SHT30/SHT40 温湿度传感器 STM32F103 接线与代码

#include <Arduino.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Wire.h>

constexpr uint8_t OLED_ADDR = 0x3C;
constexpr int SCREEN_WIDTH = 128;
constexpr int SCREEN_HEIGHT = 64;

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

enum ShtType : uint8_t { SHT_NONE = 0, SHT30, SHT40 };

// Sensirion CRC-8, polynomial 0x31, init 0xFF.
static bool shtCrcOk(const uint8_t *data, uint8_t len, uint8_t crc) {
  uint8_t c = 0xFF;
  for (uint8_t i = 0; i < len; i++) {
    c ^= data[i];
    for (uint8_t b = 0; b < 8; b++) {
      c = (c & 0x80) ? (uint8_t)((c << 1) ^ 0x31) : (uint8_t)(c << 1);
    }
  }
  return c == crc;
}

// Read one temperature + humidity sample from an SHT30 or SHT40.
bool shtRead(uint8_t addr, ShtType type, float &temp, float &rh) {
  // SHT30: 0x2C06 = single shot, high repeatability, clock stretching.
  // SHT40: 0xFD   = high precision T & RH.
  uint16_t cmd = (type == SHT40) ? 0xFD : 0x2C06;
  float rhOffset = (type == SHT40) ? -6.0f : 0.0f;
  float rhScale = (type == SHT40) ? 125.0f : 100.0f;

  Wire.beginTransmission(addr);
  Wire.write((uint8_t)(cmd >> 8));
  Wire.write((uint8_t)(cmd & 0xFF));
  if (Wire.endTransmission() != 0) {
    return false;
  }

  // SHT40 has no clock stretching on the measure command: wait for it.
  // For SHT30 this wait is harmless (0x2C06 stretches the clock anyway).
  delay(10);

  uint8_t buf[6] = {0};
  if (Wire.requestFrom(addr, (uint8_t)6) < 6) {
    return false;
  }
  for (uint8_t i = 0; i < 6; i++) {
    buf[i] = (uint8_t)Wire.read();
  }

  // 6 bytes: T_MSB, T_LSB, T_CRC, RH_MSB, RH_LSB, RH_CRC.
  if (!shtCrcOk(buf, 2, buf[2]) || !shtCrcOk(buf + 3, 2, buf[5])) {
    return false;
  }

  uint16_t st = (uint16_t)((buf[0] << 8) | buf[1]);
  uint16_t sr = (uint16_t)((buf[3] << 8) | buf[4]);

  temp = -45.0f + 175.0f * (float)st / 65535.0f;
  rh = rhOffset + rhScale * (float)sr / 65535.0f;
  return true;
}

void showStatus(const char *line1, const char *line2) {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("02_SHT30_SHT40");
  display.println();
  display.println(line1);
  display.println(line2);
  display.display();
}

void showReadout(const char *name, uint8_t addr, float temp, float rh) {
  char buf[24];
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);

  display.setCursor(0, 0);
  display.print("02_SHT30_SHT40");

  display.setCursor(0, 16);
  snprintf(buf, sizeof(buf), "%s @0x%02X", name, addr);
  display.print(buf);

  display.setCursor(0, 32);
  snprintf(buf, sizeof(buf), "T: %.1f C", temp);
  display.print(buf);

  display.setCursor(0, 48);
  snprintf(buf, sizeof(buf), "RH: %.1f %%", rh);
  display.print(buf);

  display.display();
}

uint8_t g_shtAddr = 0;
ShtType g_shtType = SHT_NONE;

void detectSht() {
  float t = 0.0f, rh = 0.0f;
  // 0x44/0x45 是 SHT30 的 ADDR 引脚两种接法；0x46 是 SHT40-BD1B 出厂固定地址，
  // 漏掉 0x46 会让那个型号报"找不到传感器"，被误判成坏件
  for (uint8_t addr : {0x44, 0x45, 0x46}) {
    if (shtRead(addr, SHT40, t, rh)) {
      g_shtAddr = addr;
      g_shtType = SHT40;
      return;
    }
    if (shtRead(addr, SHT30, t, rh)) {
      g_shtAddr = addr;
      g_shtType = SHT30;
      return;
    }
  }
  g_shtAddr = 0;
  g_shtType = SHT_NONE;
}

void setup() {
  Serial.begin(115200);
  delay(300);

  Wire.setSCL(PB8);
  Wire.setSDA(PB9);
  Wire.begin();

  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR)) {
    Serial.println("OLED init failed");
    while (true) {
      delay(1000);
    }
  }

  showStatus("OLED OK", "SHT detect...");
  Serial.println("OLED OK");
  detectSht();
}

void loop() {
  if (g_shtType == SHT_NONE) {
    detectSht();
  }

  if (g_shtType == SHT_NONE) {
    showStatus("SHT not found", "Check wiring");
    Serial.println("SHT30/SHT40 not found");
  } else {
    float temp = 0.0f, rh = 0.0f;
    const char *name = (g_shtType == SHT40) ? "SHT40" : "SHT30";
    if (shtRead(g_shtAddr, g_shtType, temp, rh)) {
      char buf[48];
      snprintf(buf, sizeof(buf), "%s T=%.2f C RH=%.2f %%", name, temp, rh);
      showReadout(name, g_shtAddr, temp, rh);
      Serial.println(buf);
    } else {
      showStatus("Read failed", "Check wiring");
      Serial.println("SHT read failed");
    }
  }

  delay(1000);
}