MCU. If you comment this line  Adv_Request(APP_BLE_FAST_ADV); in app_ble.c file, it stops blinking.

I recommend reading low power section in STM32WB55 datasheet. (3.7.5)

Datasheet - STM32WB55xx STM32WB35xx - Multiprotocol wireless 32-bit MCU Arm<Sup>®</Sup>-based Cortex<Sup>®</Sup>-M4 with FPU, Bluetooth<Sup>®</Sup> 5.4 and 802.15.4 radio solution

Best regards,

Filip Kremen

[mgatti]

Hello @MahmoudAhmed11 

I have a configuration similar to yours in which I only need to transmit the data contained in the advertisement.

I'll try to explain to you what I did, I hope you understand.

In the Adv_Cancel function, I added:

/* USER CODE BEGIN Adv_Cancel_2 */

activeFlag = false;
LL_C2_PWR_SetPowerMode(LL_PWR_MODE_SHUTDOWN);

/* USER CODE END Adv_Cancel_2 */

activeFlag is a boolean global variable (initialized to false)

Then I have the function:

static void Adv_Cancel_Req(void) {
/* USER CODE BEGIN Adv_Cancel_Req_1 */

/* USER CODE END Adv_Cancel_Req_1 */
UTIL_SEQ_SetTask(1 << CFG_TASK_ADV_CANCEL_ID, CFG_SCH_PRIO_0);
/* USER CODE BEGIN Adv_Cancel_Req_2 */

/* USER CODE END Adv_Cancel_Req_2 */
return;
}

And the function:

void Adv_Start(void) {

// ... manufacturer specific data update (into advertising array)

/**
* Start to Advertise to be connected by a Client
*/
Adv_Request(APP_BLE_FAST_ADV);

HW_TS_Start(myTimerFlag, (ADVERTISING_TIMEOUT_MS * 1000 / CFG_TS_TICK_VAL));
return;
}

In the APP_BLE_Init() function, I added:

/* USER CODE BEGIN APP_BLE_Init_2 */

HW_TS_Create(CFG_TIM_STOP_ADV, &(myTimerFlag), hw_ts_SingleShot, Adv_Cancel_Req);

/* USER CODE END APP_BLE_Init_2 */

In the while(1) loop, I don't directly call the MX_APPE_Process() function, but I call a state machine whose main states are:

1. I acquire a series of data
2. I transmit the packet; this state is in turn made up of several states:
   • "Initialization" state: if the activeFlag flag is false, I execute MX_APPE_Init() and set activeFlag=true
   • "Send data" state: I call the MX_APPE_Process() and Adv_Start() functions
   • "Wait" state: As long as the activeFlag flag is true, I continue to call the MX_APPE_Process() function; otherwise, I move to the next state.
3. I put the microcontroller to sleep and ensure that, upon waking, it restarts from step 1.

This ensures that the device functions correctly. Each time I invoke the transmission procedure, packets are sent for a time equal to ADVERTISING_TIMEOUT_MS (I set it to 1000, or 1 second).

I hope the explanation is clear and that it can be of help to you.

What I haven't been able to achieve, however, is achieve similar behavior when enabling the Eddystone TML Beacon protocol (in STM32CubeMX: BT SIG Beacon = EDDYSTONE_TLM_BEACON).

I hope someone can help me.