silly pid:113107781 by:paccha!!

DAC (Digital to Analog Converter, 数模转换器)

DAC 基础部分

The function of a DAC is to convert digital signals into analog signals. The working principle of a DAC is the opposite of that of an ADC. A DAC can convert digital signals into analog signals for output and control.

DACs have a wide range of applications in daily life, such as digital signal processing, mobile phones, MCU power supplies, audio amplifiers, etc.

A typical DAC module is shown in the figure below:

It includes pins for digital signal input, several control lines, an external reference voltage input, and the final voltage output.

For a typical DAC, the formula for its output voltage is as follows:

• Output voltage
• Digital input value
• DAC bit depth
• Reference voltage

From this, we can derive that the output range of the DAC is , and its resolution is

DAC in MBed OS

For the <span>NUCLEO-L432KC</span> development board we are using, it has 2 channels of DAC output, with the reference voltage and input voltage being the same at <span>3.3V</span>. In our experimental <span>MBed OS</span> environment, the DAC should be used as follows:

// Defines a DAC output object connected to pin A6
AnalogOut dac_out(A6);
// Sets the DAC output to 0.5 * Vref
dac_out = 0.5;

Similar to ADC, the value written to the DAC here is also a floating-point number, ranging from 0 to 1. Below are the specific methods of the <span>AnalogOut</span> class.

• <span>AnalogOut(PinName pin)</span>
• Constructor that initializes the DAC output object and connects it to the specified pin.
• <span>void write(float val)</span>
• Writes a floating-point value to the DAC output, ranging from 0 to 1.
• <span>void write_u16(uint16_t val)</span>
• Writes a 16-bit unsigned integer value to the DAC output, ranging from 0 to 65535.
• <span>void operator=(float val)</span>
• Equivalent to the <span>write</span> method, ranging from 0 to 1.