(this post refers to the KIT and the TH (Through-Hole) version of the NMEA2WIFI supplied from mid 2020 to February 2021. A new optimization was performed as described here.
This post is mainly dedicated to the users that build the NMEA2WIFI kit. In order to simplify the hardware I designed a different circuit board. Resistors R1 and R2 have now an identical value of 1K5 but any value from 1K to 2K2 could be used. Resistors R3 R4 R5 and R6 that appear in the "NMEA2WIFI KIT" leaflet were replaced by a single 8 pin resistor array of 330 ohms. Also instead of 2 100nF ceramic capacitors and 1 100uF electrolytic capacitor, the new design now uses 4 100nF ceramic capacitors and a 10uF electrolytic capacitor.
Note that in relation to the leaflet that is supplied with the multiplexer, the new PCB has a recess to allow an easier entry of the wires and that the power socket (+12V and GND) is on the left. You should identify the +12V and GND connector pins using the labels that you see on the PCB that you receive and not the ones you see on the leaflet. Also note that the color of the PCB could be different. In this post it is red but it could be green or blue. Whatever the color the circuits are identical. The same applies for the colors of the screw connectors.But the main difference is the that the multiplexer now uses a dual channel optocoupler, the HCPL-2731, instead of the 2 single channel 6N139. The schematics, referred to as NMEA2WIFI2731can be obtained here and the PCB is shown in the following picture
and the assembling of the components is illustrated in the following pictures: