esp32 cam PubSubClient 不发布 base64 编码的消息

Question

我正在尝试使用 esp32 cam 捕获图像并将其发送到 AWS IoT Core 以在云中对该图像进行进一步处理。

图像被捕获并编码为 base64 但是当我调用发布函数时它没有发送数据

void capture(){
  camera_fb_t *fb = esp_camera_fb_get();
  if(!fb){
      Serial.println("capture failed");
  }
  String encoded = base64::encode(fb->buf, fb->len);
  boolean r = client.publish("srp",encoded.c_str());
  if(r){
    Serial.println("sent");
  }
  else{
    Serial.println("Not sent");
  }
  delay(10000);
}

整体代码：

#include "esp_camera.h"
#include "Arduino.h"
#include "WiFi.h"
#include "SPIFFS.h"
#include "esp_timer.h"
#include "img_converters.h"
#include <WiFiClientSecure.h>
#include <PubSubClient.h>
#include <base64.h>
#include "soc/soc.h" // Disable brownour problems
#include "soc/rtc_cntl_reg.h" // Disable brownour problems
#include "driver/rtc_io.h"
#include <EEPROM.h>
#define CAMERA_MODEL_AI_THINKER // Has PSRAM

#include "camera_pins.h";

#define FLASH_GPIO_NUM 4

#define BUFFER_LEN 256
#define EEPROM_SIZE 1
#define PWDN_GPIO_NUM 32
#define RESET_GPIO_NUM -1
#define XCLK_GPIO_NUM 0
#define SIOD_GPIO_NUM 26
#define SIOC_GPIO_NUM 27
#define Y9_GPIO_NUM 35
#define Y8_GPIO_NUM 34
#define Y7_GPIO_NUM 39
#define Y6_GPIO_NUM 36
#define Y5_GPIO_NUM 21
#define Y4_GPIO_NUM 19
#define Y3_GPIO_NUM 18
#define Y2_GPIO_NUM 5
#define VSYNC_GPIO_NUM 25
#define HREF_GPIO_NUM 23
#define PCLK_GPIO_NUM 22
#define FLASH_GPIO_NUM 4

const char* ssid = "--------"; //Provide your SSID
const char* password = "-------"; // Provide Password
const char* mqtt_server = "afaamjzdbbphc-ats.iot.us-east-1.amazonaws.com"; // Relace with your MQTT END point
const int   mqtt_port = 8883;

String Read_rootca;
String Read_cert;
String Read_privatekey;
long lastMsg = 0;
char msg[BUFFER_LEN];
int Value = 0;
byte mac[6];
char mac_Id[18];
int count = 1;


WiFiClientSecure espClient;
PubSubClient client(espClient);

void initCam() {

  WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0);
  
  camera_config_t config;
  config.ledc_channel = LEDC_CHANNEL_0;
  config.ledc_timer = LEDC_TIMER_0;
  config.pin_d0 = Y2_GPIO_NUM;
  config.pin_d1 = Y3_GPIO_NUM;
  config.pin_d2 = Y4_GPIO_NUM;
  config.pin_d3 = Y5_GPIO_NUM;
  config.pin_d4 = Y6_GPIO_NUM;
  config.pin_d5 = Y7_GPIO_NUM;
  config.pin_d6 = Y8_GPIO_NUM;
  config.pin_d7 = Y9_GPIO_NUM;
  config.pin_xclk = XCLK_GPIO_NUM;
  config.pin_pclk = PCLK_GPIO_NUM;
  config.pin_vsync = VSYNC_GPIO_NUM;
  config.pin_href = HREF_GPIO_NUM;
  config.pin_sscb_sda = SIOD_GPIO_NUM;
  config.pin_sscb_scl = SIOC_GPIO_NUM;
  config.pin_pwdn = PWDN_GPIO_NUM;
  config.pin_reset = RESET_GPIO_NUM;
  config.xclk_freq_hz = 20000000;
  config.pixel_format = PIXFORMAT_JPEG;
  //init with high specs to pre-allocate larger buffers
  if(psramFound()){
    config.frame_size = FRAMESIZE_QVGA;
    config.jpeg_quality = 10;
    config.fb_count = 2;
  } else {
    config.frame_size = FRAMESIZE_QVGA;
    config.jpeg_quality = 12;
    config.fb_count = 1;
  }

  #if defined(CAMERA_MODEL_ESP_EYE)
    pinMode(13, INPUT_PULLUP);
    pinMode(14, INPUT_PULLUP);
  #endif
  
