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<!-- { "title": "Configuration-Webserver for ESP8266 Projects" } -->
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<p>
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In my previous ESP8266 based weekend projects I always hardcoded configuration data. For the ESP8266 these are at least the WiFi credentials SSID and WPA key. Moving it into a different WiFi network requires re-flashing it. There must be a better way I thought and found that's a single line of code to run the ESP8266 as an accesspoint, which opens its own WiFi network.
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</p>
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<p>
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So, I first hardcoded a web page with a form to enter configuration data, a data structure to hold it and some code to store it into the EEPROM or load it there.
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It appears that this was an error-prone process with a lot of redudancy in the code.
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</p>
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<p>
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For that reason I wrote an approach with a small template-based generator script:
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</p>
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<p>
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<pre>
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<code "language"="python">
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#!/usr/bin/python
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from Cheetah.Template import Template
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configItems = [
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{ "label" : "_" , "key" : "magic" , "type" : "I" , "default" : 0 },
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{ "label" : "Wifi SSID" , "key" : "wifiSsid" , "type" : "C" , "length" : 32, "default" : "test" },
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{ "label" : "Wifi Key" , "key" : "wifiKey" , "type" : "C" , "length" : 64, "default" : "geheim" },
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{ "label" : "MQTT Broker" , "key" : "mqttBroker" , "type" : "C" , "length" : 64, "default" : "broker.hottis.de" },
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{ "label" : "MQTT Username" , "key" : "mqttUser" , "type" : "C" , "length" : 32, "default" : "esp1" },
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{ "label" : "MQTT Password" , "key" : "mqttPass" , "type" : "C" , "length" : 32, "default" : "geheim" },
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{ "label" : "MQTT ClientId" , "key" : "mqttClientId" , "type" : "C" , "length" : 32, "default" : "changeThis" },
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{ "label" : "MQTT Topic" , "key" : "mqttTopic" , "type" : "C" , "length" : 64, "default" : "IoT/espThermometer2/location/measurement" },
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{ "label" : "MQTT Port" , "key" : "mqttPort" , "type" : "I" , "default" :8883},
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{ "label" : "Measure Period" , "key" : "measurePeriod" , "type" : "I" , "default" :300}
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]
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h_file = Template(file= configuration_h.tmpl , searchList=[{ configItems :configItems}])
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open('configuration.h','w').write(str(h_file))
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c_file = Template(file= configuration_c.tmpl , searchList=[{ configItems :configItems}])
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open('configuration.cpp','w').write(str(c_file))
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</code>
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</pre>
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</p>
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<p>
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The two templates are:
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</p>
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<p>
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<pre>
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<code "language"="C">
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typedef struct {
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#for $configItem in $configItems
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#if $configItem.type == 'C'
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char ${configItem.key}[$configItem.length];
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#else if $configItem.type == 'I'
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uint32_t $configItem.key;
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#end if
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#end for
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} tConfigBlock;
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extern const uint32_t MAGIC;
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extern tConfigBlock configBlock;
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void configServeIndex();
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void configServeGetConfiguration();
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void showConfiguration();
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</code>
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</pre>
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</p>
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<p>
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And:
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</p>
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<p>
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<pre>
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<code language="C">
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#raw
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#include <Arduino.h>
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#include <ESP8266WiFi.h>
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#include <ESP8266WebServer.h>
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#include <EEPROM.h>
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#include "defines.h"
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#include "configuration.h"
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#end raw
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tConfigBlock configBlock;
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const uint32_t MAGIC = 0xC0DE0001;
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extern ESP8266WebServer webServer;
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bool configSaved = false;
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void configServeIndex() {
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bool configValid = (configBlock.magic == MAGIC);
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if (! configValid) {
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#for $configItem in $configItems
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#if $configItem.label != "_"
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#if $configItem.type == "C"
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strcpy(configBlock.$configItem.key, "$configItem.default");
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#else if $configItem.type == "I"
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configBlock.$configItem.key = $configItem.default;
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#end if
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#end if
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#end for
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}
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String buffer =
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"<!doctype html"
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"<html lang=\"en\">"
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" <head>"
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" <title>ESP8266 Thermometer Configuration Page</title>"
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" </head>"
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" <body>"
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" <h1>ESP8266 Configuration Page</h1>";
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if (configSaved) {
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configSaved = false;
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buffer += "<h2>Configuration saved</h2>";
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}
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buffer +=
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" <form action=\"/config\" method=\"GET\">"
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" <table>"
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#for $configItem in $configItems
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#if $configItem.label != "_"
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" <tr>"
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" <td>"
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" <label for\"$configItem.key\">$configItem.label</label>"
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" </td><td>"
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" <input type=\"text\" name=\"$configItem.key\" id=\"$configItem.key\" ";
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#if $configItem.type == "C"
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buffer += " size=\"$configItem.length\" ";
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buffer += " value=\"";
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buffer += configBlock.$configItem.key;
