ESP Basics

The ESP8266 chip incorporates complete WiFi capability in a tiny package that's about 1/4" square. The chip is used on several versions of ESP modules, such as the popular and inexpensive ESP-01 version, shown below:

The module is programmable using the Arduino interface and since introduced in 2013, a great many Arduino interface add-ons and applications have been written for it.

A few basic things to know about the ESP module:

• It is a 3.3v chip. It does not tolerate higher voltages well, even for short periods of time. Before connecting to an ESP module, verify that your voltage is 3.3v or the chip may be damaged as soon as power is applied.

• It is power-hungry: it generally requires 250-300ma of current during operation. If the available current drops out of the required range, the ESP module generally disconnects from any network connection; afterwards, it does not reconnect on its own and usually must be restarted.

• It usually connects to an access point or wireless router rather quickly, but if it can't find one within 4-5 seconds, it generally gives up trying and power-cycling the unit is about the only way to restart it.

• Several manufacturers produce modules that incorporate the ESP8266 chip; not all are the same. For example, some may provide two LEDs on the module, one for power and one that monitors the TX line while other manufacturers may use only one LED that serves both functions. Therefore, the LED display from one can appear completely different than another, leading you to believe the module may not be functioning properly when it's perfectly fine.

• The modules are relatively easily damaged by static electricity, power surges or rough handling. Plugging a new module into a live circuit is generally not a good idea.

• As they are quite inexpensive (<$2 each) having several replacement spares is a good idea, especially for an experimenter. Virtually all of them are manufactured in China, so allow for adequate delivery time.

• The modules use an external flash memory chip which is key to the operation of the ESP8266 chip. Users have experienced problems with modules manufactured with the PUYA memory chip. The symptoms are that either one can't connect to the chip or that the chip's SPIFFS memory cannot be used, which may be a requirement for some versions of custom ESP firmware (such as the ESPixelStick firmware).