OtaRollback - OTA rollback protection / soft-brick safeguard

Layer: L7 Application · Build flags: PC_ENABLE_OTA_ROLLBACK

What this example teaches

A bad OTA image that boots but cannot do its job will soft-brick a remote device. The ESP32 bootloader can mark a freshly flashed image PENDING_VERIFY and roll back to the previous one unless the new firmware confirms itself. This wraps that mechanism: each loop it runs a self-test (here WiFi up + healthy heap) and ticks the rollback service - a passing self-test commits the image, a failing one (or no confirm within PC_OTA_CONFIRM_WINDOW_MS) rolls back. So a bad update self-heals instead of bricking. It is the safety net for the OTA upload in OTA.

Define a self-test, then tick until committed:

static bool self_test() { return wifi_ready() && ESP.getFreeHeap() > 20000; }
 
void loop() {
    static bool done = false;
    if (!done) {
        pc_ota_action a = pc_ota_rollback_tick(self_test());
        if (a == pc_ota_action::PC_OTA_COMMIT) { Serial.println("[ota] image committed"); done = true; }
    }
    server.handle();
}

pc_ota_rollback_tick(ok) is a no-op once the image is committed or on a normally-booted image, so it is safe to call every loop. pc_ota_img_state() reports the current image state for the /ota-state endpoint.

Requirement. Actual rollback needs the bootloader's app-rollback support (CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE) enabled in the build.

Build and run

pio ci --board=esp32dev --project-option="framework=arduino" \
  --project-option="build_flags=-DPC_ENABLE_OTA_ROLLBACK=1" \
  --lib="." examples/L7-Application/OtaRollback/OtaRollback.ino

curl http://<ip>/ota-state   # {"img_state":...} - the running image's verify state

Annotated source

The complete sketch (OtaRollback.ino), reproduced verbatim with added explanatory comments:

// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
#define PC_ENABLE_OTA_ROLLBACK 1
 
#include "protocore.h"
#include "network_drivers/physical/physical.h"
#include "services/system/ota_rollback/ota_rollback.h"
 
static const char *SSID = "YOUR_SSID";
static const char *PASSWORD = "YOUR_PASSWORD";
 
PC server;
 
// The health check that decides commit vs rollback. Put your real checks here.
static bool self_test()
{
    return wifi_ready() && ESP.getFreeHeap() > 20000;
}
 
void setup()
{
    Serial.begin(115200);
    init_wifi_physical(SSID, PASSWORD);
    while (!wifi_ready())
        delay(250);
    Serial.print("IP: ");
    uint32_t ip = pc_net_egress_ip(); // library egress IP (network byte order), no Arduino WiFi
    Serial.printf("IP: %u.%u.%u.%u\n", (unsigned)(ip & 0xFF), (unsigned)((ip >> 8) & 0xFF),
                  (unsigned)((ip >> 16) & 0xFF), (unsigned)((ip >> 24) & 0xFF));
 
    server.on("/ota-state", HttpMethod::HTTP_GET, [](uint8_t id, HttpReq *) {
        char b[48];
        snprintf(b, sizeof(b), "{\"img_state\":%u}", pc_ota_img_state());
        server.send(id, 200, "application/json", b);
    });
    server.begin(80);
}
 
void loop()
{
    // Confirm (or roll back) a freshly-updated image. A no-op once committed or on
    // a normally-booted image.
    static bool done = false;
    if (!done)
    {
        pc_ota_action a = pc_ota_rollback_tick(self_test());
        if (a == pc_ota_action::PC_OTA_COMMIT)
        {
            Serial.println("[ota] image committed");
            done = true;
        }
    }
    server.handle();
}