Not sure if others would have interest in this, but I'm designing a PCB for an easy-to-solder TH node. As presently conceived, it would have 3 surface mount components (an LED on the front and a resistor and capacitor on the back), plus a DIP atmega328p, a header to accept an inexpensive si7021 TH breakout board, an FTDI header, and an RFM69HW. The idea is that it would run at 8Mhz and be powered by two AA batteries, so it's sized to be compact but still easy to solder. The same thing could be achieved with wires and some of the other boards out there, but this might be a little tidier if a TH mote is what you want as either the starting point or the end-point.

PCB dimensions are 0.65x2.55 inches. i.e. it is narrower than a typical AA battery holder, but roughly the same length.

The LED and resistor are optional, and you could forego the capacitor as well if you wanted a truly bare bones TH solution. However, the pads are there if you wanted to utilize them. Also, you could skip the si7021 BoB if you wanted just a generic mote.

I had hoped that someone would make an easy to solder board like this for the RFM69HW, but I got tired of waiting and finally decided to just make my own.

I found a good place to do range testing.... too bad I didn't bring the gear!

@OldSurferDude If I have a question about something I generally post the question. Sometimes someone will answer it, and all is good. But on those occasions where no one answers it to my satisfaction, and I later do figure it out myself, then I return and post the answer to my own question. I think if everyone followed this protocol, it would help. What I see across forums (not just mysensors, but just about all forums everywhere) is people who post questions with a "Thanks in Advance" attitude, but who never bother to close the loop if they do find the answer. Or they never confirm whether or not someone's suggestion worked or didn't work. The result is that when searching for an answer, one has to search through a lot of posts which don't contain any useful answers. So, I would encourage everyone to return and post answers to their own questions, if no one else already has, because in all likelihood someone else will have the same question in the future. I think that one small change might make a huge difference.

Good news! Last night I did some accelerated load testing on the supercap. First I charged it to 3.6v and then I hooked up an RFM69HW mote which woke up once a second to do 3 things: 1. check the voltage level, 2. turn on an LED for 1ms to simulate a sensor load, and 3. transmit a packet containing the voltage data using the RFM69HW.. Bottom line: 14,111 packets transmitted before running out of juice.

Not bad for a first attempt. :)

Yesterday received the PCB. Today assembled for testing this battery-powered nRF52-based passive infrared motion detector:

Made this 12 button keypad. Requires only one analog pin to read which button is pressed, and any button press can also wake an arduino from sleep:

Consumes no power when no button is pressed.

For sure, the store shelves are pretty much overflowing with smart home products and IoT these days, much more than in the past. Is it just diffusion of attention, or do people just buy what they need now in complete systems or something? Or buy stuff that has phone apps instead of a hub? Or has Home Assistant taken over? Or Amazon Alexa? Not much in the way of new postings compared to the past. If anything, I thought there'd be more activity due to more and more IoT interest generally. If anything, it seems like Mysensors has a more robust and complete system now than in years past, and it's broad enough to include just about everything. What gives? Have off the shelf prices dropped so far that the economics no longer favor rolling-your-own or something? i.e. buy rather than build? Where's the new frontier? Is it now AI and system level stuff? I'm really curious. I mean, not all that long ago Google bought a thermostat company (Nest) for over a billion dollars. There's clearly been a sea change, and I'm just wondering what changed.

A pair of lithium AA primaries is hard to beat because:

1. Unlike alkaline's, they don't leak.
2. Have a look at the discharge curve: https://data.energizer.com/pdfs/l91.pdf By the time they drop to 2.4v, if not before, you'll want to replace them.
3. Obviously much longer life, both shelf life (20 years!) and energy capacity.

I think running 8Mhz from the internal RC is a no-brainer: wake up time is less than 4us. So, if your node wakes up often, you'll save a ton of energy over time.

The best time to take your battery measurement is immediately after a Tx. That will give you the most conservative reading. Save that measurement in a variable and then send it in your next transmission. Switch on your ADC just before Tx and take your first ADC measurement during Tx, because you have to throw out the first measurement anyway. That way you can take a fresh (and valid) ADC measurement just after Tx before the voltage rebounds.

Hope that helps!

Here's the version that I most recently assembled:

As you can see, the 15F supercap is now on the board itself. It works fine.

I've since made a few refinements and have sent the new files off to be fabbed. The newest version of the PCB will measure roughly 22mm x 22mm.

Put together this pro mini nRF24 shield for testing...

I have a number of sensor projects that sit within the nice footprint of a Pro Mini. Now I want to find a kind of universal power platform--hopefully small--to power them. So far, what I came up with was this, which runs the Pro Mini from 2xAAA batteries, and where the Pro Mini (and whatever the project built on it) simply "plugs in" to it:

Is there anything better? Ideas? Comments?

It worked! After doing the above mass erase, the nRF52832 Ebyte Module successfully programmed from the NRF52 DK. I uploaded the mysensors lightsensor sketch, and the serialGateway running on the NRF52 DK is receiving its messages. :)

Many thanks to mfalkvidd for his mass erase suggestion and for his link to the Roger Clark youtube video, which had further mass erase commentary.

Also, many thanks to d00616 for his excellent guide:
https://www.openhardware.io/view/376/MySensors-NRF5-Platform
Without that, I would have been lost on how to set anything up.

Thanks to everyone else too who made comments and suggestions. This has been a great group effort with a successful outcome. :) :) :)

FWIW, I received this micro-USB test board from PCBway today:

As you can plainly see, it appears they had no difficulty fabricating the plated slots. In fact, they didn't even flag it as a possible issue.

This thread is intended to be a collecting point for all information related to nRF52840.

It turns out the nRF52840 dongle is very easy to solder with pin headers, and the format is breadboard friendly as well:

@madscientist Not to throw cold water on the idea, but why is it needed? Aren't there already enough SBC's around, like the Pi for instance? There's a lot to choose from that are already finished. What makes this stand out from all the rest?

My wine rack is at the store. ;)

I read somewhere that China calls the SI24R1 their "domestic" radio. It's a clone of the nRF24L01, but I like it better because it has a Tx power of 7db rather than the anemic 0db of the nRF24L01. Costs about 50 cents per chip, which makes it a reasonable compromise over opting for something cheaper but less compatible. If you haven't seen it, Ebyte has a parallel line-up that uses it (it's nice that they're careful to separate it out onto different modules from the real mccoy):

(source: https://www.ebyte.com/en/product-view-news.aspx?id=1304)

Worthy of note is that the range with the SMA-K connector is so much better, assuming their chart is accurate. I mean 2500m as compared to 800m for the same 20db Tx?

Also pretty cool now is that ebyte shows the current traces for tx, rx, and sleep on their modules, so it's easier to directly compare the SI24R1 clone modules to the real thing:

For this project box that I'm making (actually printing it as I type this), I found an easy way to add ventilation: use a hex infill and turn off the upper and bottom layers.

As you can see, it can still have standoffs for screwing down a PCB and for securing a lid.

Here's the finished unit:

What it does is completely eliminate the audible PWM noise from the fan on the Prusa I3 MK3. Now it can run practically silent. :)