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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.

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. It appears that this was an error-prone process with a lot of redudancy in the code.

For that reason I wrote an approach with a small template-based generator script:

#!/usr/bin/python

from Cheetah.Template import Template

configItems = [
    { "label" : "_" ,  "key" : "magic" ,  "type" : "I" ,  "default" : 0 },
    { "label" : "Wifi SSID" ,  "key" : "wifiSsid" ,  "type" : "C" ,  "length" : 32,  "default" : "test" },
    { "label" : "Wifi Key" ,  "key" : "wifiKey" ,  "type" : "C" ,  "length" : 64,  "default" : "geheim" },
    { "label" : "MQTT Broker" ,  "key" : "mqttBroker" ,  "type" : "C" ,  "length" : 64,  "default" : "broker.hottis.de" },
    { "label" : "MQTT Username" ,  "key" : "mqttUser" ,  "type" : "C" ,  "length" : 32,  "default" : "esp1" },
    { "label" : "MQTT Password" ,  "key" : "mqttPass" ,  "type" : "C" ,  "length" : 32,  "default" : "geheim" },
    { "label" : "MQTT ClientId" ,  "key" : "mqttClientId" ,  "type" : "C" ,  "length" : 32,  "default" : "changeThis" },
    { "label" : "MQTT Topic" ,  "key" : "mqttTopic" ,  "type" : "C" ,  "length" : 64,  "default" : "IoT/espThermometer2/location/measurement" },
    { "label" : "MQTT Port" ,  "key" : "mqttPort" ,  "type" : "I" ,  "default" :8883},
    { "label" : "Measure Period" ,  "key" : "measurePeriod" ,  "type" : "I" ,  "default" :300}
]

h_file = Template(file= configuration_h.tmpl , searchList=[{ configItems :configItems}])
open('configuration.h','w').write(str(h_file))
c_file = Template(file= configuration_c.tmpl , searchList=[{ configItems :configItems}])
open('configuration.cpp','w').write(str(c_file))

Using the both templates for a C- and a H-file all the code for the configuration web page, the EEPROM handling code and the code to access the configuration variables is generated.

The functions provided using these templates in turn a call from a rather simple configuration mode. In pure configuration mode (when the device is unconfigured or the configuration mode is requested using a pulled-down pin) a new WLAN will be opened using the accesspoint functionality of the ESP8266. In production mode, the configuration accesspoint is not started, however, the configuration mode webserver is started nevertheless.

This code can be also found embedded in several of my projects. Find them at https://gitlab.com/wolutator/EspThermometer2, https://gitlab.com/wolutator/TouchSwitch, https://gitlab.com/wolutator/MySwitch, https://gitlab.com/wolutator/RainSensor and https://gitlab.com/wolutator/TwoLedSignal.