本帖最后由 黑皮男 于 2018-3-27 20:57 编辑
X. d. Y: [0 ?- M, Z/ k
, G7 x- u+ B% S6 M5 d! R2 L产生两种交替的高频pwm,最佳的组合就是使用主从定时器模式。一个定时器做主,用来产生pwm,另一个从定时器对主定时器进行计数,当产生足够数量的脉冲后,在从定时器的中断中更改主定时器的ARR和CCR的值,来更改定时器的pwm频率。但是当频率很高的时候,两种频率进行切换的时候,中间由于代码的延时,切换处的脉冲信号会有误差,不会和两种频率PWM的周期相同,这个对我的应用是能够满足的。目前测的2M以下的频率计数比较准确。下面是部分代码实现,只做原理说明,代码无法拿来直接用,需要一些其他相关配置,平台是nucleo-f303,主定时器是TIM2,从定时器是TIM15。请见谅,没有准备图! q8 F" G: l/ E2 o; ]
9 O1 k X' `: Y主要步骤:
O; L0 Y( _% h1、主定时器初始化,设置好初始pwm频率
0 i3 ~! U o7 N- L% Y2、从定时器初始化,连接到主定时器
# ?( ?9 `; a# C( N* K2 Q3、启动定时器
5 S' z- G9 }& n% T: K4、从定时器计数符合要求脉冲数,产生中断,切换主定时器的pwm频率
( Z4 E1 a n, Q5 ^
7 V, L: U2 m( j) M主定时器初始化3 |$ p/ q/ {1 o. w/ K% G4 _
- LL_TIM_SetClockSource(TIM2, LL_TIM_CLOCKSOURCE_INTERNAL);5 b/ K6 [2 E1 z2 |9 R
- LL_TIM_SetClockDivision(TIM2, LL_TIM_CLOCKDIVISION_DIV1);) S" E! G; Q k! j t
-
" ^5 u( _4 I; Y - LL_TIM_SetTriggerOutput(TIM2, LL_TIM_TRGO_UPDATE);//主定时器主模式,更新事件产生触发信号到从定时器
( E/ t& g6 A/ X2 b' Z5 u( i( k( F9 ~! R - 5 i5 O+ G: C( o
- LL_TIM_SetCounterMode(TIM2, LL_TIM_COUNTERMODE_UP); 9 y6 F7 f2 t \
-
$ y# m2 p/ ~6 r8 V - LL_TIM_SetPrescaler(TIM2, SLOW_FREQ_PRESCALER);
/ Y$ ]. s9 g H8 V -
+ V3 P1 F, X8 s9 [1 O% K9 v - LL_TIM_EnableARRPreload(TIM2);
6 ^4 ~& V4 l7 t5 J1 R - & e- N1 Q. w( {: Z& }" N
- LL_TIM_SetAutoReload(TIM2, SLOW_FREQ_RELOAD);& p: W6 _3 T# w' B f7 J
- 6 ~0 ^: S) ]# f2 w
- LL_TIM_OC_SetMode(TIM2, PWM_CHANNEL, LL_TIM_OCMODE_PWM2);
' i2 D, r8 F1 \( U! X4 a) \ -
! M3 Z/ \- i( F G1 w+ n - LL_TIM_OC_SetPolarity(TIM2, PWM_CHANNEL, LL_TIM_OCPOLARITY_HIGH);
3 g0 y: V+ i$ l8 y } - " N B" E7 g- D9 w3 E; Y' ?" i; E
- LL_TIM_OC_SetCompareCH2(TIM2, SLOW_FREQ_PULSE);7 W- v2 U8 t4 f
-
4 I3 l" V" ?% n8 W# m1 O - LL_TIM_OC_EnablePreload(TIM2, PWM_CHANNEL);# B1 i( j& s/ Q% W; {
- $ [" M% x0 G/ j( Z5 V! u9 t. s2 Q
- LL_TIM_CC_EnableChannel(TIM2, PWM_CHANNEL);% J9 P- i, \& Y; _
- : @5 Q, {) t& N( B7 K$ g; T% V; O
- LL_TIM_GenerateEvent_UPDATE(TIM2);9 `2 l- s2 K3 `" F
- # g; d- n2 H# h. R
- LL_TIM_DisableCounter(TIM2);
复制代码 从定时器初始化- NVIC_SetPriority(TIM15_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),10, 0));
/ T5 ]9 X, u0 U7 P% e2 F" g - NVIC_EnableIRQ(TIM15_IRQn);
- y) p5 b- s9 z+ j& O n5 d - //从模式,连接到TIM2: u Q1 n2 Y9 ~9 O9 A0 ~
