Redkea: easy to use Android app builder for IoT


Today I have some interesting stuff on my desk. I have just received one ESP8266-EVB board from Olimex, one of the cheapest ESP8266 boards in my collection (I paid for it just a bit over 13 EURO).

Before we begin, let’s take a close look at the board.

The ESP8266-EVB has one relay, one button and two expansion connectors. Board power is 5V only, a nasty choice as the board has the same power connector as the Arduino boards, so it’s easy to mistake and use the wrong power adapter. Considering the SY8009 used in the power supply, the maximum voltage that can be applied is 6V. Anything more than this and the board will release its magical smoke.

There’s also a connector for the MOD-WIFI-ESP8266-DEV module. Good thing, I can take out the ESP8266 module and program it separately. In the documentation of the ESP-8266 board, the board has to be powered from 5V while using a 3.3V FTDI to do the programming. I consider this approach too complicated, and I prefer to make my own programming rig.

ESP8266 programming rig

ESP8266 programming rig


Here, I use one USB-UART click from Mikroelektronika to do the programming and also to supply 3.3V for the MOD-WIFI-ESP8266-DEV module. Connections are as follows:

  • USB-UART 3.3V   – MOD-WIFI-ESP8266-DEV pin 1
  • USB-UART GND  – MOD-WIFI-ESP8266-DEV pin 2
  • USB-UART RX      – MOD-WIFI-ESP8266-DEV pin 3 (GPIO1, TXD)
  • USB-UART TX      – MOD-WIFI-ESP8266-DEV pin 4 (GPIO3, RXD)
  • MOD-WIFI-ESP8266-DEV pin 21 (GPIO0) has a button connected towards GND, with a 10k pull-up resistor.

To program the board, one must keep the button pressed while applying power (plugging in the USB cable) and release it after the board is powered on.

In Arduino IDE, one should set the board to Generic ESP8266, with 2Mb FLASH and 57600 baud for serial connection.

ESP8266 - Arduino IDE settings

ESP8266 – Arduino IDE settings

Now, we can upload a simple test program that turns the relay on and off (the relay is connected to GPIO5).

Program the module, remove it from the breadboard and put it back into the ESP8266-EVB. Apply 5V power to the board. If everything is OK, you should hear the relay clatter, and the green LED led will turn on and off with the relay.

We are now ready to go to the second part of this blog post, and we will create a smartphone app to turn the relay on and off remotely.

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