Layer: L7 Application · Build flags: PC_ENABLE_PARTITION_MONITOR

What this example teaches

The ESP32's flash is carved into partitions (factory app, OTA slots, NVS, LittleFS, ...). pc_partition_monitor_begin() serves that table as JSON at /partitions: each entry's label, kind, type/subtype, flash offset, and size, plus which app slot is currently running. It is a one-call diagnostics endpoint that pairs well with OTA dashboards, and it needs no special hardware.

One call mounts the endpoint:

pc_partition_monitor_begin(server, "/partitions");

The handler reads the partition table from the ESP-IDF API and serializes it directly into the response (no heap).

Build and run

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

curl http://<ip>/partitions # JSON: labels, offsets, sizes, running slot

Annotated source

The complete sketch (PartitionMonitor.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_PARTITION_MONITOR 1
 
#include "protocore.h"
#include "network_drivers/physical/physical.h"
#include "services/storage/partition_monitor/partition_monitor.h"
 
static const char *SSID = "YOUR_SSID";
static const char *PASSWORD = "YOUR_PASSWORD";
 
PC server;
 
void setup()
{
    Serial.begin(115200);
    init_wifi_physical(SSID, PASSWORD);
    Serial.print("Connecting to WiFi");
    while (!wifi_ready())
    {
        delay(250);
        Serial.print('.');
    }
    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));
 
    // Serve the flash partition table as JSON at /partitions.
    pc_partition_monitor_begin(server, "/partitions");
    server.begin(80);
}
 
void loop()
{
    server.handle();
}