- LL_TIM_SetClockSource(TIM15,LL_TIM_CLOCKSOURCE_EXT_MODE1);
1 G; v4 S# b! B; O! Z4 ^- J) U# z - LL_TIM_EnableMasterSlaveMode(TIM15);
# U% b* l' J2 O9 B* s5 e - LL_TIM_SetTriggerInput(TIM15, LL_TIM_TS_ITR0);
* z% g; G6 N; ~! m! Q% q; A/ Y: n; L% v -
' h/ z9 X" G$ C( [$ A# @ - LL_TIM_SetClockDivision(TIM15, LL_TIM_CLOCKDIVISION_DIV1);
" e! o5 l1 ^2 [& W% V2 A - LL_TIM_SetCounterMode(TIM15, LL_TIM_COUNTERMODE_UP);
' j% X) ~2 R1 W0 }/ G) y2 s# S! j - LL_TIM_SetPrescaler(TIM15, 0);& u' K# N& R* E* _) W5 E X* r
- LL_TIM_SetAutoReload(TIM15, SLOW_PULSE_NUM);//第一组脉冲的数量+ r6 H5 w; M1 x" u
- LL_TIM_SetOnePulseMode(TIM15, LL_TIM_ONEPULSEMODE_SINGLE);
7 e- I! D0 d" q - LL_TIM_GenerateEvent_UPDATE(TIM15);
6 x1 _% _- B4 W5 f( ^% @# ^0 | - LL_TIM_DisableCounter(TIM15);
4 n4 Q$ A1 H }- g - LL_TIM_ClearFlag_UPDATE(TIM15);
1 |# {+ t. a; _' J; j# Z - LL_TIM_EnableIT_UPDATE(TIM15);
复制代码 4 L d9 d4 q* C% p& `
* o3 y2 h4 \( _) N2 i3 s! }$ a0 y6 Y8 E' T& Z1 W) C0 c" \
从定时器中断函数- void TIM1_BRK_TIM15_IRQHandler(void)9 b8 O/ h; A5 \. ~# s
- {
+ [% Q1 O8 w9 G5 r - if(LL_TIM_IsActiveFlag_UPDATE(TIM15))
" g8 p# c6 |5 r/ ]/ b - {
% J8 W/ `( N N# v9 l& d - LL_TIM_ClearFlag_UPDATE(TIM15);
1 P8 ]+ f$ A. s3 B, T: B3 @ - LL_TIM_OC_SetMode(TIM2, PWM_CHANNEL, LL_TIM_OCMODE_FORCED_INACTIVE);, N6 {& B9 Z9 A- i
- LL_TIM_DisableCounter(TIM2);- b7 T/ `5 e8 z* m' G/ q5 ~
- LL_TIM_SetAutoReload(TIM2, HIGH_FREQ_RELOAD);
- ?# v# u, p3 B; p1 E - LL_TIM_OC_SetCompareCH2(TIM2, HIGH_FREQ_PULSE);
6 o3 _) g% }; V - LL_TIM_SetCounter(TIM2, 0);
2 U' s$ G( s9 B5 Q/ J! z - LL_TIM_EnableCounter(TIM2);
n3 J+ Y$ Z' u h3 x9 p$ X - LL_TIM_OC_SetMode(TIM2, PWM_CHANNEL, LL_TIM_OCMODE_PWM2);) }' C. f# G3 ? u2 _7 J2 @) j
- }0 l G; z$ q% y2 V! Q) k) N
- }
复制代码 7 v! \8 j- x [/ }" U* b4 e- `
& y* j) W. _3 A& ?+ v
+ K! K) c% w! F启动定时器* x" p, o& J' ^/ H
- LL_TIM_EnableCounter(TIM15);
; Z# u$ p5 t) f$ o - LL_TIM_EnableCounter(TIM2);, X4 l9 @% \# \' m+ h
- LL_TIM_OC_SetMode(TIM2, PWM_CHANNEL, LL_TIM_OCMODE_PWM2);
复制代码 ) k' \6 [8 b$ L- y# `: {( n
1 u3 n0 i: {# z& z9 w2 G( `
- m. a: q8 \1 r Y
, `; E8 {7 u* F; `" x) R+ y( n4 _' w2 |
9 C+ u& E1 Y1 j2 e/ C9 ?
- m$ \- {8 P- {7 F, D" \( f
|