ChibiOS Free Embedded RTOS

Is the xtal present on the board? Is the RTC clock enabled?

Yes, the cristal is present. The LSE init is done flawlessly, the problem is with the RTC init.
I have tried with LSI as RTC source, but problem remains.
I have verified that VBAT pin is connected to VDD on the board.
I have tried with another nucleo board since i had ordered two of them.

What is strange, is that i cannot write in the RTC registers, whatever i write, if i read them afterward, all the registers are zeroed.

Theses register are protected by a mechanism :

After system reset, the RTC registers are protected against parasitic write access by
clearing the DBP bit in the PWR_CR1 register (refer to the power control section). DBP bit
must be set in order to enable RTC registers write access.
After Backup domain reset, all the RTC registers are write-protected. Writing to the RTC
registers is enabled by writing a key into the Write Protection register, RTC_WPR.
The following steps are required to unlock the write protection on all the RTC registers
except for RTC_TAMPCR, RTC_BKPxR, RTC_OR and RTC_ISR[13:8].
1. Write ‘0xCA’ into the RTC_WPR register.
2. Write ‘0x53’ into the RTC_WPR register.

but the chibios hal take care of this, and this is the same code on F746 (where it works) than on F767.

I hope this is not a side effect of having a 'A' revision chip soldered on this devboard ?

Alexandre

You should check erratas, because all other STM32s are fine with that driver.

Also try another board, it could be just that one device.

Giovanni

You should check erratas, because all other STM32s are fine with that driver.

Just read the errata, but nothing about RTC

Also try another board, it could be just that one device.

I have tried the two nucleo F767 that i have and both behave the same. I will order a F769 Discovery to see if there is the same problem on it.

I have compiled the RTC example from STM32Cube_FW_F7_V1.4.0 for the nucleo F767, and it fails at the exactly same place that the ChibiOS driver :
in the waiting loop for raise of RTC_ISR_INITF bit (which never raise).

I am now sure that it's not ChibiOS fault, and i will go on ST forum to investigate.

Perhaps it's a change in the RTC hardware that hardware people have not transmitted to the doc and the software guys, or a silicon bug specific to F767ZI Rev A ?

I leave tonight for a 3 weeks holidays, i think this problem will wait until my return

Alexandre

Have nice vacations

Giovanni