The Wio Tracker L1 Meshtastic Communicator

Background

This is my first project, but I'm not here by chance. I started it because I wanted a communication device for my son that didn't require any built-in infrastructure or additional devices. That's how I found the Meshtastic network, exactly what I need.

I looked at the list of supported devices, and I liked the Lilygo t-deck the most, but I didn't want a color display. Plus, the GPS-capable T-deck is expensive for me. Browsing further, I saw the option in the seeedstudio Wio tracker L1 family. All I need is a qwerty keyboard. I found existing projects for this too using the CardKB v1.1 board. I ordered the necessary parts on August 24th.

I joined the seeedstudio discord channel looking for clever ideas, and that's when I found the hackster.io challenge. I like challenges like this because the deadline motivates me, and I'm already in flow anyway. I registered on August 26th.

I'm a structural engineer in my private job. First I had to free myself up, only then could the new project come.

The power supply will be provided by a 18650 lithium battery, because it is easily replaceable and standardized. This also determines the minimum thickness of the device. I figured that I could best utilize this thickness with a foldable device.

3D design to proposal

These images were exported from a raw CAD file. The case still needs to be opened to install the devices.

Preface to the rest of the article

When I was able to take the time to work on the project, I always got into the flow, enjoyed the work, but unfortunately I didn't manage to finish the final version by the deadline. The battery connector and the cable routing can still be improved. And I have to rethink the look of the keyboard, because it won't be possible to make a usable print out of it. It's just a matter of time, but I will finish the device. In the meantime, I'll share the files with the community, in case it gives someone a good starting point.

The competition continues

I managed to make it to the top 10. Thank you for the supportive comments, they mean a lot to me!

On September 16th, my package arrived, which included a Wio Tracker L1 Pro and a XIAO nRF52840 & Wio-SX1262 Meshtastic Kit. I started to get acquainted with the Meshtastic system. Fortunately, many radio amateurs operate fixed nodes in my area, so the coverage is quite good. It was a pleasant surprise that messages came from 70 km away.

I bought the XIAO & Wio Kit for testing. It currently lives in a Kinder Egg capsule, but a proper house is already being planned for it, paired with 18650 batteries.

Hardware

The case I submitted for the competition was good enough to show the broad outlines of my idea, but it wasn't yet suitable for printing. I had to further develop it to make it mountable.

First I designed the keyboard module. I had to make sure that the CardKB connector and the cable would fit in the thin housing. I didn’t anticipate that the cable plug would stick out so much and the cable would take up so much space, so I had to increase the dimensions in this area.

I tried to solve the fitting with as few screws as possible. To do this, I designed small tabs on the right side of the cover. I thought about three versions for the buttons:

• Make the CardKb visible: this is the simplest, I found an example, but it is not aesthetic, so I discarded it
• Print it in plastic: sticker or recessed characters?
• CardKB silicone cover: this is the most beautiful, but shipping is expensive for me. (I may make a version for this later)

Finally, I developed the printed version with recessed characters.

The Wio Tracker L1 housing could have been next. There was plenty of space in this part. However, since the connectors and buttons are located on the left side, I had to align the electronics to the left side. The plan is to place the GPS antenna and the flat antenna of the XIAO & Wio Kit in the remaining space. When I first folded the model, I was faced with the fact that the large protrusion of the keyboard connector already reaches the housing, so I sunk this part a little. In addition, the solar power port is also located here on the Wio Tracker PCB, so I thinned the wall thickness here to accommodate all the components. The 18650 battery also belongs to this part, but here I only got as far as the battery and some connection options at the ends could fit in the housing.

First print

I don't have my own 3D printer, but there are several people in my city who do contract printing. My goal was to see how the PLA printed case works in real life. There are some lessons learned:

• although the printer is accurate to 0.05 mm, in reality even 0.1 mm of free space is not enough for the hinges.
• The keyboard could only be printed vertically, because when printed horizontally it stuck to the support material.
• However, when printed vertically, the 0.1 mm of free space was not enough for the keys to move freely.
• I can't design a wall thickness of 0.3 mm, because they couldn't print it, and the case ended up with holes.

I was able to put the case together by force, the components fit, but the cables need more space.

Based on the experience, I continued the design. I considered the keyboard problem to be the most urgent, so I made test prints for it. In the end, I had to leave a 0.4 mm gap next to the keys. At this point, I thought about switching to Resin instead of PLA, but I couldn't find a suitable partner in town for this. PLA remains.

I widened the housing by another 4 mm so that the Grove cable routing would take up less space vertically on the edge of the keyboard. This modification also helped to make more space for the cables routed in the hinge, and thus the Wio Tracker housing no longer needed to be recessed.

Meanwhile, I realized that the GPS antenna cable is very short, so I either stay with the original layout and place it above it, or place it close to the pcb. In the end, I chose this because it does not require further increasing the size of the housing.

The antenna fits glued to the inner edge of the housing. However, the experience of a few weeks made me realize that an external antenna is much more efficient. I planned a version with an external antenna later anyway, the need also came up in the comments. I changed the concept a bit and redesigned the housing using the external antenna of the Wio Tracker Pro. The battery contacts became M2 screws.

Final parts list

• Wio Tracker L1 Pro OLED (GPS+ external antenna)
• M5Stack Unit CardKB v1.1 (20 cm Grove cable incl.)
• 18650 Li-ion battery (3500 mAh)
• M2-6; M2-10 screws
• JST PH 1.25 plug (with 15 cm wires)
• 3d printed PLA