Extension Board

The extension board is designed for being plugged onto the base board. It allows using a variety of sensors such as air pressure, humidity and temperature, as well as displays, gas meter, etc. A buzzer my be connected as well for alarm output.

You can also experiment with the extension board when using it standalone, ie. without eBUS connection. This makes it easy to connect sensors or displays to the Wemos.

Construction

extension

The number of components is a lot less compared to the base board and it consists mainly of female and male headers for connecting Wemos, displays, and sensors.

The power is supplied directly to the C-connector of the Wemos via a USB power supply.

Circuit Diagram

Circuit diagram exten board
Older versions are here: v2.1 v2.0

Part List

The necessary parts are listed here.

Assembly

The board is not lead free manufactured (HASL), so it can be soldered with normal leaded solder. This is still legally allowed for private use as well as partly for commercial purposes.

The assembly of the extension board is carried out just as the base board according to usual rules, i.e. flat components first followed by the higher ones in layers as follows:

  1. SMD switch (only for v2.0)
  2. Resistors
  3. Flat sockets
  4. Capacitors
  5. Switch
  6. Socket headers
  7. LEDs
  8. Pin headers on the back for plugging onto base board
  9. Plug in the Wemos D1 with its pin headers

Before soldering the resistors, be sure to check the resistance values with an ohm meter to avoid misplacing them.

Important hints for version 2.0:

Important hints for all versions:

Assembly variants

The possible application variants are described here.

Depending on the desired application many assembly variants are possible. In particular, one should consider before soldering, whether and how for example BME280, OLED, Nextion, gas meters, NTC, Buzzer, etc. are to be connected.

If, for example, a BME280 is to be used outside the housing for measuring temperature etc., a 4-wire cable is required which is connected via a pin header, socket header, or directly to the extension board. Depending on this, the corresponding socket and/or pin headers have to be selected and soldered.

The jumper assignment depends on the variant used as well.

Assembly of LEDs

See base board.

Soldering the extension board

Assembly
Assembled and soldered board (v2.0).

Final
View from the back (v2.0) with jumpers and pin headers for connection to the base board.

Finished extension board

Final
That’s how the finished extension board (v2.1) looks like when plugged onto the base board including Wemos with ESPEasy and directly attached BME280. On the left is the Dupont cable for the connection to the Wemos with ebusd-esp.

Jumper Function Matrix

Jumper
Older versions are here: v2.1 v2.0

On the back of the extension board there are some jumpers (solder bridges) that allow different assignments depending on the desired sensors or used Wemos firmware.

Depending on the desired application variant for the extension board, the jumpers have to be taken care of as otherwise the sensors won’t work.

Important: The Wemos with ESPEasy may not be jumpered to RX and TX, as otherwise the signals from the simultaneously connected Wemos would be grounded with ebusd-esp!
Such errors may not seem to make any difference at first, but certainly show up once several devices are connected to the eBUS.

Jumper für Version 2.2

Sensor Wemos PINs SJ2 SJ1 SJ4 SJ3 Comment
ebusd-esp RX/TX     3-2 3-2 only for using ebusd-esp directly on the extension board!
ebusd-esp D5/D4     2-1 2-1 only for using ebusd-esp directly on the extension board!
ESPEasy       open open  
JP6 BME280 D1/D2          
JP7 Buzzer D0          
JP3 OLED D1/D2          
JP2 Nextion D8/D7 3-2 3-2      
JP2 Nextion RX/TX 2-1 2-1      

Example 1: in case a Wemos with with ESPEasy and a BME280 shall be connected, no jumpers have to be set.

Example 2: in case a Wemos with ebusd-esp shall be used directly on the extension board, the jumpers SJ4/SJ3 have to be connected as stated in the table.

Jumper for version 2.1

Attention: the layout of SJ8+SJ4 is wrong, as the originally middle pin is placed on the right!

Sensor Wemos PINs SJ8 SJ4 SJ7 SJ3 SJ6 SJ2 SJ5 SJ1 Comment
ebusd-esp RX/TX         2-3 2-3 2-3 2-3 only for using ebusd-esp directly on the extension board!
ESPEasy               open open  
BME280 D1/D2 3-1 3-1              
BME280 D3/D4 2-1 2-1              
Buzzer D0                  
OLED D1/D2 3-1 3-1              
OLED D3/D4 2-1 2-1              
Nextion RX/TX     2-1 2-1          

Example 1: in case a Wemos with with ESPEasy and a BME280 shall be connected, the jumpers SJ8 and SJ4 both have to be connected on pin 3 and 1 and the jumpers SJ5 and SJ1 remain open.

Example 2: in case a Wemos with ebusd-esp shall be used directly on the extension board, the jumpers SJ6/SJ2 and SJ5/SJ1 have to be connected as stated in the table.

Jumper for version 2.0

Attention: the label on SJ2+SJ1 is exchanged, so SDA+SCL are on the top (not on the bottom)!

Sensor Wemos PINs SJ2 SJ1 SJ3 SJ4 SJ5 SJ6 SJ8 SJ7 Comment
ebusd-esp RX/TX         1-2 1-2 1-2 2-3 only for using ebusd-esp directly on the extension board!
ESPEasy               open open  
BME280 D1/D2 1-2 1-2              
Buzzer D0                  
OLED D1/D2 1-2 1-2              
Nextion RX/TX     1-2 1-2          

Example 1: in case a Wemos with with ESPEasy and a BME280 shall be connected, the jumpers SJ2 and SJ1 both have to be connected on pin 1 and 2 and the jumpers SJ8 and SJ7 remain open.

Example 2: in case a Wemos with ebusd-esp shall be used directly on the extension board, the jumpers SJ5/SJ6 and SJ8/SJ7 have to be connected as stated in the table.

Jumpers when fully equipped

Assembly

This image shows a variant with full configuration: the base board with Wemos ebusd-esp, the extension board with ESPEasy and a BME280 sensor for temperature, humidity, and pressure.

In this variant no jumpers have to be set for the Wemos with ebusd-esp, since it is attached to connector JP8 and this directly has both, the RX and TX signal.

The Wemos with ESPEasy is plugged onto the expansion board and thus uses all the pin headers provided. If ESPEasy is located on the extension board and is connected to the BME280 sensor, no jumpers (v2.2) or jumpers SJ8/SJ4 (v2.1) or SJ2/SJ1 (v2.0) have to be set.

Jumpers fully equipped for version 2.2

For version 2.2, no jumper has to be set for the fully equipped variant described above and the I2C settings on ESPEasy can remain on default (D1/D2).

Jumpers fully equipped for version 2.1

Sensor Wemos PINs SJ8 SJ4 SJ7 SJ3 SJ6 SJ2 SJ5 SJ1
BME280 D3/D4 2-1 2-1            
OLED D3/D4 2-1 2-1            

Attention: With these jumper settings for v2.1, the I2C settings on ESPEasy have to be changed to D3/D4.

Jumpers fully equipped for version 2.0

Sensor Wemos PINs SJ2 SJ1 SJ3 SJ4 SJ5 SJ6 SJ8 SJ7
BME280 D1/D2 1-2 1-2            
OLED D1/D2 1-2 1-2            

With these jumper settings for v2.0, the I2C settings on ESPEasy can remain on default (D1/D2).