GpioMap - a browser GPIO pin-mapper / diagnostics panel

Layer: L7 Application · Build flags: PC_ENABLE_GPIO_MAP

What this example teaches

This declares a compile-time table of GPIO pins (number, label, direction) and serves them at GET /gpio as JSON with live levels; POST /gpio (body pin=<n>&level=0|1) drives a pin marked as an output. A small inline page at / polls the JSON and renders the pin map with toggle buttons - a zero-dependency browser diagnostics tool. The JSON serializer and the control parser are host-tested; only the digital read/write run on the ESP32.

Declare the pins, then mount the endpoint. The table is caller-owned and must outlive the server; mark a pin PC_GPIO_OUT to make it drivable from the panel:

static pc_gpio_pin gpio_pins[] = {
    {2,  "Onboard LED", pc_gpio_dir::PC_GPIO_OUT,       0},
    {0,  "BOOT button", pc_gpio_dir::PC_GPIO_IN_PULLUP, 0},
    {4,  "Relay",       pc_gpio_dir::PC_GPIO_OUT,       0},
    {34, "ADC sense",   pc_gpio_dir::PC_GPIO_IN,        0},
};
 
pc_gpio_map_begin(server, "/gpio", gpio_pins, gpio_count); // applies pinMode, adds GET+POST /gpio

pc_gpio_map_begin() applies pinMode for each entry and registers both the JSON read route and the write route, so the only application code left is to serve the page that drives it.

Build and run

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

Flash, then open http://<ip>/ for the live pin map, or hit the API directly:

curl http://<ip>/gpio                                 # {"pins":[...]}
curl -X POST http://<ip>/gpio --data "pin=2&level=1"  # drive an output high

Annotated source

The complete sketch (GpioMap.ino), reproduced verbatim with added explanatory comments. The inline DIAG_PAGE HTML/JS string is elided here for length (see the source); it just fetches /gpio, renders a table, and POSTs toggles.

// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
#define PC_ENABLE_GPIO_MAP 1
 
#include "protocore.h"
#include "network_drivers/physical/physical.h"
#include "services/system/gpio_map/gpio_map.h"
 
static const char *SSID = "YOUR_SSID";
static const char *PASSWORD = "YOUR_PASSWORD";
 
PC server;
 
// The pins to expose. Caller-owned and must outlive the server. Mark a pin
// PC_GPIO_OUT to make it drivable from the panel.
static pc_gpio_pin gpio_pins[] = {
    {2, "Onboard LED", pc_gpio_dir::PC_GPIO_OUT, 0},
    {0, "BOOT button", pc_gpio_dir::PC_GPIO_IN_PULLUP, 0},
    {4, "Relay", pc_gpio_dir::PC_GPIO_OUT, 0},
    {34, "ADC sense", pc_gpio_dir::PC_GPIO_IN, 0},
};
static const uint8_t gpio_count = sizeof(gpio_pins) / sizeof(gpio_pins[0]);
 
// A tiny zero-dependency diag page: fetch /gpio, render rows, toggle outputs.
static const char DIAG_PAGE[] = R"HTML(... inline HTML/JS elided; see the source ...)HTML";
 
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));
 
    // GET /gpio (JSON) + POST /gpio (drive an output); pinMode is applied here.
    pc_gpio_map_begin(server, "/gpio", gpio_pins, gpio_count);
 
    server.on("/", HttpMethod::HTTP_GET, [](uint8_t id, HttpReq *) { server.send(id, 200, "text/html", DIAG_PAGE); });
    server.begin(80);
}
 
void loop()
{
    server.handle();
}