Diagnostics - a compile-time configuration endpoint

Layer: L7 Application · Build flags: PC_ENABLE_DIAG

What this example teaches

server.diag(slot_id) serves PC_DIAG_JSON, a compile-time snapshot of which features are enabled and how the buffers are sized. It is handy while developing - one route tells you exactly what the firmware was built with - but because it exposes the build configuration, keep it off (or behind auth) in production.

One call renders the build snapshot:

server.on("/diag", HttpMethod::HTTP_GET, [](uint8_t id, HttpReq *) { server.diag(id); });

The JSON is assembled at compile time from the active PC_* macros, so the endpoint adds essentially nothing at runtime and cannot drift from the real configuration.

Build and run

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

curl http://<ip>/diag   # JSON: enabled features + buffer sizes

Annotated source

The complete sketch (Diagnostics.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_DIAG 1
 
#include "protocore.h"
#include "network_drivers/physical/physical.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 compile-time configuration snapshot. Keep this off in production.
    server.on("/diag", HttpMethod::HTTP_GET, [](uint8_t id, HttpReq *) { server.diag(id); });
    server.begin(80);
}
 
void loop()
{
    server.handle();
}