wenig
This commit is contained in:
chk
89
EmergencyStopButton/EmergencyStopButton.ino
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89
EmergencyStopButton/EmergencyStopButton.ino
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// EmergencyStopButton.ino
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// ESP32 – WiFi Light Sleep, wacht per GPIO-Interrupt auf Knopfdruck auf
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// und sendet sofort einen API-Call. Ziel: <250ms von Knopfdruck bis API.
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#include <WiFi.h>
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#include <HTTPClient.h>
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#include "esp_wifi.h"
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#include "esp_sleep.h"
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#include "driver/gpio.h"
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// ── Konfiguration ────────────────────────────────────────────────────────────
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#define BUTTON_PIN 9 // GPIO-Pin des Tasters (gegen GND)
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#define WIFI_SSID "DEIN_SSID"
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#define WIFI_PASSWORD "DEIN_PASSWORT"
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#define API_URL "https://deine-api.example.com/emergency-stop"
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#define API_TOKEN "DEIN_API_TOKEN"
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// ─────────────────────────────────────────────────────────────────────────────
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void connectWiFi() {
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WiFi.mode(WIFI_STA);
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WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
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Serial.print("WiFi verbinden");
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while (WiFi.status() != WL_CONNECTED) {
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delay(100);
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Serial.print(".");
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}
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Serial.printf("\nVerbunden. IP: %s\n", WiFi.localIP().toString().c_str());
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}
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void sendEmergencyStop() {
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if (WiFi.status() != WL_CONNECTED) {
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Serial.println("WiFi nicht verbunden – API-Call abgebrochen");
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return;
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}
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HTTPClient http;
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http.begin(API_URL);
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http.addHeader("Content-Type", "application/json");
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http.addHeader("Authorization", "Bearer " API_TOKEN);
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http.setTimeout(3000);
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String body = "{\"event\":\"emergency_stop\",\"device\":\"esp32-estop\"}";
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int httpCode = http.POST(body);
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if (httpCode > 0) {
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Serial.printf("API Response: %d\n", httpCode);
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} else {
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Serial.printf("HTTP Fehler: %s\n", http.errorToString(httpCode).c_str());
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}
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http.end();
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}
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void enterLightSleep() {
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// Wakeup bei LOW-Pegel (Taster gegen GND, Pull-Up aktiv)
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gpio_wakeup_enable((gpio_num_t)BUTTON_PIN, GPIO_INTR_LOW_LEVEL);
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esp_sleep_enable_gpio_wakeup();
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esp_light_sleep_start();
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// Ab hier läuft der Code weiter, sobald der Taster gedrückt wird
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}
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void setup() {
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Serial.begin(115200);
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pinMode(BUTTON_PIN, INPUT_PULLUP);
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connectWiFi();
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// DTIM=10: ESP32 wacht alle ~1000ms kurz für Beacon auf → ~0.5–1 mA
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esp_wifi_set_ps(WIFI_PS_MAX_MODEM);
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Serial.println("Bereit. Warte auf Knopfdruck...");
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}
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void loop() {
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enterLightSleep();
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// Wakeup → Taster prüfen (Low-aktiv wegen Pull-Up)
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if (digitalRead(BUTTON_PIN) == LOW) {
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unsigned long t0 = millis();
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sendEmergencyStop();
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Serial.printf("Latenz API-Call: %lu ms\n", millis() - t0);
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// Warten bis Taster losgelassen (Entprellung)
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while (digitalRead(BUTTON_PIN) == LOW) {
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delay(10);
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}
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delay(50);
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}
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}
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BIN
EmergencyStopButton/eStopESP32.pdf
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BIN
EmergencyStopButton/eStopESP32.pdf
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Binary file not shown.
237
EmergencyStopButton/eStopESP32.tex
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237
EmergencyStopButton/eStopESP32.tex
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\documentclass[a4paper,11pt]{article}
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\usepackage[utf8]{inputenc}
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\usepackage[T1]{fontenc}
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\usepackage[ngerman]{babel}
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\usepackage{geometry}
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\usepackage{amsmath}
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\usepackage{booktabs}
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\usepackage{listings}
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\usepackage{xcolor}
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\usepackage[unicode=true]{hyperref}
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\usepackage{enumitem}
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\lstset{
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basicstyle=\ttfamily\small,
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keywordstyle=\color{blue},
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commentstyle=\color{gray},
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stringstyle=\color{orange},
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backgroundcolor=\color{gray!10},
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frame=single,
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breaklines=true,
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columns=fullflexible
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}
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\title{\textbf{Emergency Stop Button -- ESP32}\\
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\large Technische Dokumentation}
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\author{}
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\date{Juni 2026}
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\begin{document}
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\maketitle
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\tableofcontents
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\newpage
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% -----------------------------------------------
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\section{Ziel und Anforderungen}
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Ein physischer Notaus-Taster soll beim Drücken so schnell wie möglich einen
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API-Call absetzen. Der ESP32 befindet sich im Ruhezustand und wird durch den
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Tastendruck geweckt.
