STM32G474分别使用CORDIC硬件和"math.h"的正弦值，从DAC1和DAC2输出。
1、DAC特点
PA4的附加功能为DAC1_OUT1，无需映射，直接将它配置为模拟功能，就可以使用了。
PA6的附加功能为DAC2_OUT1，无需映射，直接将它配置为模拟功能，就可以使用了。
2、测试程序
DAC_HandleTypeDef DAC_1_Handler; //DAC1句柄
DAC_HandleTypeDef DAC_2_Handler; //DAC2句柄
void DAC1_Init(void)
{
DAC_ChannelConfTypeDef DAC1_CH1; //DAC通道参数相关结构体
GPIO_InitTypeDef GPIO_InitStruct; //IO口参数结构体
__HAL_RCC_DAC1_CLK_ENABLE(); //使能DAC1时钟
__HAL_RCC_GPIOA_CLK_ENABLE(); //开启GPIOA时钟
GPIO_InitStruct.Pin = GPIO_PIN_4; //选择引脚编号为4
GPIO_InitStruct.Mode = GPIO_MODE_ANALOG; //模拟模式
GPIO_InitStruct.Pull = GPIO_NOPULL; //引脚上拉和下拉都没有被激活
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH; //输出速度设置为25MHz至50MHz
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
//根据GPIO_InitStruct结构变量指定的参数初始化GPIOC的外设寄存器
DAC_1_Handler.Instance = DAC1; //DAC1
HAL_DAC_Init(&DAC_1_Handler); //初始化DAC1
DAC1_CH1.DAC_HighFrequency = DAC_HIGH_FREQUENCY_INTERFACE_MODE_ABOVE_160MHZ;
//DAC时钟选择
DAC1_CH1.DAC_DMADoubleDataMode = DISABLE; //双重数据模式（高带宽模式）关闭
DAC1_CH1.DAC_SignedFormat = DISABLE; //有符号模式关闭
DAC1_CH1.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE; //关闭采样保持
DAC1_CH1.DAC_Trigger = DAC_TRIGGER_NONE; //不需要外部触发
DAC1_CH1.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE; //DAC输出缓冲器打开
DAC1_CH1.DAC_UserTrimming = DAC_TRIMMING_FACTORY; //工厂矫正模式
DAC1_CH1.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE; //不允许内部连接DAC1_CH1
HAL_DAC_ConfigChannel(&DAC_1_Handler, &DAC1_CH1, DAC_CHANNEL_1); //初始化
HAL_DACEx_SelfCalibrate(&DAC_1_Handler, &DAC1_CH1, DAC_CHANNEL_1); //矫正
HAL_DAC_Start(&DAC_1_Handler,DAC_CHANNEL_1); //开启DAC1通道1
HAL_DAC_SetValue(&DAC_1_Handler,DAC_CHANNEL_1,DAC_ALIGN_12B_R,2048);
//设置DAC输出电压: 2048*3.3/(0xFFF+1)=1.65V
Sin_CORDIC_INT();//用CORDIC算法实现正弦计算
}
void DAC2_Init(void)
{
DAC_ChannelConfTypeDef DAC2_CH1; //DAC通道参数相关结构体
GPIO_InitTypeDef GPIO_InitStruct; //IO口参数结构体
__HAL_RCC_DAC2_CLK_ENABLE(); //使能DAC2时钟
__HAL_RCC_GPIOA_CLK_ENABLE(); //开启GPIOA时钟
GPIO_InitStruct.Pin = GPIO_PIN_6; //选择引脚编号为6
GPIO_InitStruct.Mode = GPIO_MODE_ANALOG; //模拟模式
GPIO_InitStruct.Pull = GPIO_NOPULL; //引脚上拉和下拉都没有被激活
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH; //输出速度设置为25MHz至50MHz
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
//根据GPIO_InitStruct结构变量指定的参数初始化GPIOC的外设寄存器
DAC_2_Handler.Instance = DAC2; //DAC2
HAL_DAC_Init(&DAC_2_Handler); //初始化DAC2
DAC2_CH1.DAC_HighFrequency = DAC_HIGH_FREQUENCY_INTERFACE_MODE_ABOVE_160MHZ;
//DAC时钟选择
DAC2_CH1.DAC_DMADoubleDataMode = DISABLE; //双重数据模式（高带宽模式）关闭
DAC2_CH1.DAC_SignedFormat = DISABLE; //有符号模式关闭
DAC2_CH1.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE; //关闭采样保持
DAC2_CH1.DAC_Trigger = DAC_TRIGGER_NONE; //不需要外部触发
