)实现波形的产生。利用stm32f103单片机生成一个频率为 4-5KBz占空比为50%，峰峰值为 3.3v的方波，频率可以通过按键直接调整及步进可调，步进小于等于1Hz。和频率为12-15KHz峰峰值为2.2v的正弦波，频率可以通过按键直接调整及步进可调，步进小于等于16Hz。

要实现波形的产生，需要使用STM32F103单片机的定时器和DAC模块。具体步骤如下：

1. 初始化定时器和DAC模块，使它们可以工作。

2. 在定时器中断中产生方波和正弦波的数据，并将数据写入DAC寄存器。

3. 根据按键输入来调整方波和正弦波的频率，步进大小可以根据需求设置。

下面是示例代码，仅供参考：

#include "stm32f10x.h"

#define PI 3.1415926

uint16_t sinData[256] = { //正弦波数据
  2048, 2148, 2248, 2348, 2447, 2546, 2644, 2741, 
  2837, 2932, 3025, 3117, 3207, 3295, 3381, 3465, 
  3546, 3625, 3701, 3775, 3845, 3912, 3976, 4036, 
  4093, 4146, 4195, 4239, 4279, 4314, 4345, 4370, 
  4389, 4403, 4410, 4410, 4403, 4389, 4370, 4345, 
  4314, 4279, 4239, 4195, 4146, 4093, 4036, 3976, 
  3912, 3845, 3775, 3701, 3625, 3546, 3465, 3381, 
  3295, 3207, 3117, 3025, 2932, 2837, 2741, 2644, 
  2546, 2447, 2348, 2248, 2148, 2048, 1948, 1848, 
  1748, 1649, 1550, 1452, 1355, 1260, 1167, 1075, 
  987, 899, 814, 730, 649, 571, 495, 422, 
  352, 286, 223, 163, 107, 54, 6, 0, 
  48, 92, 131, 165, 193, 216, 232, 242, 
  246, 242, 232, 216, 193, 165, 131, 92, 
  48, 0, 6, 54, 107, 163, 223, 286, 
  352, 422, 495, 571, 649, 730, 814, 899, 
  987, 1075, 1167, 1260, 1355, 1452, 1550, 1649, 
  1748, 1848, 1948
};

uint16_t sinIndex = 0; //正弦波数据索引
uint32_t sinStep = 0; //正弦波步进值

uint16_t freq = 5000; //方波频率
uint16_t duty = 50; //方波占空比

void TIM2_IRQHandler(void)
{
  static uint16_t count = 0;
  static uint8_t dir = 0; //方波计数方向

  if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET) {
    TIM_ClearITPendingBit(TIM2, TIM_IT_Update);

    //计算方波数据
    if (count == 0) {
      dir = 0;
    }
    else if (count == (100 - duty) * 2) {
      dir = 1;
    }
    if (dir == 0) {
      DAC_SetChannel1Data(DAC_Align_12b_R, 4095);
    }
    else {
      DAC_SetChannel1Data(DAC_Align_12b_R, 0);
    }
    count = (count + 1) % 200;

    //计算正弦波数据
    sinStep += (uint32_t)(sinIndex * freq);
    DAC_SetChannel2Data(DAC_Align_12b_R, sinData[sinIndex]);
    sinIndex = (sinStep >> 16) & 0xFF;
  }
}

int main(void)
{
  TIM_TimeBaseInitTypeDef tim;
  TIM_OCInitTypeDef oc;
  DAC_InitTypeDef dac;
  GPIO_InitTypeDef gpio;

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);

  //初始化TIM2
  tim.TIM_Period = (SystemCoreClock / freq) - 1;
  tim.TIM_Prescaler = 0;
  tim.TIM_ClockDivision = TIM_CKD_DIV1;
  tim.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM2, &tim);

  //初始化DAC
  dac.DAC_Trigger = DAC_Trigger_T2_TRGO;
  dac.DAC_WaveGeneration = DAC_WaveGeneration_None;
  dac.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
  DAC_Init(DAC_Channel_1, &dac);
  DAC_Init(DAC_Channel_2, &dac);

  //初始化GPIO
  gpio.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5;
  gpio.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOA, &gpio);

  gpio.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
  gpio.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOA, &gpio);

  //配置TIM2输出比较通道1和2
  oc.TIM_OCMode = TIM_OCMode_PWM1;
  oc.TIM_OutputState = TIM_OutputState_Enable;
  oc.TIM_Pulse = ((SystemCoreClock / freq) * duty / 100) - 1;
  oc.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OC1Init(TIM2, &oc);
  TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);
  TIM_OC2Init(TIM2, &oc);
  TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable);

  //启用TIM2中断
  TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
  NVIC_EnableIRQ(TIM2_IRQn);

  //启动TIM2和DAC
  TIM_Cmd(TIM2, ENABLE);
  DAC_Cmd(DAC_Channel_1, ENABLE);
  DAC_Cmd(DAC_Channel_2, ENABLE);

  while (1) {
    //根据按键调整方波频率和占空比
    if (!GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_4)) {
      freq += 1;
      tim.TIM_Period = (SystemCoreClock / freq) - 1;
      TIM_TimeBaseInit(TIM2, &tim);
    }
    if (!GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_5)) {
      freq -= 1;
      tim.TIM_Period = (SystemCoreClock / freq) - 1;
      TIM_TimeBaseInit(TIM2, &tim);
    }
    if (!GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_6)) {
      duty += 5;
      oc.TIM_Pulse = ((SystemCoreClock / freq) * duty / 100) - 1;
      TIM_OC1Init(TIM2, &oc);
    }
    if (!GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_7)) {
      duty -= 5;
      oc.TIM_Pulse = ((SystemCoreClock / freq) * duty / 100) - 1;
      TIM_OC1Init(TIM2, &oc);
    }
    //根据按键调整正弦波频率
    if (!GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_8)) {
      sinStep = 0;
      sinIndex = 0;
      freq += 16;
    }
    if (!GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_9)) {
      sinStep = 0;
      sinIndex = 0;
      freq -= 16;
    }
  }
}

需要注意的是，方波和正弦波的频率和占空比的计算都需要根据系统时钟频率进行调整，以保证输出的波形符合要求。同时，DAC的输出电压也需要根据具体情况进行调整，以避免超过芯片的最大输出电压。