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\begin{itemize}
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\item Latenz Knopfdruck $\rightarrow$ API-Call: \textbf{< 250\,ms}
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\item Stromversorgung: LiPo 1000\,mAh (kabellos, batteriebetrieben)
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\item Möglichst lange Akkulaufzeit (Taster wird selten gedrückt, $\leq$1\,×/h)
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\item Einfache, wartungsarme Architektur
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\end{itemize}
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% -----------------------------------------------
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\section{Architekturentscheidung}
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\subsection{Bewertete Optionen}
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\begin{center}
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\begin{tabular}{lllll}
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\toprule
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Option & Latenz & Ø Strom & Gateway nötig & Komplexität \\
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\midrule
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Deep Sleep + WiFi (RTC-Memory) & 600--1300\,ms & $\approx$0{,}02\,mA & nein & niedrig \\
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\textbf{WiFi Light Sleep (DTIM=10)} & \textbf{150--250\,ms} & \textbf{0{,}5--1\,mA} & \textbf{nein} & \textbf{niedrig} \\
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BLE Light Sleep + Gateway & 100--300\,ms & 0{,}5--2\,mA & ja & hoch \\
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\bottomrule
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\end{tabular}
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\end{center}
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\subsection{Entscheidung: WiFi Light Sleep}
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WiFi Light Sleep erfüllt alle Anforderungen ohne zusätzliche Infrastruktur:
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\begin{itemize}
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\item Der ESP32 hält die WiFi-Verbindung aufrecht und schläft nur die CPU
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\item Ein GPIO-Interrupt weckt den ESP32 sofort beim Tastendruck
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\item Der API-Call geht direkt vom ESP32 -- kein Container, kein Gateway
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\end{itemize}
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\textbf{Warum nicht BLE?} Bluetooth LE wäre minimal sparsamer
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($\approx$0{,}5\,mA vs. $\approx$1\,mA), erfordert aber ein dauerhaft laufendes
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Gateway-Gerät (Raspberry Pi, PC), das seinerseits Strom verbraucht und eine
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Fehlerquelle darstellt.
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\textbf{Warum nicht Deep Sleep?} Deep Sleep braucht beim Aufwachen
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600--1300\,ms (WiFi-Reconnect), was die Latenzanforderung von 250\,ms
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verfehlt.
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% -----------------------------------------------
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\section{WiFi Light Sleep -- Funktionsprinzip}
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Im WiFi Light Sleep (Modem Sleep) schläft die CPU, während der WiFi-Stack
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aktiv bleibt. Der Router sendet alle 100\,ms einen Beacon; mit DTIM=10 wacht
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der ESP32 automatisch alle $\approx$1000\,ms für 1--2\,ms auf, um gepufferte
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Pakete abzuholen. Die Verbindungsassoziation bleibt dabei erhalten.
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\subsection{DTIM-Einstellung und Stromverbrauch}
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\begin{center}
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\begin{tabular}{lll}
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\toprule
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DTIM & Wakeup-Intervall & Ø Strom \\
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\midrule
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1 & 100\,ms & 5--10\,mA \\
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3 & 300\,ms & 2--4\,mA \\
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10 & 1000\,ms & 0{,}5--1\,mA \\
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\bottomrule
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\end{tabular}
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\end{center}
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Empfohlen: \texttt{DTIM=10} -- sparsamste Option, Verbindung bleibt stabil.
