One of the things the ESP8266 is ideal for is the whole IoT thing. For that, you do need to be able to connect it to a WiFi network and configure it. If your device doesn't have an user interface, this can be quite hard. The device has an AP mode though. Couldn't you just use that and run a webserver to configure it? Well yes, but you'd need a webserver for that...
Introducing esphttpd, a http server for the ESP8266. Open-source, reasonably robust, modular, easy to use (I hope).
- Open-source, beerware
- Code is in git: http://git.spritesserver.nl/esphttpd.git/
- Go ahead, kill my ESP: http://18.104.22.168:8081/index.tpl
- Have an useful patches or pull-requests? Mail me: jeroen at-symbol spritesmods period com
The git source codebase above is for an example project using the http server. The second url leads to one of my ESPs. Don't be surprised if it doesn't react anymore or has rebooted a few times: you know the specs of the li'l beast and I just released the Internet at large at it... Ah, and I disabled the WiFi page; wouldn't want you to switch it over to the neighbours WiFi-network.
ABOUT THE WEBSERVER
The Good (aka: what's awesome)
- Supports multiple connections, for eg simultaneous html/css/js/images downloading
- Static files stored in flash, in an (optionally compressed) RO filesystem
- Pluggable using external cgi routines
- Simple template engine for mixed c and html things
The Bad (aka: what can be improved)
- Not built for speediness, although it's reasonable fast.
- Built according to what I remember of the HTTP protocol, not according to the
RFCs. Should work with most modern browsers, though.
- No support for authentication or https.
The Ugly (aka: bugs, misbehaviour)
- Possible buffer overflows (usually not remotely exploitable) due to no os_snprintf
This can be theoretically remedied by either Espressif including an os_snprintf in.
their libs or by using some alternate printf lib, like elm-chans xprintf
ABOUT THE EXAMPLE
When you flash the example into an ESP8266(EX) module, you get a small webserver with a few example
pages. If you've already connected your module to your WLAN before, it'll keep those settings. When
you haven't or the settings are wrong, keep GPIO0 for >5 seconds. The module will reboot into
its STA+AP mode. Connect a computer to the newly formed access point and browse to.
http://192.168.4.1/wifi in order to connect the module to your WiFi network. The example also
allows you to control a LED that's connected to GPIO2.
For this, you need an environment that can compile ESP8266 firmware. Environments for this still
are in flux at the moment, but I'm using a crosstool-ng gcc setup combined with the libs & includes
from the ESP SDK and ESP VM. You probably also need an UNIX-slike system; I'm working on
Debian Linux myself..
To manage the paths to all this, you can source a small shell fragment into your current session. For
example, I source a file with these contents:
Actual setup of the SDK and toolchain is out of the scope of this document, so I hope this helps you
enough to set up your own if you haven't already.
If you have that, you can clone out the source code:
git clone http://git.spritesserver.nl/esphttpd.git/
This project makes use of heatshrink, which is a git submodule. To fetch the code:
git submodule init
git submodule update
Now, build the code:
Flash the code happens in 2 steps. First the code itself gets flashed. Reset the module into bootloader
mode and enter 'make flash'. You may want to reset and re-enter the bootloader halfway (at 'sleep 3') for
the 2nd part of this flash to work.
The 2nd step is to pack the static files the webserver will serve and flash that. Reset the module into
bootloader mode again and enter 'make htmlflash'.
You should have a working webserver now.
WRITING CODE FOR THE WEBSERVER
...errm... to be done. For now, look at the examples. Hey, you probably managed to find out how
the SDK works, this shouldn't be too hard