利用stm32f103zet6单片机同时生成一个频率为 4-5KHz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。生成keil5代码

以下是基于你的要求，给出的一个简单的实现，仅供参考：

#include "stm32f10x.h"

#define PI 3.14159265358979323846f
#define SAMPLE_SIZE 256

volatile uint16_t sine_data[SAMPLE_SIZE];

volatile uint32_t freq1 = 5000;  // 方波频率，默认为5KHz
volatile uint32_t freq2 = 12000; // 正弦波频率，默认为12KHz

volatile uint8_t step1 = 1;  // 方波频率步进值，默认为1Hz
volatile uint8_t step2 = 16; // 正弦波频率步进值，默认为16Hz

volatile uint16_t cnt1 = 0;    // 方波计数器
volatile uint16_t cnt2 = 0;    // 正弦波计数器
volatile uint16_t sin_index = 0; // 正弦波数据表索引

void TIM1_UP_IRQHandler(void) // 定时器中断处理函数
{
    if (TIM_GetITStatus(TIM1, TIM_IT_Update) != RESET)
    {
        TIM_ClearITPendingBit(TIM1, TIM_IT_Update);

        cnt1++;
        if (cnt1 > 999) // 方波计数器超过计数范围，重置计数器
        {
            cnt1 = 0;
        }

        if (cnt1 < 500) // 占空比为50%
        {
            GPIO_SetBits(GPIOA, GPIO_Pin_0); // 输出高电平
        }
        else
        {
            GPIO_ResetBits(GPIOA, GPIO_Pin_0); // 输出低电平
        }

        cnt2++;
        if (cnt2 > freq1) // 正弦波计数器超过设定频率，重置计数器
        {
            cnt2 = 0;
            sin_index += step2; // 修改正弦波数据表索引
            if (sin_index >= SAMPLE_SIZE)
            {
                sin_index -= SAMPLE_SIZE;
            }
        }

        DAC_SetChannel1Data(DAC_Align_12b_R, sine_data[sin_index]); // 输出正弦波数据
    }
}

void generate_sine_data(void) // 生成正弦波数据表
{
    uint16_t i;
    for (i = 0; i < SAMPLE_SIZE; i++)
    {
        sine_data[i] = (uint16_t)(2048.0f + 2047.0f * sin(2.0f * PI * i / SAMPLE_SIZE));
    }
}

int main(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    DAC_InitTypeDef DAC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2 | RCC_APB1Periph_TIM3 | RCC_APB1Periph_DAC, ENABLE);

    // 初始化GPIO
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // 初始化定时器1
    TIM_TimeBaseStructure.TIM_Period = 999;
    TIM_TimeBaseStructure.TIM_Prescaler = 71;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

    TIM_OCInitTypeDef TIM_OCInitStructure;
    TIM_OCStructInit(&TIM_OCInitStructure);
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 499; // 占空比为50%
    TIM_OC1Init(TIM1, &TIM_OCInitStructure);
    TIM_Cmd(TIM1, ENABLE);

    // 初始化定时器2
    TIM_TimeBaseStructure.TIM_Period = 999;
    TIM_TimeBaseStructure.TIM_Prescaler = 71;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM2, ENABLE);

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

    // 初始化中断控制器
    NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    generate_sine_data(); // 生成正弦波数据表

    while (1)
    {
        // 检测频率调整按键
        if (GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_13) == RESET)
        {
            freq1 += step1; // 修改方波频率
            if (freq1 > 5000)
            {
                freq1 = 4000;
            }
        }

        if (GPIO_ReadInputDataBit(GPIOC, GPIO_Pin_14) == RESET)
        {
            freq2 += step2; // 修改正弦波频率
            if (freq2 > 15000)
            {
                freq2 = 12000;
            }
        }

        // 延时一段时间
        uint32_t delay = 100000;
        while (delay--)
            ;
    }
}

需要注意的是，以上代码仅为参考，实际应用中需要根据具体情况进行修改和完善。