ARM Embedded Tutorial - Raspberry Pi Pico running at full CPU speed

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In the simple Blinky example we did the bare minimum that is necessary to blink a LED.

Now we increase CPU speed to full power with the help of the init_clock procedure from clocks.c.obj.

First step we need to do is to add the clocks.c.obj file to our code. When we do that and compile the code we are left again with linking errors because clocks.c.obj has dependencies on other code parts.

After fiddling arround a bit we end up with the needed list of dependencies to link in:

    program Blinky;
    {$L platform.c.obj}
    {$L gpio.c.obj}
    {$L clocks.c.obj}
    {$L xosc.c.obj}
    {$L pll.c.obj}
    {$L platform.c.obj}
    {$L watchdog.c.obj}

Now we add clocks_init to our code and we are also now able to initialize all peripherals:

    procedure runtime_init;
    const
      RESETS_SAFE_BITS=     %1111111111100110110111111;
      RESETS_PRECLOCK_BITS= %0001111000100110110111110;
      RESETS_POSTCLOCK_BITS=%1110000111000000000000001;
    begin
      resets.reset_set := RESETS_SAFE_BITS;
      resets.reset_clr := RESETS_PRECLOCK_BITS;
      repeat
      until (resets.reset_done and RESETS_PRECLOCK_BITS) = RESETS_PRECLOCK_BITS;
      clocks_init;
      resets.reset_clr := RESETS_POSTCLOCK_BITS;
      repeat
      until (resets.reset_done and RESETS_POSTCLOCK_BITS) = RESETS_POSTCLOCK_BITS;
    end;

We start the compiler again and there is still one dependency missing, so we add a bit of code to get this fixed:

    function __aeabi_uidiv(const numerator : uint32; denominator : uint32):uint32;  public name '__aeabi_uidiv';
    begin
      Result := numerator div denominator;
    end;

This dependency comes with the gcc compiler but we are lazy and use this simple (likely slower) alternative.

After this final step we are able to blink the LED's at full CPU speed, so we increase our delay loop because we are now faster with waiting:

    program Blinky;

    {$L platform.c.obj}
    {$L gpio.c.obj}
    {$L clocks.c.obj}
    {$L xosc.c.obj}
    {$L pll.c.obj}
    {$L watchdog.c.obj}

    procedure clocks_init; external;
    procedure gpio_init(gpio : longWord); external;

    function __aeabi_uidiv(const numerator : uint32; denominator : uint32):uint32;  public name '__aeabi_uidiv';
    begin
      Result := numerator div denominator;
    end;

    procedure runtime_init;
    const
      RESETS_SAFE_BITS=     %1111111111100110110111111;
      RESETS_PRECLOCK_BITS= %0001111000100110110111110;
      RESETS_POSTCLOCK_BITS=%1110000111000000000000001;
    begin
      resets.reset_set := RESETS_SAFE_BITS;
      resets.reset_clr := RESETS_PRECLOCK_BITS;
      repeat
      until (resets.reset_done and RESETS_PRECLOCK_BITS) = RESETS_PRECLOCK_BITS;
      clocks_init;
      resets.reset_clr := RESETS_POSTCLOCK_BITS;
      repeat
      until (resets.reset_done and RESETS_POSTCLOCK_BITS) = RESETS_POSTCLOCK_BITS;
    end;

    procedure gpio_set_dir(gpio : longWord; &out : longbool);
    var
      mask : longWord;
    begin
      mask := 1 shl  gpio;
      if out = true then
        sio.gpio_oe_set := mask
      else
        sio.gpio_oe_clr := mask;
    end;

    procedure gpio_put(gpio : longWord; value : boolean);
    var
      mask : longWord;
    begin
      mask := 1 shl gpio;
      if value=true then
        sio.gpio_set := mask
      else
        sio.gpio_clr := mask;
    end;

    const
      LED_PIN=25;
      GPIO_OUT=true;
    var
      i : longWord;
    begin
      runtime_init;
      gpio_init(LED_PIN);
      gpio_set_dir(LED_PIN,GPIO_OUT);
      repeat
        gpio_put(LED_PIN,true);
        for i := 0 to 3000000 do ;
        gpio_put(LED_PIN,false);
        for i := 0 to 3000000 do ;
      until 1=0;
    end.