用C++语言，编写一段stm32单片机使用的程序，实现应变片阻值变化进行计数，并输出阻值，用LED屏显示阻值，用WiFi模块输出计数值

下面是一份示例代码，可以实现stm32单片机使用应变片检测阻值变化，通过LED屏显示阻值，通过WiFi模块输出计数值：

#include <WiFi.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_LEDBackpack.h>

#define LED_DISPLAY_ADDRESS 0x70

Adafruit_7segment led = Adafruit_7segment();

const char* ssid = "YourSSID";
const char* password = "YourPassword";
const char* mqtt_server = "mqtt_server_address";
const char* mqtt_username = "mqtt_username";
const char* mqtt_password = "mqtt_password";

WiFiClient espClient;
PubSubClient client(espClient);

const int strain_gauge_pin = A0;
const int led_pin = 13;

int count = 0;
int last_reading = 0;

void setup_wifi() {
  delay(10);
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void reconnect() {
  while (!client.connected()) {
    Serial.print("Connecting to MQTT broker...");
    if (client.connect("ESP32Client", mqtt_username, mqtt_password )) {
      Serial.println("connected");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(strain_gauge_pin, INPUT);
  pinMode(led_pin, OUTPUT);

  led.begin(LED_DISPLAY_ADDRESS);
  led.clear();
  led.writeDisplay();

  setup_wifi();
  client.setServer(mqtt_server, 1883);
}

void loop() {
  int reading = analogRead(strain_gauge_pin);
  if (reading != last_reading) {
    count++;
    last_reading = reading;
    led.print(reading);
    led.writeDisplay();
  }

  if (!client.connected()) {
    reconnect();
  }
  client.loop();

  char message[50];
  sprintf(message, "Count: %d", count);
  client.publish("strain_gauge", message);
}

本代码使用WiFi模块连接到MQTT服务器，并将每次检测到应变片阻值变化后的计数值发布到MQTT主题“strain_gauge”中。同时，使用LED屏显示当前应变片的阻值。您需要根据您的具体硬件和网络环境对代码进行适当的修改。