C++如何查询回调之外的值arduino

Question

我希望BLE可以从手机更改测量间隔和MQTT服务器设置。我使用LightBlue作为移动应用程序。

这是我的BLE代码，与我的移动应用程序配合良好

#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>
#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
std::string value = pCharacteristic->getValue();
if (value.length() > 0) {
Serial.println("*********");
Serial.print("New value: ");
for (int i = 0; i < value.length(); i++)
Serial.print(value[i]);
Serial.println();
Serial.println("*********");
}
}
};
void setup() {
Serial.begin(115200);
Serial.println("1- Download and install an BLE scanner app in your phone");
Serial.println("2- Scan for BLE devices in the app");
Serial.println("3- Connect to MyESP32");
Serial.println("4- Go to CUSTOM CHARACTERISTIC in CUSTOM SERVICE and write something");
Serial.println("5- See the magic =)");
BLEDevice::init("MyESP32");
BLEServer *pServer = BLEDevice::createServer();
BLEService *pService = pServer->createService(SERVICE_UUID);
BLECharacteristic *pCharacteristic = pService->createCharacteristic(
CHARACTERISTIC_UUID,
BLECharacteristic::PROPERTY_READ |
BLECharacteristic::PROPERTY_WRITE
);
pCharacteristic->setCallbacks(new MyCallbacks());
pCharacteristic->setValue("Hello World");
pService->start();
BLEAdvertising *pAdvertising = pServer->getAdvertising();
pAdvertising->start();
}
void loop() {
// put your main code here, to run repeatedly:
delay(2000);
}

这是MQTT代码：

void loop() {
unsigned long currentMillis = millis();
// Every X number of seconds (interval = 10 seconds) 
// it publishes a new MQTT message
if (currentMillis - previousMillis >= interval) {
// Save the last time a new reading was published
previousMillis = currentMillis;
// New DHT sensor readings
hum = dht.readHumidity();
// Read temperature as Celsius (the default)
temp = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
//temp = dht.readTemperature(true);    
// Check if any reads failed and exit early (to try again).
if (isnan(temp) || isnan(hum)) {
Serial.println(F("Failed to read from DHT sensor!"));
return;
}

// Publish an MQTT message on topic esp32/dht/temperature
uint16_t packetIdPub1 = mqttClient.publish(MQTT_PUB_TEMP, 1, true, String(temp).c_str());                            
Serial.printf("Publishing on topic %s at QoS 1, packetId: %i", MQTT_PUB_TEMP, packetIdPub1);
Serial.printf("Message: %.2f n", temp);
// Publish an MQTT message on topic esp32/dht/humidity
uint16_t packetIdPub2 = mqttClient.publish(MQTT_PUB_HUM, 1, true, String(hum).c_str());                            
Serial.printf("Publishing on topic %s at QoS 1, packetId %i: ", MQTT_PUB_HUM, packetIdPub2);
Serial.printf("Message: %.2f n", hum);
}
}

请告诉我如何将间隔设置为BLE代码中的任何变量，而不是10000。

long interval = 10000;

Answer 1

您需要将变量interval声明为全局变量，以便从文件中的任何位置访问它。全局变量可以在函数之外声明。

您收到的值的类型是std:：string，并且您希望使用它的长度。您可以使用toInt((将变量从String转换为Long。

试试这样的东西：

long interval = 10000; // Set default value
class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
std::string value = pCharacteristic->getValue();
if (value.length() > 0) {
Serial.println("*********");
Serial.print("New value: ");
for (int i = 0; i < value.length(); i++)
Serial.print(value[i]);
Serial.println();
Serial.println("*********");
interval = value.toInt(); // <-- Set received value
}
}
};