Bed of Nails Programmer

    1. Every once in a while, you brick a unit. When that happens on a Tuya based product, this fixture can help you out. It is essentially a bed of nails test fixture which is designed to be held in place over the top of the Tuya TYWE3S module found in an array of low cost Chinese IoT hardware. There are three 3D printed parts: An outside guide which fits snugly around the sides and base of the wireless module. Once place it is the point of reference for the needles.

    2. A piston which holds two rows of spring loaded test needles. These are spaced to touch down on top of the castellated connector edge of the wireless module. It is possible to load needles to touch all sixteen pads though in practice only nine are needed to ensure programming.

    3. A simple clip to hold the two above pieces together. I used the shell and piston several times without this clip but it does keep the fixture from falling apart when not in use.

Source models are provided for the three mechanical components.

NOTE - These models where tweaked to work with a MonoPrice Inventor II. It does a really poor job holding the small holes needed to hold the pogo pin sockets and the clearances of the sliding parts. As a result, you will most certainly need to re-tweak the models. Being an FOSS bigot, I use FreeCAD for my 3D designs. Full models for each part are provided at the bottom of the page. What is not provided are output mesh files, such as step or stl, I'm providing the source file so you have them when you will need to tweak, generate your print files after you look at the models.

This was designed with "P50" test pins and R50 receptacles in mind. These are cheaply and readily available in Asia and on sites like AliExpress. The spring is a standard hardware store 1/4" by 1" spring, normally at a hardware store but never at Home Depot or other big stores.

I am in the process of adding support for this module in the ESPTOOL Python program. I have forked the official project on github here, at present you are better off using the official repo.


    1. There is a small cutout below the middle edge of the "piston" so that you can add epoxy to hold the receptacles in place. I did not capture documentation when I was building my assembly but would welcome anyone who builds this sending me images of their glue step and I can post them for others.

    2. I did not know it at the time, but this tool is essential for programming battery operated sensors which shutdown partway through the Tuya-OTA over air process. Visit for one person's fun trying over the air updates for these devices.