Hello,
On a STM32WB55REV, I'm having problems with going to standby.
These problems are intermittent (1 in 30 cycles maybe, sometimes 3 in a row, sometimes none for a hundred of cycles...).
I only started seeing them after I enabled BLE in my application (so before that I did not see them for the last year of development).
I'm using the stack BLE light v1.14.0, FUS is 1.2.0.
STM32_WPAN code is from FW 1.14.0, and started its life as the HRS_FreeRTOS example. The details of my target (no LSE, pin allocation) make running the vanilla example code a chore so I don't really have a "bare minimum" application I can refer to that would run on my target.
I tested my services on the Nucleo extensively though without any problem, and the BLE functionality of my device does not show any problems nor unexpected behavior.
The problem, from a brid's eye view, is that the device sometimes does not enter Standby properly after the BLE stack has run.
No link with what has happened during runtime that I can see (it my only advertise, or connect once, or connect/disconnect multiple times without effect on the bug appearing).
- LL_C2_PWR_SetPowerMode(LL_PWR_MODE_SHUTDOWN) is done before I start CPU2 with the example's "HW_IPCC_Enable()";
When I stop the BLE part of my application (code run only if BLE has been successfully started), I do:
- LL_PWR_DisableBootC2() (because I do not want it to resatart after standby)
- hci_reset() and check the status (always BLE_STATUS_SUCCESS);
When I go to standby, here is the code used. Some of it is maybe cargo-cult code that results from the numerous attempts to locate the problem...
// disable all interrupts
for( int i = 0; i<62; i++ ){ // IRQn_Type in stm32wb55xx.h shows the range
HAL_NVIC_DisableIRQ((IRQn_Type)i);
}
// SRAM2a retention needs 2 things: an Option byte set to avoid clearing the RAM on reset,
// and a flag to force the regulator to power the SRAM while in Standby mode.
HAL_PWREx_EnableSRAMRetention();
// Disable all used wakeup sources
LL_PWR_DisableWakeUpPin(BUTTON_IN_FLAG);
LL_PWR_DisableWakeUpPin(VBUS_WKUP_FLAG);
// Clear all wake up Flag
LL_PWR_ClearFlag_WU();
// Set wakeup pin polarity
BUTTON_IN_SET_WAKEUP_POLARITY();
VBUS_WKUP_SET_WAKEUP_POLARITY();
// Enable wakeup pin
LL_PWR_EnableWakeUpPin(BUTTON_IN_FLAG);
LL_PWR_EnableWakeUpPin(VBUS_WKUP_FLAG);
// As default button state is high level, need to clear all wake up Flag again
LL_PWR_ClearFlag_WU();
// Somhow the internal wakeup line seems to prevent us from entering low power sometime.
// The problem with this is that the User Manual is basically silent on what it is...
HAL_PWREx_DisableInternalWakeUpLine();
HAL_PWR_EnterSTANDBYMode();
Looking at the SFRs by setting a breakpoint after HAL_PWR_EnterSTANDBYMode(), there are no wakeup flags WUFx nor WUFI (anymore), no interrupts enabled (some are pending).
The low power modes of C1 and C2 are as expected (C2 LPMS = 0x4 and C1 LPMS = 0x3).
I just can't see any reason why it would not go to standby... Any idea ?
