Summary

This PR fixes the necessary initialization procedures which should be run before user code is called.

premain() function in main.cpp is essential for the HAL library to initize properly, more specifically it called HAL_Init which setup the systick interrupt handler which is necessary for writing a hello world.....

The issue #869 has already mentioned this bug but didn't find a solution to it. After some trials and errors and comparasion between assemblies for different products, the patch here is likely solving it.

If possible, is there's any chance we talk about this a bit further because I don't know why this workaround works in fact...

Validation

• Ensure CI build is passed.
  • CI should run after the PR is posted. let's see the result 😉
• Demonstrate the code is solid.
  • The demostration is based on my fork supporting generic STM32F105Cx boards, which is located here (https://github.com/ttimasdf/Arduino_Core_STM32/tree/variant-generic-stm32f105x).

Demostration:

Detail step-by-step is To-Be-Filled. The following code is a modified blinking LED use loop based manual_delay() and HAL provided delay() altogether. The original delay() would stuck if HAL_Init is not called beforehand, the same as described in #869.

/*
 * Blink
 * Turns on an LED on for one second,
 * then off for one second, repeatedly.
 */

#include <Arduino.h>

#ifndef LED_BUILTIN
  #define LED_BUILTIN PD2
#endif

uint32_t manual_delay(volatile uint32_t time) {
  volatile uint32_t factor = 0xFF, i = time;
  while (factor > 0) {
    while (i > 0)  {
      i -= 1;
    }
    factor -= 1;
  }
  return time;
}

uint32_t blink(int pin, int times) {
  int i = times;
  while (i > 0) {
    uint32_t delay = 0xFFFF * 4;
    // turn the LED on (HIGH is the voltage level)
    digitalWrite(LED_BUILTIN, HIGH);
    manual_delay(delay);
    // wait for a second
    // delay(1000);
    // turn the LED off by making the voltage LOW
    digitalWrite(LED_BUILTIN, LOW);
    manual_delay(delay);
    // wait for a second
    // delay(1000);

    i -= 1;
  }
  return i;
}

void setup()
{
  // initialize LED digital pin as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop()
{
  blink(LED_BUILTIN, 10);
  delay(1000);
}

Code formatting

• Ensure AStyle check is passed thanks CI

Closing issues

Fixes #869