DAC2_CH1.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE; //DAC输出缓冲器打开
DAC2_CH1.DAC_UserTrimming = DAC_TRIMMING_FACTORY; //工厂矫正模式
DAC2_CH1.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE; //不允许内部连接DAC2_CH1
HAL_DAC_ConfigChannel(&DAC_2_Handler, &DAC2_CH1, DAC_CHANNEL_1); //初始化
HAL_DACEx_SelfCalibrate(&DAC_2_Handler, &DAC2_CH1, DAC_CHANNEL_1); //矫正
HAL_DAC_Start(&DAC_2_Handler,DAC_CHANNEL_1); //开启DAC2通道1
HAL_DAC_SetValue(&DAC_2_Handler,DAC_CHANNEL_1,DAC_ALIGN_12B_R,2048);
//设置DAC2输出电压: 2048*3.3/(0xFFF+1)=1.65V
}
//函数功能: 用CORDIC算法实现正弦计算
void Sin_CORDIC_INT (void)
{
CORDIC_HandleTypeDef hcordic; //三角函数描述结构体
CORDIC_ConfigTypeDef sCordicConfig; //参数配置结构体
__HAL_RCC_CORDIC_CLK_ENABLE(); //开启时钟
hcordic.Instance = CORDIC; //选择三角函数计算单元
HAL_CORDIC_Init(&hcordic); //初始化
sCordicConfig.Function = CORDIC_FUNCTION_SINE; //选择计算正弦
sCordicConfig.Precision = CORDIC_PRECISION_6CYCLES; //选择计算精度等级
sCordicConfig.Scale = CORDIC_SCALE_0; //选择计算系数
sCordicConfig.NbWrite = CORDIC_NBWRITE_1; //选择计算结果个数
sCordicConfig.NbRead = CORDIC_NBREAD_1; //选择输出正弦
sCordicConfig.InSize = CORDIC_INSIZE_32BITS;
//选择输入数据格式Q1.31，在Q1.31格式的数字范围：-1 (0x80000000) to 1 至 2^(-31) (0x7FFFFFFF).
sCordicConfig.OutSize = CORDIC_OUTSIZE_32BITS; //选择数据输出格式Q1.31
HAL_CORDIC_Configure(&hcordic, &sCordicConfig); //初始化
}
//0<=angles<360,返回值在-1和1之间
//主频170MHz时，本函数执行时间330ns
float sin_f(float angles)
{
MODIFY_REG(CORDIC->CSR,CORDIC_CSR_FUNC|CORDIC_CSR_SCALE,CORDIC_FUNCTION_SINE|CORDIC_SCALE_0);
//选择计算类型:CORDIC_FUNCTION_SINE
WRITE_REG(CORDIC->WDATA, (int32_t)((180.0f-angles)*11930464.7f));
//小于180度为正数，大于180度为负数，乘以11930464.7就转换成"q1.31格式"的数据
//写入CORDIC_WDATA寄存器后，就可以读取"CORDIC_RDATA寄存器的数据"
//由于"模为0x80000000"，0x80000000/180=2147483648/180=11930464.7
return (int32_t)READ_REG(CORDIC->RDATA)/2147483648.0f;
//读取CORDIC_RDATA寄存器的数据是"q1.31格式"的数据，经过转换后，就是正弦值
//由于"模为0x80000000"，也就是2147483648，除以"模"后就得到正弦值，范围为[-1,1]
}
//函数功能：测试DAC输出正弦波形
void Test_DAC_Output_CORDIC_Sin(void)
{
__IO float i=0.0f;
__IO uint16_t ADC_value1=0x00;
while(1)
{
for(i=0.0f;i<360.0f;i=i+0.1f)
{
ADC_value1=((sin_f(i)+1.65f)/3.3f)*4095.0f;
//使用硬件实现，需要3.72ms完成一个for循环
//设置偏置电压为1.65V,当sin_f(i)=0，ADC的值为1.65V
HAL_DAC_SetValue(&DAC_1_Handler,DAC_CHANNEL_1,DAC_ALIGN_12B_R,ADC_value1);
//设置DAC输出电压: ADC_value1 * 3.3 / (0xFFF+1),单位为"V"
}
}
}
//函数功能：测试DAC输出正弦波形
void Test_DAC_Output_math_Sin(void)
{
__IO float i=0.0f;
__IO uint16_t ADC_value1=0x00;
while(1)
{
for(i=0.0f;i<360.0f;i=i+0.1f)
{
ADC_value1=( ( sin(i*3.1415926/180)+1.65f )/3.3f )*4095.0f;
//使用数学函数，需要172ms完成一个for循环
HAL_DAC_SetValue(&DAC_2_Handler,DAC_CHANNEL_1,DAC_ALIGN_12B_R,ADC_value1);
//设置DAC输出电压: ADC_value1 * 3.3 / (0xFFF+1),单位为"V"
}
}
}
3、测试结果
在没有任何延时的条件下，硬件产生正弦波形周期比软件产生正弦波形要小很多。，说明硬件响应速度比软件快。