"STM32. Net MF Development Board Learning-12" bouncing notes (PWM synthesis)

Besides driving the motor, PWM can also set different frequencies to simulate the notes output of different scales, the actual test found that the sound is quite beautiful, but the common active buzzer can not (Red Cattle Development Board from the belt), the need for specialized procurement of passive buzzer, the difference between the two is the active buzzer power on the ring, But the passive buzzer needs to enter a certain frequency signal to be audible.

We use Timer3 as the output source of PWM, we count fixed to 36, duty ratio is fixed to 1/2, through the frequency factor to set the corresponding PWM output frequency.

The underlying code is as follows, because the official no PWM driver template, the following functions are defined by me.

//采用Timer3 36M　PB0输出
　 CPU_TIMER_Initialize(timer,36,PSC,Music_ISR,(void *)timer);
　 CPU_TIMER_SetCCR(timer,2,param0==0 ? 0:18);
　 UINT32 m_Count= param0*param1/1000;
　 CPU_TIMER_SetCCM(timer,2,6);　//PWM1模式
　 CPU_TIMER_PWM_Start(timer,2);
　 CPU_TIMER_Start(timer);

Note frequency corresponds to the table below, according to which we can output the notes of different scales through PWM:

Notes	Frequency/hz	Semi-periodic/US	Notes	Frequency/hz	Semi-periodic/US	Notes	Frequency/hz	Semi-periodic/US
Low	Sound	Area	In	Sound	Area	High	Sound	Area
1	262	1908	1	523	0956	1	1046	0478
A	277	1805	A	554	0903	A	1109	0451
2	294	1700	2	578	0842	2	1175	0426
2#	311	1608	2#	622	0804	2#	1245	0402
3	330	1516	3	659	0759	3	1318	0372
4	349	1433	4	698	0716	4	1397	0358
4#	370	1350	4#	740	0676	4#	1480	0338
5	392	1276	5	784	0638	5	1568	0319
5#	415	1205	5#	831	0602	5#	1661	0292
6	440	1136	6	880	0568	6	1760	0284
6#	466	1072	6#	932	0536	6#	1865	0268
7	494	1012	7	988	0506	7	1976	0253

"#" means a flat, used to rise or fall half a sound, multiplied by two to raise the sound of a eight-degree scale, halved to a eight degree.

Taking into account the IO driver, so add a NPN transistor as the magnification output (the actual test, the effect is not obvious, and direct drive difference is not small), the schematic diagram is as follows: