Warning: do not connect the DHT11 temperature sensor as indicated in the eBay pictures, it is the wrong way around and will fry your board!
I’ve just received my ESP8266 development/SDK board in the post and am now starting to try and work out what everything on it does.
I have managed to connect to the board using the on-board USB to Serial interface (CH340 chip).
Plugging in to the USB mini port seems to power the board through the on-board 3.3V Voltage regulator (AMS1117 3.3) and the red LED on the ESP8266 daughter board itself powers on, along with a red LED on the main board.
Plugging in to the USB micro port, however, doesn’t appear to correctly power the board. Both of the same LEDs come on, but slowly fade out over a couple of seconds.
The CH340 drivers seemed to automagically install on Windows 8 and create a new COM port. I wasn’t able to send AT commands using Putty and believe that there are some versions of firmware which don’t like Putty, so I used Coolterm instead and was able to connect on COM8 (check in device manager for which COM port gets assigned) and at baud rate 115200. Sending some AT commands seemed to work fine and I was able to connect to my home WiFi network and then ping the device.
Below is a screenshot of Coolterm with NodeMCU installed on the ESP8266 and running some custom lua code to serve a webpage and switch the relay.
Additionally, there is an on-board 10k potentiometer which appears to be connected to the ‘ADC’ pin on the ESP8266 although currently I don’t seem to be able to read this as a variable input.
The switch controls are as follows:
- R – RGB LED Red to pin ‘IO15’ (must be on to boot to application mode)
- G – RGB LED Green to pin ‘IO13’
- B – RGB LED Blue to pin ‘IO12’
- W – White LED to pin ‘IO14’
- J – Relay coil to pin ‘IO16’
- B – Buzzer to pin ‘IO5’
- K1 – GND to pin ‘IO15’ (same as Red RGB LED – holding ON while powering is same as R off i.e. will not enter application mode)
- K2 – GND to pin ‘IO0’ (Same as S2 – switch ON when powering to enter reprogramming mode)
- S2 – GND to pin ‘IO0’
- S3 – GND to pin ‘IO2’
For the board to boot correctly into application mode, it looks like the DIP switch ‘R’ has to be On, which pulls pin IO15 high. To enter reprogramming mode to reflash the ESP, K2 must be On or switch S2 can be pushed.
By default (at least in the firmware that came with the board and the latest NodeMCU firmware) most of the pins are configured as inputs, which causes them to float or be pulled high and so with the DIP switches ON the RGB LED elements are all lit, the white LED will light, and the Relay and green indicator will be on. IO5 does not have this behaviour so the buzzer is off by default.
I notice that the images from Ebay (above) show the DHT11 to face outwards, but this actually appears to be incorrect as the pinout is the opposite, and so the DHT11 should be inserted facing inwards. Apart from this, it seems to be a pretty well produced and reasonable quality board.
There are more bits of useful information on this version of the ESP8266 board itself over at http://blog.squix.ch/2015/02/esp8266-esp-201-breakout-board-review.html
Many thanks to jwbr who has created a schematic of the board here: http://www.bpower.nl/