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buffer += "\"";
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#else if $configItem.type == "I"
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buffer += " value=\"";
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buffer += configBlock.$configItem.key;
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buffer += "\"";
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#end if
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buffer +=
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" />"
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" </td>"
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" </tr>"
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#end if
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#end for
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" <tr>"
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" <td colspan=\"2\">"
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" <button type=\"submit\">Save</button>"
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" </td>"
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" </tr>"
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" </table>"
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" </form>"
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" </body>"
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"</html>";
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webServer.send(200, "text/html", buffer);
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#ifdef DEBUG
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Serial.println("indexHtml request served");
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#endif
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}
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void configServeGetConfiguration() {
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String arg;
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#for $configItem in $configItems
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#if $configItem.label != "_"
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arg = webServer.arg("$configItem.key");
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#if $configItem.type == "C"
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strcpy(configBlock.$configItem.key, arg.c_str());
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#else if $configItem.type == "I"
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configBlock.$configItem.key = atoi(arg.c_str());
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#end if
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#end if
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#end for
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configBlock.magic = MAGIC;
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showConfiguration();
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EEPROM.begin(512);
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EEPROM.put(EEPROM_ADDR, configBlock);
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EEPROM.commit();
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Serial.println("EEPROM saved");
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configSaved = true;
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webServer.sendHeader("Location", String("/"), true);
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webServer.send(302, "text/plain", "");
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//webServer.send(200, "text/html", "configuration saved");
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}
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void showConfiguration() {
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Serial.println("Configuration is");
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#for $configItem in $configItems
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Serial.print("$configItem.key = ");
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Serial.println(configBlock.$configItem.key);
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#end for
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Serial.println("---");
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}
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</code>
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</pre>
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</p>
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<p>
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Besides these generated files I also needed a framework to distinguish between "configuration mode" and "production mode" and in configuration mode to start the WiFi accesspoint.
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</p>
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<p>
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Since I'm programming the ESP8266 in an Eclipse-based Arduino-environment, this is all done in the <code>setup()</code> and <code>loop()</code> function:
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</p>
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<p>
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<pre>
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<code language="C">
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// Do not remove the include below
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#include "EspThermometer2.h"
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#include "defines.h"
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// #define ESP8266
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#include <EEPROM.h>
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#include "configuration.h"
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#include "productionMode.h"
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#include "configurationMode.h"
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ADC_MODE(ADC_VCC);
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bool configMode = false;
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uint32_t startTime = 0;
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void setup() {
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startTime = millis();
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#ifdef DEBUG
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Serial.begin(115200);
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Serial.println("Starting ...");
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#endif
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pinMode(CONFIG_SWITCH, INPUT_PULLUP);
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pinMode(LED_PIN, OUTPUT);
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EEPROM.begin(512);
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EEPROM.get(EEPROM_ADDR, configBlock);
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Serial.print("Magic: ");
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Serial.println(configBlock.magic);
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configMode = ((LOW == digitalRead(CONFIG_SWITCH)) || (configBlock.magic != MAGIC));
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if (configMode) {
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#ifdef DEBUG
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Serial.println("Configuration mode");
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#endif
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digitalWrite(LED_PIN, LOW);
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setupConfigurationNetwork();
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setupConfigurationServer();
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} else {
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#ifdef DEBUG
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Serial.println("Production mode");
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Serial.println();
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Serial.println();
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showConfiguration();
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#endif
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digitalWrite(LED_PIN, HIGH);
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setupProduction();
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setupConfigurationServer();
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}
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#ifdef DEBUG
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Serial.println("Started.");
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#endif
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}
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void loop() {
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if (configMode) {
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loopConfiguration();
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} else {
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loopProduction();
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}
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}
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</code>
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</pre>
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</p>
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<p>
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This code can be also found embedded into two of my projects. Find them at <a href="https://gitlab.com/wolutator/EspThermometer2" target="_blank">https://gitlab.com/wolutator/EspThermometer2</a> and <a href="https://gitlab.com/wolutator/TouchSwitch" target="_blank">https://gitlab.com/wolutator/TouchSwitch</a>.
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</p>
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