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\subsection{Akkulaufzeit (1000 mAh LiPo)}
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Bei $\approx$1\,mA Durchschnittsstrom (DTIM=10, selten gedrückt):
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\[
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t = \frac{1000~\mathrm{mAh}}{1~\mathrm{mA}} \approx 40~\mathrm{Tage}
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\]
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% -----------------------------------------------
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\section{Latenzbudget}
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\begin{center}
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\begin{tabular}{ll}
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\toprule
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Schritt & Zeit \\
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\midrule
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ESP32 Wakeup aus Light Sleep & 1--5\,ms \\
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WiFi-Verbindung prüfen (bereits aktiv) & 0\,ms \\
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HTTP-Request aufbauen & 20--50\,ms \\
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TLS-Handshake (HTTPS) & 50--150\,ms \\
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Server-Antwort & 20--50\,ms \\
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\midrule
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\textbf{Gesamt} & \textbf{$\approx$100--250\,ms} \\
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\bottomrule
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\end{tabular}
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\end{center}
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% -----------------------------------------------
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\section{Hardware}
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\subsection{Empfohlene Boards}
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\begin{center}
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\begin{tabular}{llll}
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\toprule
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Board & Lader & Preis & Bemerkung \\
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\midrule
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\textbf{FireBeetle ESP32-E} (DFRobot) & integriert & 8--12\,€ & Low-Power optimiert \\
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LOLIN D32 (Wemos) & TP4054 & 5--8\,€ & günstig, bewährt \\
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Adafruit HUZZAH32 Feather & MCP73831 & $\approx$20\,€ & gute Dokumentation \\
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\bottomrule
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\end{tabular}
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\end{center}
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\subsection{Schaltung}
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\begin{lstlisting}
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ESP32 Taster
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GPIO 9 ---- [Taster] ---- GND
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(interner Pull-Up aktiv: HIGH = offen, LOW = gedrueckt)
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LiPo 1000mAh ---- BAT+ / BAT- des Boards
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\end{lstlisting}
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Kein weiteres Bauteil nötig -- der interne Pull-Up des ESP32 reicht.
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% -----------------------------------------------
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\section{Software}
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\subsection{Abhängigkeiten (Arduino IDE)}
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\begin{itemize}
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\item Board-Package: \texttt{esp32} by Espressif (Boards Manager)
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\item Bibliotheken: \texttt{WiFi.h}, \texttt{HTTPClient.h} (im esp32-Package enthalten)
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\end{itemize}
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\subsection{Konfiguration in \texttt{EmergencyStopButton.ino}}
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\begin{lstlisting}[language=C]
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#define BUTTON_PIN 9
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#define WIFI_SSID "DEIN_SSID"
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#define WIFI_PASSWORD "DEIN_PASSWORT"
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#define API_URL "https://deine-api.example.com/emergency-stop"
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#define API_TOKEN "DEIN_API_TOKEN"
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\end{lstlisting}
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\subsection{Ablauf}
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\begin{enumerate}
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\item \texttt{setup()}: WiFi verbinden, \texttt{WIFI\_PS\_MAX\_MODEM} aktivieren
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\item \texttt{loop()}: \texttt{esp\_light\_sleep\_start()} -- CPU schläft, WiFi aktiv
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\item Tastendruck löst GPIO-Interrupt aus -- ESP32 wacht auf
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\item \texttt{sendEmergencyStop()} sendet HTTP-POST an API
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\item Warten bis Taster losgelassen, zurück zu Schritt 2
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\end{enumerate}
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\subsection{Kritische API-Funktion}
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\begin{lstlisting}[language=C]
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void sendEmergencyStop() {
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HTTPClient http;
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http.begin(API_URL);
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http.addHeader("Content-Type", "application/json");
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http.addHeader("Authorization", "Bearer " API_TOKEN);
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http.setTimeout(3000);
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String body = "{\"event\":\"emergency_stop\",\"device\":\"esp32-estop\"}";
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int httpCode = http.POST(body);
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http.end();
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}
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\end{lstlisting}
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% -----------------------------------------------
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\section{Deployment-Hinweise}
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\begin{itemize}
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\item \textbf{HTTPS}: TLS-Handshake kostet 50--150\,ms. Falls die Latenz
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kritisch ist und das Netz vertrauenswürdig, kann HTTP verwendet werden
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(dann $\approx$50--100\,ms Gesamt).
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\item \textbf{DTIM am Router}: Manche Router ignorieren den DTIM-Wunsch des
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Clients. Im Zweifelsfall DTIM=3 am Router einstellen.
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\item \textbf{API-Token}: Nicht im Quellcode einchecken -- z.\,B. in eine
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separate \texttt{secrets.h} auslagern, die im \texttt{.gitignore} steht.
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\item \textbf{Watchdog}: Bei produktivem Einsatz einen Hardware-Watchdog
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aktivieren, damit der ESP32 sich bei WiFi-Verlust selbst neu startet.
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\end{itemize}
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% -----------------------------------------------
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\section{Dateien}
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\begin{center}
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\begin{tabular}{ll}
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\toprule
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Datei & Beschreibung \\
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\midrule
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\texttt{EmergencyStopButton.ino} & Arduino-Sketch (Hauptprogramm) \\
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\texttt{eStopESP32.tex} & Diese Dokumentation \\
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\bottomrule
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\end{tabular}
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\end{center}
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\end{document}
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Reference in New Issue
Block a user