  // camera init
  esp_err_t err = esp_camera_init(&config);
  if (err != ESP_OK) {
    Serial.printf("Camera init failed with error 0x%x", err);
    return;
  }

  sensor_t * s = esp_camera_sensor_get();
  //initial sensors are flipped vertically and colors are a bit saturated
  if (s->id.PID == OV3660_PID) {
    s->set_vflip(s, 1);//flip it back
    s->set_brightness(s, 1);//up the blightness just a bit
    s->set_saturation(s, -2);//lower the saturation
  }
  //drop down frame size for higher initial frame rate
  //s->set_framesize(s, FRAMESIZE_QVGA);

  #if defined(CAMERA_MODEL_M5STACK_WIDE) || defined(CAMERA_MODEL_M5STACK_ESP32CAM)
    s->set_vflip(s, 1);
    s->set_hmirror(s, 1);
  #endif
  
}

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(".");
  }

  randomSeed(micros());

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

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP32-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (client.connect(clientId.c_str())) {
      Serial.println("connected");
      // Once connected, publish an announcement...
      client.publish("ei_out", "hello world");
      // ... and resubscribe
      client.subscribe("ei_in");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
}

void capture(){
  camera_fb_t *fb = esp_camera_fb_get();
  if(!fb){
      Serial.println("capture failed");
  }
  const uint8_t *data = (const uint8_t*)fb->buf;
  unsigned char base[500];
  String encoded = base64::encode(fb->buf, fb->len);

  boolean r = client.publish("srp",encoded.c_str());
  if(r){
    Serial.println("sent");
  }
  else{
    Serial.println("Not sent");
    //Serial.println(client.lastError());
  }

  //Serial.print("sent");
  delay(10000);
}

void setup() {
  initCam();
  Serial.begin(115200);
  setup_wifi();

  delay(1000);

   if (!SPIFFS.begin(true)) {
    Serial.println("An Error has occurred while mounting SPIFFS");
    return;
  }
  //=======================================
  //Root CA File Reading.
  File file2 = SPIFFS.open("/AmazonRootCA1.pem", "r");
  if (!file2) {
    Serial.println("Failed to open file for reading");
    return;
  }
  Serial.println("Root CA File Content:");
  while (file2.available()) {
    Read_rootca = file2.readString();
    Serial.println(Read_rootca);
  }
  //=============================================
  // Cert file reading
  File file4 = SPIFFS.open("/device-certificate.pem.crt", "r");
  if (!file4) {
    Serial.println("Failed to open file for reading");
    return;
  }
  Serial.println("Cert File Content:");
  while (file4.available()) {
    Read_cert = file4.readString();
    Serial.println(Read_cert);
  }
  //=================================================
  //Privatekey file reading
  File file6 = SPIFFS.open("/key-private.pem.key", "r");
  if (!file6) {
    Serial.println("Failed to open file for reading");
    return;
  }
  Serial.println("privateKey File Content:");
  while (file6.available()) {
    Read_privatekey = file6.readString();
    Serial.println(Read_privatekey);
  }
  
  
  //=====================================================

   char* pRead_rootca;
   pRead_rootca = (char *)malloc(sizeof(char) * (Read_rootca.length() + 1));
   strcpy(pRead_rootca, Read_rootca.c_str());

   char* pRead_cert;
   pRead_cert = (char *)malloc(sizeof(char) * (Read_cert.length() + 1));
   strcpy(pRead_cert, Read_cert.c_str());

   char* pRead_privatekey;
   pRead_privatekey = (char *)malloc(sizeof(char) * (Read_privatekey.length() + 1));
   strcpy(pRead_privatekey, Read_privatekey.c_str());



  Serial.println("================================================================================================");
  Serial.println("Certificates that passing to espClient Method");
  Serial.println();
  Serial.println("Root CA:");
  Serial.write(pRead_rootca);
  Serial.println("================================================================================================");
  Serial.println();
  Serial.println("Cert:");
  Serial.write(pRead_cert);
  Serial.println("================================================================================================");
  Serial.println();
  Serial.println("privateKey:");
  Serial.write(pRead_privatekey);
  Serial.println("================================================================================================");

  espClient.setCACert(pRead_rootca);
  espClient.setCertificate(pRead_cert);
  espClient.setPrivateKey(pRead_privatekey);

  client.setServer(mqtt_server, mqtt_port);
  client.setCallback(callback);

  //====================================================================================================================
  WiFi.macAddress(mac);
  snprintf(mac_Id, sizeof(mac_Id), "%02x:%02x:%02x:%02x:%02x:%02x",
           mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
  Serial.print(mac_Id);
  //=====================================================================================================================
  delay(2000);

}

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

  long now = millis();
  if (now - lastMsg > 2000) {
    lastMsg = now;
    capture();
  }

}

但是当我尝试发送 fb->buf 中的数据时（在将其类型转换为 const char* 之后），它被发送了。

我是物联网的新手，正在尝试学习如何将嵌入式系统与云集成。无论我做得对还是有任何其他替代方法来实现同样的目标，也能清楚地说明情况。

提前致谢！