ESP32 Multi-Application Bootloader: Run Multiple Apps on a Single Device

# Name,      Type, SubType,   Offset,  Size, Flags
nvs,         data, nvs,       0x9000,   24K,
otadata,     data, ota,       ,         8K,
phy_init,    data, phy,       ,         4K,
factory,     app,  factory,   ,         2M,
ota_0,       app,  ota_0,     ,         2M,
ota_1,       app,  ota_1,     ,         2M,
ota_2,       app,  ota_2,     ,         2M,

#include 
#include 
#include 

// Define the menu options
typedef struct {
  const char* name;
  const char* description;
  const esp_partition_subtype_t subtype;
} app_info_t;

// Our three apps plus the bootloader itself
app_info_t apps[] = {
  {"Bootloader", "Main Menu (current)", ESP_PARTITION_SUBTYPE_APP_FACTORY},
  {"LED Patterns", "Different LED blinking patterns", ESP_PARTITION_SUBTYPE_APP_OTA_0},
  {"Temp Sensor", "Temperature sensor simulator", ESP_PARTITION_SUBTYPE_APP_OTA_1},
  {"Echo Test", "Serial echo and character counter", ESP_PARTITION_SUBTYPE_APP_OTA_2}
};

// ASCII art header
void printHeader() {
  Serial.println();
  Serial.println("  ______  _____ _____ ____ ___    _____ ____  ");
  Serial.println(" | ____/ |  ___/ ____|  _ \\_ _|  | ____|___ \\ ");
  Serial.println(" |  _|   | |_  | |  _ | |_) | |   |  _|   __) |");
  Serial.println(" | |___  |  _| | |_| ||  __/| |   | |___ / __/ ");
  Serial.println(" |_____| |_|    \\____|_|   |___|  |_____|_____|");
  Serial.println();
  Serial.println("       MULTI-APPLICATION BOOTLOADER DEMO       ");
  Serial.println("============================================");
}

// Display the menu of available applications
void displayMenu() {
  printHeader();
  Serial.println("Available Applications:");
  Serial.println();
  
  for(int i = 1; i < sizeof(apps)/sizeof(app_info_t); i++) {
    Serial.print("  ");
    Serial.print(i);
    Serial.print(". ");
    Serial.print(apps[i].name);
    Serial.print(" - ");
    Serial.println(apps[i].description);
  }
  
  Serial.println();
  Serial.println("Enter application number (1-3):");
}

// Switch to the selected application
void switchToApp(int appIndex) {
  if(appIndex < 1 || appIndex >= sizeof(apps)/sizeof(app_info_t)) {
    Serial.println("Invalid selection!");
    return;
  }
  
  // Find the partition for the selected app
  const esp_partition_t* next_partition = esp_partition_find_first(
    ESP_PARTITION_TYPE_APP, 
    apps[appIndex].subtype, 
    NULL);
    
  if(next_partition && esp_ota_set_boot_partition(next_partition) == ESP_OK) {
    Serial.print("Switching to ");
    Serial.println(apps[appIndex].name);
    Serial.println("Restarting in 3 seconds...");
    delay(3000);
    ESP.restart();  // Restart to boot from the new partition
  } else {
    Serial.println("ERROR: Failed to set boot partition!");
    Serial.println("Application may not be installed or partition table is incorrect.");
  }
}

void setup() {
  // Initialize serial and wait for it to connect
  Serial.begin(115200);
  delay(1000);
  
  // Show device information
  const esp_partition_t* running = esp_ota_get_running_partition();
  
  printHeader();
  Serial.println("System Information:");
  Serial.print("  ESP32 Chip Model: ");
  Serial.println(ESP.getChipModel());
  Serial.print("  Flash Size: ");
  Serial.print(ESP.getFlashChipSize() / (1024 * 1024));
  Serial.println(" MB");
  Serial.print("  Free Heap: ");
  Serial.print(ESP.getFreeHeap() / 1024);
  Serial.println(" KB");
  Serial.print("  Current Partition: ");
  Serial.println(running->label);
  Serial.println();
  
  Serial.println("Press any key to continue...");
}

void loop() {
  // Wait for user input
  if(Serial.available() > 0) {
    // Clear any pending input
    while(Serial.available()) {
      Serial.read();
    }
    
    // Show the menu
    displayMenu();
    
    // Wait for application selection
    while(!Serial.available()) {
      delay(100); // Wait for input
    }
    
    int choice = Serial.parseInt();
    Serial.print("Selected: ");
    Serial.println(choice);
    
    if(choice >= 1 && choice <= 3) {
      switchToApp(choice);
    } else {
      Serial.println("Invalid selection! Please try again.");
      delay(2000);
    }
  }
  
  delay(100);
}

#include 
#include 
#include 

// Function to set the next boot to the factory partition (bootloader)
void reset_to_factory_app() {
  const esp_partition_t *factory_partition = esp_partition_find_first(
    ESP_PARTITION_TYPE_APP, 
    ESP_PARTITION_SUBTYPE_APP_FACTORY, 
    NULL);
    
  if (factory_partition != NULL) {
    if (esp_ota_set_boot_partition(factory_partition) == ESP_OK) {
      Serial.println("Set boot partition to bootloader");
    } else {
      Serial.println("Failed to set boot partition!");
    }
  } else {
    Serial.println("Factory partition not found!");
  }
}

void setup() {
  Serial.begin(115200);
  
  // IMPORTANT: Set the next boot to return to the bootloader
  reset_to_factory_app();
  
  // Your application initialization code goes here
  Serial.println("\n\n=== YOUR APPLICATION NAME ===");
  // ...
}

void loop() {
  // Your application main code goes here
  // ...
  
  // Optional: Add a way to manually return to bootloader
  if (Serial.available() > 0) {
    char cmd = Serial.read();
    if (cmd == 'b') {
      Serial.println("Returning to bootloader...");
      delay(1000);
      ESP.restart();
    }
  }
}