Dogfooding the ManT1S

Wikipedia says that "’dogfooding’ is the practice of using one’s own products or services. This can be a way for an organization to test its products in real-world usage using product management techniques." I’ve always tried to do this before releasing something. By using something yourself you can figure out pain points, things that don’t work well, or at the very minimum areas of friction, before your customers find them for you.

This happened while I was working on the PIR floodlight demo for the campaign video, it exposed an issue with how to inject power and apply termination to the network once you have turned every node into a nice self-contained module.

What Is Termination, and Why Is it Needed?

When waves crash against a wall, they bounce back to where they came from. When a guitar string is plucked, it keeps ringing because both ends are stuck and bounce the wave back into the string, producing a standing wave. This may be great for making music, but it is a problem if you’re trying to send a single wave containing data through a medium, such as a wire. You don’t want old data to keep ringing in your wire while you’re trying to send new data!

To prevent this, you need to terminate your transmission line so the wave gets absorbed at each end. Doing this is called "termination". Regular Ethernet does this inside every device, and can get away with that because Ethernet connections are always point-to-point with one device on each end of the cable. So you don’t need to think about it: it’s always done for you.

A T1S mixing segment on the other hand can have multiple devices (up to 8 officially) in a chain, and only the nodes at the end should terminate the transmission line, not the ones in the middle. So, this is something you, the ManT1S user, need to take care of.

Termination on The ManT1S

There are two ways to enable termination on the ManT1S. The first one is closing the JP1 and JP2 solder jumpers on the top side of the board:

The second one is shorting both sides of the JP3 jumper on the bottom:

This second way is mostly intended for if you are surface mounting a ManT1S onto a carrier board and you want to export the termination selection to your own board. The footprints I intend to release will have pads to connect to the pads of JP3 for this purpose.

Termination on the ManT1S-Bridge

On the ManT1S-Bridge, you can enable termination by having jumpers JP1 and JP2 (the two that are together) closed:

The Issue I Ran Into, and the Solution

The PIR sensor demo I made for the campaign video was based on a ManT1S and a Sparkfun Qwiic PIR sensor, connected together with a Qwiic cable. All nicely integrated into a 3D printed case:

But this exposed a problem: the only thing externally accessible to this module is the screw terminal for the T1S network. So how do I terminate the network if this is the last device in the chain? Do I have to open the case to solder the termination jumpers? Sure would be convenient if I could just connect termination externally instead.

And what if I wanted to apply power for the mixing segment at this node? Do I now have to crack open the case to connect power to the ManT1S, so it can be properly applied to the network through filter inductors? Those screw terminals sure look nice for connecting power! (And that’s what I accidentally did when shooting the campaign video and it seemed to actually work—but not recommended! :))

It kind of goes against the whole idea of modularization if every time you make a change to the network topology, you need to modify the node depending on where it is in the network and whether you might want to apply power there or not. Wouldn’t it be nice if there was a little gadget you could use to properly apply power to the mixing segment, or network termination, or both?

Well now there is: enter the ManT1S-Gadget:

This little board can inject power with proper filtering, or you can enable termination with the JP1/JP2 jumpers bridged, or you can do both if this is an end node that also injects power. Without needing to use a whole ManT1S to do it right! It’s pretty much just the electrical interface to the network, broken out on a tiny board by itself. So now you can keep your ManT1S nodes nice and generic, only expose their T1S interface, and deal with power injection and network termination externally!

The next question is: how can you get one? Will this be offered as a new campaign reward? No, even better: we’ll just add one of these to every Starter Kit as a freebie! So if you’ve already placed an order for a kit, you don’t need to do anything, it will just be included when your reward ships!

You are welcome! :)