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while DMA2D_Periph.BGPFCCR.START loop
-- Wait for CLUT loading...
null;
end loop;
end if;
Function Definition: procedure Demo_Timer_PWM is -- low-level demo of the PWM capabilities
Function Body: Period : constant := 1000;
Output_Channel : constant Timer_Channel := Channel_2;
-- The LED driven by this example is determined by the channel selected.
-- That is so because each channel of Timer_4 is connected to a specific
-- LED in the alternate function configuration on this board. We will
-- initialize all of the LEDs to be in the AF mode for Timer_4. The
-- particular channel selected is completely arbitrary, as long as the
-- selected GPIO port/pin for the LED matches the selected channel.
--
-- Channel_1 is connected to the green LED.
-- Channel_2 is connected to the orange LED.
-- Channel_3 is connected to the red LED.
-- Channel_4 is connected to the blue LED.
--------------------
-- Configure_LEDs --
--------------------
procedure Configure_LEDs;
procedure Configure_LEDs is
begin
Enable_Clock (GPIO_D);
Configure_IO
(All_LEDs,
(Mode_AF,
AF => GPIO_AF_TIM4_2,
AF_Speed => Speed_50MHz,
AF_Output_Type => Push_Pull,
Resistors => Floating));
end Configure_LEDs;
-- The SFP run-time library for these boards is intended for certified
-- environments and so does not contain the full set of facilities defined
-- by the Ada language. The elementary functions are not included, for
-- example. In contrast, the Ravenscar "full" run-times do have these
-- functions.
function Sine (Input : Long_Float) return Long_Float;
-- Therefore there are four choices: 1) use the "ravescar-full-stm32f4"
-- runtime library, 2) pull the sources for the language-defined elementary
-- function package into the board's run-time library and rebuild the
-- run-time, 3) pull the sources for those packages into the source
-- directory of your application and rebuild your application, or 4) roll
-- your own approximation to the functions required by your application.
-- In this demonstration we roll our own approximation to the sine function
-- so that it doesn't matter which runtime library is used.
function Sine (Input : Long_Float) return Long_Float is
Pi : constant Long_Float := 3.14159_26535_89793_23846;
X : constant Long_Float := Long_Float'Remainder (Input, Pi * 2.0);
B : constant Long_Float := 4.0 / Pi;
C : constant Long_Float := (-4.0) / (Pi * Pi);
Y : constant Long_Float := B * X + C * X * abs (X);
P : constant Long_Float := 0.225;
begin
return P * (Y * abs (Y) - Y) + Y;
end Sine;
-- We use the sine function to drive the power applied to the LED, thereby
-- making the LED increase and decrease in brightness. We attach the timer
-- to the LED and then control how much power is supplied by changing the
-- value of the timer's output compare register. The sine function drives
-- that value, thus the waxing/waning effect.
begin
Configure_LEDs;
Enable_Clock (Timer_4);
Reset (Timer_4);
Configure
(Timer_4,
Prescaler => 1,
Period => Period,
Clock_Divisor => Div1,
Counter_Mode => Up);
Configure_Channel_Output
(Timer_4,
Channel => Output_Channel,
Mode => PWM1,
State => Enable,
Pulse => 0,
Polarity => High);
Set_Autoreload_Preload (Timer_4, True);