@DenisJ Are you measuring a USB device? Look at something like this https://www.aliexpress.com/item/33019457512.html?gps-id=pcDetail404&scm=1007.16891.96945.0&scm_id=1007.16891.96945.0&scm-url=1007.16891.96945.0&pvid=824c24fa-034b-4801-b51d-50b2ad877945&_t=gps-id:pcDetail404,scm-url:1007.16891.96945.0,pvid:824c24fa-034b-4801-b51d-50b2ad877945,tpp_buckets:668%230%23131923%2330_668%230%23131923%2330_668%23888%233325%239_668%23888%233325%239_668%232846%238110%231995_668%232717%237561%23332__668%233374%2315176%2335_668%232846%238110%231995_668%232717%237561%23332_668%233164%239976%23761_668%233374%2315176%2335

(AliExpress: Cheap prices and one could question the quality, but for the most part they work. Shipping takes about a month. rarely faster)

I, too, am a "gray hair" (if I had hair). I despise cloud dependent devices. The reasons are many. ISPs, despite what they say, are not reliable. ISPs are so close to be monopolies, that they act like them. Your ISP can, and will, prevent access to the cloud if they have a competing product.

The manufacturers of cloud dependent devices, sell your information and statistics on how you use the devices. This is how they make money. When one of these manufacturers goes out of business, the company that buys up the IP continues to sell that information and ceases the little support that one did get.

I might be getting a little paranoid here, but I'm pretty sure there is unrelated-to-function software (spyware) incorporated into many products. (In the late 90's, the company for which I worked resisted the temptation to do so, despite heavy pressure from marketing.) I call it "ET phone home" Maybe the software is innocuous enough, but it can be hijacked by bad actors.

There is another problem plaguing home automation and that is poorly designed and poorly documented (which leads to pathetically supported) hardware and software. More so the latter. FAQs and forums are afterthoughts of the slothful, but now it's all we have.

I agree with ProfRob and I would add "better documentation".

As a note, when I pull on my pants, I sit on my bed, start my pants onto my feet, roll back and pull both legs up at once

light travels at about 30cm/nS. The Uno can capture +/- 1μS at best, so, at best, your accuracy will be +/- 30m.

In the nRF24 library I'm using, there timeouts, meaning that you will never know exactly how many μS a network.read() will take, adding multiples of 30m to the best case.

+/-2m is not possible using an Uno and any radio.

Try two GPS's, one on each module with each Nano and take the difference between the two. I'm pretty sure that would meet your spec. (Amazon) Yes, one GPS is rather inaccurate, but the inaccuracy is the same on two relatively close (google "differential GPS") That would be a cool project! And! you could log the track! You can find less expensive modules on AliExpress (caveat emptor and 20-90 days delivery)

One little project and you're hooked! You know you're going to want another sensor in the yard, so consider a gateway running MQTT (called a broker). Once you have that, it's really easy to add more sensors.

But if you're really strong willed an will only be using two devices ever, you might look at https://nrf24.github.io/RF24/index.html. You can get an Arduino Nano and an nRF24 radio for about $3.50 from Aliexpress (downside: delivery takes ~2 months, so get 10 each.)

MySensors Library can do this, too, but I find it a little bloated.

Personal note: I'm 70, retired engineer, and have only four projects going right now.

(yeah, this is really old in tech years, but I post in the event someone stumbles upon this.) I actually tried the GPS suggestion. I was wrong about the error between two identical GPS's. It's quite large. Check out the other suggestion first.

Oh, wait! I fell for it completely. I'm such a fool.

Your post is a marketing plug for seeeduino, not someone who just happened upon a few of these devices.

Not knowing what a Seeeduino Xiao is, I googled it and found the first entry past the ads a link to the product description. On that page I found "Compatible with Arduino IDE" along with a multitude of youtube videos.

Please pardon my sarcasm but I am compelled to suggest you start by searching "How to search with google"

I am using the TMRh20 libraries (not the MySensors library) and have the same problem. I'm pretty sure that there are interrupts that are not being reset. One of my other symptoms is that when I try to load or reload a program, the program doesn't start.

I have a program program that I run that works most of the time and gets me to the point of being able to reprogram the Arduino
//cli(); // disable all interrupts
WDTCSR = B00011000; // set watchdog timer into configuration mode
WDTCSR = 0; // turn off watchdog time interrupt.
//sei(); // allow interupts

I use this technique to load the program:

1. write program
2. use Tool-->port and set the port
3. on the device, press and hold reset button
4. <ctl>+u or click on upload icon
5. when compiling gas gauge is almost complete, release the reset button.

You may have to do 3)-5) several times. You could put:
Serial.begin(9600);
Serial.println("WDT reset");
at the end of the program to know that the device got reset.

I hope this helps you. I, too, would like something a little more controllable.

OSD

One little project and you're hooked! You know you're going to want another sensor in the yard, so consider a gateway running MQTT (called a broker). Once you have that, it's really easy to add more sensors.

But if you're really strong willed an will only be using two devices ever, you might look at https://nrf24.github.io/RF24/index.html. You can get an Arduino Nano and an nRF24 radio for about $3.50 from Aliexpress (downside: delivery takes ~2 months, so get 10 each.)

MySensors Library can do this, too, but I find it a little bloated.

Personal note: I'm 70, retired engineer, and have only four projects going right now.

