Arduino for STM32

Thanks!
I did a little test. I made a timer interrupt every second, and counted seconds, minutes, and hours. Along with starting the program, I also started a timer on the phone. After 12 hours, he verified the testimony. The timer on STM32 showed a value of 3 seconds more than on the phone. This is ...

I do not need super high accuracy. + - 1-3 minutes a day - for me it is permissible.
I was just stuck with choosing a timing source. I need an interrupt every second. The RTClock library has such a function, but does not work on the kernel from STMicroelectronycs . The STM32RTC library runs on this ...

How accurate will the HardwareTimer be? If I count every second, what will be the difference with RTC?

Hello everyone!
I am using the STM32F103C8T6 board (blue pill) and kernel: "STM32 Cores by STMicroelectronycs" https://github.com/stm32duino/wiki/wiki/Getting-Started
I am using the STM32RTC library: https://github.com/stm32duino/STM32RTC
I need to call an interrupt 1 time per second. Can you give ...

Hello.
Sorry for my english. I use a translator.
I am using STM32F103C8T6 (Blue Pill).
I faced an incomprehensible situation. I want to make a device for testing Li-ion batteries. Here is a link to the device diagram: https://easyeda.com/igor.silenock/li-ion-batterycharger
Here is a sketch ...

Thank you, you helped me a lot!

Thanks!
Can you tell me how to disable SerialUSB?

Hello. I encountered a restriction on the use of pins. I need to use USB pins (PA11 and PA12) for my own purposes. But if I write a simple sketch, then the pin switching does not happen:
#define Pin1 PA11
#define Pin2 PA12

void setup() {
pinMode(Pin1, OUTPUT);
pinMode(Pin2, OUTPUT);
}

void loop ...

Hmm ... it’s not clear ... I just replaced PC13 with PA3 (for the test). There is PWM on PA3, but not on PC13. It seems that the PWM core is not configured for all pins.

I'm sorry, I forgot to indicate board. I am using STM32F103S8T6 (Blue Pill). The kernel is using this: https://github.com/stm32duino/Arduino_Core_STM32
For some reason, AnalogWright does not work. I tried like this, the result is the same:

void setup() {
pinMode(PC13, OUTPUT);
analogWrite(PC13 ...