WiFi for everything

A few years ago making a hobby circuit WiFi capable costed at least 30$-40$. In the past year Espressif Systems introduced a very cheap and smart solution for WiFi connectivity.

In my old-new blog I am going to present my applications and experiments regarding it's new WiFi product.

ESP8266 is a highly integrated chip with complete and self-contained WiFi networking solution, either to host an application or to offload all WiFi networking functions from another application processor. It contains a 32-bit RISC processor, on-chip memory and external memory interfaces.

On the market are many types of module variants built-up from this chip, with or without antenna. I am using this variant, which costs 3$:

The firmware of the chip is still being developed by the producer, in addition an open source SDK is available as well. That means, the users are able to write programs directly to the chip without using a host microcontroller. Besides, the users can use several hardware peripherals (Flash memory, UART, SPI, GPIO, ...) as well.

Every SDK package contains an official AT firmware, which is flashed into the chip by default. It is useful, when the user has a host controller in the application, and does not want to use the ESP chip as a master CPU. In this case the WiFi module is just a slave. In order to communicate with the chip, a simple serial data transfer is being used (UART) with AT commands. These are ASCII commands, so it is quite simple to test the module using a serial terminal program on PC.

I chose this AT firmware, because it is simpler, it is under the development of the manufacturer, and I did not want to use the SDK. I wanted the module only manage the WiFi stuff, and not the whole application.

To be honest, AT commands are easy to read for a human being, but a little bit difficult to interpret in a microcontroller. Actually, it is not so hard, but I did not want to implement a complex two-way serial communication in my all programs over and over again. In my opinion UART is just a low-level communication, and in the host microcontroller's code I want to use only mid- and high-level functions (WiFi, UDP, TCP, HTTP).

Therefore, my first goal was to create a software library for the microcontroller, which manages the communication with the AT firmware. The development was a little bit difficult and long, because the command sheet of the firmware is not quite complete and clear. The chip gave in some circumstances weird responses, so I needed to check all the commands and replies using a PC serial terminal program. That means a lot of times :-)

My library supports now settings, WiFi-related, and TCP/UDP data transfer functions, and was compiled in mikroC. Some of the AT commands are missing yet, but these are not so crucial. You can download it from here.

I made a little test hardware based on a PIC18F14K50 microcontroller to try the UDP communication out. It worked very well, you can see it in the video below.

The next step is a long term TCP test. I will probably use a temperature sensor in the circuit, and will try to get the actual temperature value using a Windows or Windows Phone 8.1 app. Nothing complicated, just dealing with TCP sockets...