Initialization of real time clock on stm32f3 Discovery board

[smedellin90]

Hello!

I have not been able to find a way to initialize the rtc on the stm32f3 Discovery board.
For the STM32F103C8, initialization would go something like this (using cortex-m-rtfm crate):

use stm32f1xx_hal::{delay, gpio, i2c, rtc, spi, stm32, timer};

#[app(device = stm32f1xx_hal::stm32, peripherals = true)]
const APP: () = {
   
       #[init(spawn = [msg])]
       fn init(mut c: init::Context) -> init::LateResources {
           let mut rcc = c.device.RCC.constrain();
           let mut backup_domain = rcc
                .bkp
                .constrain(c.device.BKP, &mut rcc.apb1, &mut c.device.PWR);
           let mut rtc_dev = rtc::Rtc::rtc(c.device.RTC, &mut backup_domain); // initialization of rtc
           // rest is omitted
       }
}

Is there a way to initialize the real time clock currently using the stm32f3xx-hal?

[Sh3Rm4n]

Currently, the RTC module is missing from the stm32f3xx-hal. But the stm32f3-series do support RTCs, so it should be possible.

PRs for an rtc module are welcome! :)

[smedellin90]

I'm currently working on an RTC module for the stm32f3xx-hal. I'm running into a peculiar issue at the moment with the RTC init flag (RTC_ISR register, INITF bit). Below is a function that writes prescaler values into the PRER register:

    fn perform_prescaler_write(&mut self, prediv_s: u32, prediv_a: u32) {
        // Disabling write protection to RTC reg block
        self.regs.wpr.write(|w| unsafe { w.bits(0xCA) });
        self.regs.wpr.write(|w| unsafe { w.bits(0x53) });
        // Setting RTC Initialization bit to make prescalers programmable
        self.regs.isr.modify(|_, w| { w.init().set_bit()});
        // wait for initilization mode to take effect
        while self.regs.isr.read().initf().bit() == false {} // Never finishes
        // Setting Prescalers for 1 hz RTC
        let raw_bits: u32 = prediv_s | (prediv_a << 16);
        self.regs.prer.write(|w| unsafe { w.bits(raw_bits) });
        // Take device out of Initialization mode
        self.regs.isr.modify(|_, w| { w.init().clear_bit()});
        // wait for last write to be done
        while !self.regs.isr.read().initf().bit() == false {}
    }

It will get hung up, waiting for RTC initialization mode to be set. Has anyone run into this issue? I'm currently using the stm32f3 discovery board.

[David-OConnor]

Is this working now?