Nmea4Wifi (2021) - SMD, TH and KIT Upgrades

Discussion and support for the Nmea4Wifi multiplexer - a 4-input Nmea 0183 wifi multiplexer.
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Luis Sa
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Nmea4Wifi (2021) - SMD, TH and KIT Upgrades

Post by Luis Sa » Wed Feb 17, 2021 8:49 pm


From 2020 to 2021 the Nmea4Wifi multiplexer has gone through significant improvements. The main modification is the use of faster optocouplers. In this post I describe the technical details of the present multiplexer. Normal users do not need to read this as everything concerning the operation of the multiplexer is described in the acknowledgement webpage that you see when you type on the navigation bar of your browser.

The multiplexer is available in versions built with SMD (Surface Mounting Devices) and TH (Through-Hole) technologies. So I am using 3 designations:
  • Nmea4Wifi SMD
  • Nmea4Wifi TH
  • Nmea4Wifi KIT
All versions are identical in terms of functionality and software. The TH and KIT versions are also identical in terms of hardware. The obvious difference is that the KIT version is assembled by the user. In all versions you can use a USB cable to receive and transmit data from and to a computer. This USB cable can also power the multiplexer so that you do not need to supply 12V to the multiplexer. Both the USB cable and the 12V supply from a battery can coexist. If you use an USB cable the top cover box can not be used, except if you cut an hole on top cover in the case of the SMD version. Also note that the SMD version uses a mini USB type B socket strongly soldered to the PCB. All versions use spring type connectors.


The circuit diagram of the multiplexers can be downloaded from the links at the bottom of this post.


The remaining part of this post is addressed to the builders of the Nmea4Wifi KIT. Kits are supplied with the original Instruction Manual for the Nmea2Wifi multiplexer. We advise you to read that manual as there are many common aspects between the Nmea2Wifi and the Nmea4Wifi Kits. Basically the Nmea4Wifi kit uses a different processor. Instead of the ESP8266 module, the Nmea4Wifi kit uses either the ESP32 MH-ET module or a custom ESP32 module.


The custom module is now ready and will replace the MH-ET module. The 20 pins of the custom module correspond to the inner 20 pins of the MH-ET module


In the following we show the relevant differences to the referred to Instruction Manual. The parts list is as follows:


The PCB (Printed Circuit Board) and the some parts in this KIT (voltage regulator and resistor arrays) are shown in the following pictures



Note that the diodes, LEDs, type A resistor arrays and ICs need proper orientation. The diodes have a bar that indicates the cathode. You need to insert them so that the bar that exists in the body of the component coincides with that shown on the PCB. The LEDs have 2 terminals (anode and cathode). The cathode terminal wire is shorter than that of the anode and should go on the hole that is next to the connectors. Resistor arrays R2 and R3 have a dot printed in their bodies. The pin near these dots should go on the holes whose pads are quadrangular. Resistor array R1 can be mounted either way. As for the ICs please follow the indications on the referred to Instruction Manual. The following pictures will also give you some ideas on how to assemble ther KIT.


Finally note that you need to use the Arduino IDE to flash the ESP32 module with the small sketch as described here. Then you can update to the latest firmware using OTA (Over The Air). If you are not familiar with the Arduino IDE you could contact me before buying the KIT to check if I can send you a pre flashed module.

Regards, Luis
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