解释代码#define voltage_normal （1）

这行代码定义了一个名为 "voltage_normal" 的预处理宏，其值被设置为 1。在代码中，可以使用 "voltage_normal" 来代替 1，从而使代码更加易读易维护。例如，可以使用以下代码段来检查电压是否正常：

if (voltage > voltage_normal) {
    // 处理电压异常情况
}

这将比以下代码更加易读：

if (voltage > 1) {
    // 处理电压异常情况
}

因为读者可能不知道数字 1 的含义是什么。因此，使用预定义的宏可以使代码更加易读易懂。

相关问题

驱动AD5420的代码

AD5420是一款4-20mA电流输出型数字-模拟转换器（DAC），以下是一个基于Arduino的AD5420驱动代码示例：

#include <SPI.h>

// 定义AD5420的寄存器地址
#define AD5420_REG_CTRL  0x0000
#define AD5420_REG_HI    0x0001
#define AD5420_REG_LO    0x0002

// 定义SPI通信引脚
#define AD5420_CS_PIN    10

// 定义AD5420的控制字
#define AD5420_CTRL_POWDOWN  0x0004  // 掉电模式，输出为0mA
#define AD5420_CTRL_NORMAL   0x0000  // 正常模式，输出为4mA-20mA
#define AD5420_CTRL_EXT_REF  0x0002  // 使用外部参考电压
#define AD5420_CTRL_INT_REF  0x0000  // 使用内部参考电压

// 定义参考电压
#define AD5420_REF_VOLTAGE  5.0

// 初始化SPI
void setupSPI() {
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV16);
  SPI.setDataMode(SPI_MODE2);
}

// 向AD5420写入数据
void writeAD5420(uint16_t reg, uint16_t data) {
  digitalWrite(AD5420_CS_PIN, LOW);  // 选中AD5420
  SPI.transfer16(reg);               // 发送寄存器地址
  SPI.transfer16(data);              // 发送数据
  digitalWrite(AD5420_CS_PIN, HIGH); // 取消选中AD5420
}

// 将电压转换为DAC码
uint16_t voltageToDAC(float voltage) {
  uint16_t dac_code = voltage / AD5420_REF_VOLTAGE * 65535;
  return dac_code;
}

// 设置输出电流
void setOutputCurrent(float current) {
  uint16_t dac_code = voltageToDAC(current * 0.001 + 4);  // 计算DAC码
  writeAD5420(AD5420_REG_HI, dac_code >> 8);              // 写入高8位
  writeAD5420(AD5420_REG_LO, dac_code & 0xFF);            // 写入低8位
}

void setup() {
  pinMode(AD5420_CS_PIN, OUTPUT);
  digitalWrite(AD5420_CS_PIN, HIGH);
  setupSPI();
  writeAD5420(AD5420_REG_CTRL, AD5420_CTRL_NORMAL | AD5420_CTRL_INT_REF);  // 初始化控制字
}

void loop() {
  setOutputCurrent(12.34);  // 设置输出电流为12.34mA
  delay(1000);
}

这个代码示例使用了Arduino的SPI库来驱动AD5420，通过SPI协议向其写入控制字和数据。在`setOutputCurrent`函数中，我们将要输出的电流转换为DAC码，然后将其写入到AD5420的寄存器中。

There is a light sensor on your picoprobe development board. This question asks you to use this sensor to measure the ambient light and to control the three LEDs on the picoprobe board to make a night light. Configure your program to perform the following steps, after printing the message from Question 1. The steps should be repeated every 1 second. raw ADC result in the format shown below: Light Sensor: Raw: _____ (insert the actual value) (15 marks) (b) Convert the raw value to a voltage and print out the voltage that you calculated in the format displayed below. At least one decimal place is required. Voltage: _____ V (insert the actual value) (10 marks) (c) Use this voltage to control the three-colour LED to show a white colour, when the light sensor is covered by a piece of paper (e.g. when the room is getting dark). The white-coloured light will go off, as soon as the ambient light is high again, i.e. when the light sensor is exposed to normal room light. This is reminiscent of an automatic night light.

Sure, here's how you can use the light sensor on the picoprobe development board to create a night light:

(a)
1. Initialize the ADC to read from the light sensor.
2. Read the raw ADC value from the light sensor.
3. Print out the raw ADC value in the format "Light Sensor: Raw: [value]".
4. Convert the raw ADC value to a voltage using the formula: voltage = (raw_value * 3.3) / 4095, where 3.3 is the maximum voltage and 4095 is the maximum raw ADC value.
5. Print out the voltage value in the format "Voltage: [value] V".
6. Use the voltage value to control the three-colour LED.

(b)
Here's some sample code to perform the above steps:

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/adc.h"
#include "hardware/gpio.h"

#define LED_RED 25
#define LED_GREEN 26
#define LED_BLUE 27
#define LIGHT_SENSOR 2

int main() {
    stdio_init_all();
    adc_init();
    adc_gpio_init(LIGHT_SENSOR);
    adc_select_input(LIGHT_SENSOR);

    gpio_init(LED_RED);
    gpio_set_dir(LED_RED, GPIO_OUT);
    gpio_init(LED_GREEN);
    gpio_set_dir(LED_GREEN, GPIO_OUT);
    gpio_init(LED_BLUE);
    gpio_set_dir(LED_BLUE, GPIO_OUT);

    while (1) {
        uint16_t raw_value = adc_read();
        printf("Light Sensor: Raw: %d\n", raw_value);
        float voltage = (raw_value * 3.3) / 4095;
        printf("Voltage: %.1f V\n", voltage);

        if (voltage < 1.0) {  // dim the LEDs when the room is dark
            gpio_put(LED_RED, 255);
            gpio_put(LED_GREEN, 255);
            gpio_put(LED_BLUE, 255);
        } else {  // turn off the LEDs when there is enough ambient light
            gpio_put(LED_RED, 0);
            gpio_put(LED_GREEN, 0);
            gpio_put(LED_BLUE, 0);
        }

        sleep_ms(1000);
    }

    return 0;
}

(c)
In the above code, we are dimming all three LEDs to create white light when the room is dark and turning them off when there is enough ambient light. The threshold voltage for detecting darkness is set at 1.0 V in this example, but you can adjust it to suit your needs.