For my journey into Meshtastic one of the most frustrating aspect has been the polarity of JST connectors. Many of the Meshtastic components use small plastic JST connectors as a standard, whether its LiPO batteries, charge controllers or Meshtastic boards such as my RAK Wisblocks. While it seems like the choice of using a JST connector for this application is ubiquitous there is no standard pinout for polarity of these connectors. In fact, RAKs documentation makes this polarity abundantly clear. To make this matter worse most components do not offer simple reverse polarity protection leading to many fried boards.

To make this matter even more frustrating is the fact that most common JST pigtails available on Amazon or Aliexpress seem to have a polarity that is opposite of most of the common Meshtastic component JST connector polarities.

Figure 1. Charge Controller – LiPo – Incorrect Polarity

For my first RAKwisblock board I made a quick attempt to desolder the onboard JST connectors. My plan was to simply flip them onboard by 180 degrees. This was a frustrating task as even after removing the solder between the board and the contacts the connector proved to be difficult to remove. Upon further inspection it appears that RAK uses adhesive to help make this connector more rigid. This initial solution proved to be not a good fix.

Figure 2. RAK Wisblock – JST Cable – Incorrect Polarity

A few nodes later I came to the conclusion that the best solution to this problem is to simply re-pin the JST contacts. This can be easily done by gently lifting the plastic connector housing contact locking bar while giving the wire a slight tug. When doing so you need to lift the locking bar so that the locking tang on the contact itself can slip past it and out of the connector housing. While performing this work use care as to not break the plastic retainment bar.

Figure 3. Contact Extraction

Figure 4. Re-pinned JST connector with the corrected pinout

After you have completed re-pinning the connectors, take a moment to double check your work. I recommend when purchasing new Meshtastic components to immediately re-pin all of the JST plugs immediately after getting new components, this will help avoid inadvertently connecting devices with the incorrect polarity and releasing the “magic smoke”.

’73!