I, too, am a "gray hair" (if I had hair). I despise cloud dependent devices. The reasons are many. ISPs, despite what they say, are not reliable. ISPs are so close to be monopolies, that they act like them. Your ISP can, and will, prevent access to the cloud if they have a competing product.

The manufacturers of cloud dependent devices, sell your information and statistics on how you use the devices. This is how they make money. When one of these manufacturers goes out of business, the company that buys up the IP continues to sell that information and ceases the little support that one did get.

I might be getting a little paranoid here, but I'm pretty sure there is unrelated-to-function software (spyware) incorporated into many products. (In the late 90's, the company for which I worked resisted the temptation to do so, despite heavy pressure from marketing.) I call it "ET phone home" Maybe the software is innocuous enough, but it can be hijacked by bad actors.

There is another problem plaguing home automation and that is poorly designed and poorly documented (which leads to pathetically supported) hardware and software. More so the latter. FAQs and forums are afterthoughts of the slothful, but now it's all we have.

I agree with ProfRob and I would add "better documentation".

As a note, when I pull on my pants, I sit on my bed, start my pants onto my feet, roll back and pull both legs up at once

@DenisJ Are you measuring a USB device? Look at something like this https://www.aliexpress.com/item/33019457512.html?gps-id=pcDetail404&scm=1007.16891.96945.0&scm_id=1007.16891.96945.0&scm-url=1007.16891.96945.0&pvid=824c24fa-034b-4801-b51d-50b2ad877945&_t=gps-id:pcDetail404,scm-url:1007.16891.96945.0,pvid:824c24fa-034b-4801-b51d-50b2ad877945,tpp_buckets:668%230%23131923%2330_668%230%23131923%2330_668%23888%233325%239_668%23888%233325%239_668%232846%238110%231995_668%232717%237561%23332__668%233374%2315176%2335_668%232846%238110%231995_668%232717%237561%23332_668%233164%239976%23761_668%233374%2315176%2335

(AliExpress: Cheap prices and one could question the quality, but for the most part they work. Shipping takes about a month. rarely faster)

@NeverDie You going to need an NTP Server. You can make one with an arduino nano, gps module and LAN module for under $20.

(yeah, this is really old in tech years, but I post in the event someone stumbles upon this.) I actually tried the GPS suggestion. I was wrong about the error between two identical GPS's. It's quite large. Check out the other suggestion first.

I have an Arduino Mesh network (see https://tmrh20.github.io/RF24Mesh/) (master and 4 nodes)
networkChannel 120, networkDataRate RF24_1MBPS, nodes 0-4

Now I want to have my master be an RPi because it can talk to the real world.

It looks like I have the RPi wired up and software loaded (per https://www.mysensors.org/build/raspberry). Now I need to know how to talk to my Arduino's.

Now how do I talk to my Arduino's?

o- general description of what you are trying to do
Raspberry Pi controller with serial gateway with nrf24l01+ to connect to Arduino's
o- the exact configure command you used
git clone https://github.com/mysensors/MySensors.git --branch master
cd MySensors
./configure --my-transport=rf24 --my-gateway=serial --my-serial-is-pty --my-serial-port=/dev/ttyMySensorsGateway
make
sudo ./bin/mysgw
[reboot RPi]
cd MySensors
sudo make install
sudo systemctl enable mysgw.service
sudo systemctl start mysgw.service
ls -als /dev/ttyMySensorsGateway [yeilds: 0 lrwxrwxrwx 1 root root 10 Apr 9 19:22 /dev/ttyMySensorsGateway -> /dev/pts/1]

o- the output from the test
Apr 09 18:47:32 INFO Config file /etc/mysensors.conf does not exist, creating new file.
Apr 09 18:47:32 INFO Starting gateway...
Apr 09 18:47:32 INFO Protocol version - 2.3.2
Apr 09 18:47:32 DEBUG Serial port /dev/ttyMySensorsGateway (115200 baud) created
Apr 09 18:47:32 INFO EEPROM file /etc/mysensors.eeprom does not exist, creating new file.
Apr 09 18:47:32 DEBUG MCO:BGN:INIT GW,CP=RNNGL---,FQ=NA,REL=255,VER=2.3.2
Apr 09 18:47:32 DEBUG TSF:LRT:OK
Apr 09 18:47:32 DEBUG TSM:INIT
Apr 09 18:47:32 DEBUG TSF:WUR:MS=0
Apr 09 18:47:32 DEBUG TSM:INIT:TSP OK
Apr 09 18:47:32 DEBUG TSM:INIT:GW MODE
Apr 09 18:47:32 DEBUG TSM:READY:ID=0,PAR=0,DIS=0
Apr 09 18:47:32 DEBUG MCO:REG:NOT NEEDED
Apr 09 18:47:32 DEBUG MCO:BGN:STP
Apr 09 18:47:32 DEBUG MCO:BGN:INIT OK,TSP=1
Apr 09 18:47:32 DEBUG TSM:READY:NWD REQ
Apr 09 18:47:32 DEBUG ?TSF:MSG:SEND,0-0-255-255,s=255,c=3,t=20,pt=0,l=0,sg=0,ft=0,st=OK:
[did not return to command prompt]
o- the settings you used in your controller
n/a

In the old days, yes, in the days before DHCP we had a similar problem on our cat 2 ethernet. I went over to the other guy and told him he was using my IP address. We went to the sysadmin and we agreed that he would use this range and I would use that. Done.

I suggest you talk to your neighbor. I suspect that they are clueless that they're messing with your network.

Consider this a lesson in design for robust networks and being neighborly.