I started out with NRF 2.4 MHz radios for my 8 nodes MySensors and Domoticz. As I also install WiFi networks for customers and have access to our equipment at work I did a measurement at home because I could not get a reliable network.
First measurement revealed that my DECT wireless phone occupied the same channel that was the default for the NRF radios. And that my neighbors run their WiFi occupying all other channels. Equipment used was Ekahau.
I tried to tweak the channels but no avail.
So, I bought new radios, RFM833, and that was the end of my troubles. For two year now my eight nodes have not skipped a beat. I measure temperature, humidity, light (lux), UV and radioactivity.

And all my WiFi at home is at 5GHz as the 2.4 was exhausted.
I have about 40 NRF radios in a box with no use for them.

The code that you posted:
send(msg.set(value==HIGH ? 1 : 0))
Translates to this
If ”value” is HIGH (true) then send 1, if not send 0

It has nothing to do with PIN 0 or 1

The same goes for
digitalWrite(RELAY_PIN_1, loadState(CHILD_ID_RELAY1)?RELAY_ON:RELAY_OFF);
It translates to
On RELAY_PIN_1, if it’s state is 1 write HIGH to RELAY_PIN_1 else write LOW.

If you use serial in your sketch you can’t use PIN 0 or 1 as those pins are TX and RX.

Be aware that most of the cheap NRF boards from China are counterfeit. If you have those in an environment with a lot of WiFi you won’t get any range at all. And all “modifications” to improve range posted on YouTube are not any improvement.
You need to buy real NRF modules with external antenna.
Just my two cents.

@rodaman if you have bought real NRF modules you have been satisfied.
Or if you have bought RFM 433, 833 or 915 MHz radios you had been more that pleased.
Not MySensors fault.

I do, really easy to setup. I have decided to only show the temperatures and battery status when battery level is low.

// Debug
#define MY_DEBUG
// Enable and select radio type attached
#define   MY_RADIO_RFM69
#define   MY_IS_RFM69HW
#define   MY_RFM69_NEW_DRIVER
#define   MY_RFM69_FREQUENCY RFM69_868MHZ
// #define   MY_RFM69_ENABLE_ENCRYPTION

#include <MySensors.h>

#define SKETCH_NAME    "Test-text"
#define SKETCH_VERSION "1.0"

#define CHILD_ID_RSSI_INFO  1

// Mysensors settings
MyMessage msgRSSI(CHILD_ID_RSSI_INFO, V_TEXT);

void before()
{
}

void setup()
{
  Serial.begin(115200); // for serial debugging.
  Serial.println(F("Start up sensor."));
}

void presentation()
{
  present(CHILD_ID_RSSI_INFO, S_INFO, "RSSI Info");
}

void loop()
{
#ifdef MY_DEBUG
  Serial.println(F("Starting new measurements"));
#endif
  CheckRSSI();
  // Sleep 
#ifdef MY_DEBUG
  Serial.println(F("Waiting 1 minute"));
#endif
  wait(60000);
}

Change

lecture_adc = BAR_SENSOR_ANALOG_PIN;

To

lecture_adc = analogRead(BAR_SENSOR_ANALOG_PIN);

I am using this:

// Bosch BME280 Embedded Adventures MOD-1022 weather multi-sensor Arduino code, 
// written originally by Embedded Adventures. 
// https://github.com/embeddedadventures/BME280
#include <BME280_MOD-1022.h>```

THANKS!!
That did it:

RSSI String: T: 127 R:-49 PL:-2 PP:0
TSF:MSG:SEND,13-13-0-0,s=1,c=1,t=47,pt=0,l=23,sg=0,ft=0,st=OK:T: 127 R:-49 PL:-2 PP:0

Yes, and I am very pleased with it.

I started with MySensors, Pro Mini and NRF24. I had tons of problems. I borrowed from work our WiFi scanner equipment and checked the 2.4 GHz. It was a total mess. Our DECT-phone almost killed the channel that was used for MySensors. And I discovered, as many has, the NRF24 was all counterfeit.
So, i trashed all NRF24 and moved to RFM69. That was nearly three years ago. My gateway is a Raspberry Pi.
My controller is Domoticz.
Conclusion, and a note to all MySensors users out there. Move away from NRF24 and go with RFM69, you will never look back.

The code that you posted:
send(msg.set(value==HIGH ? 1 : 0))
Translates to this
If ”value” is HIGH (true) then send 1, if not send 0

It has nothing to do with PIN 0 or 1

The same goes for
digitalWrite(RELAY_PIN_1, loadState(CHILD_ID_RELAY1)?RELAY_ON:RELAY_OFF);
It translates to
On RELAY_PIN_1, if it’s state is 1 write HIGH to RELAY_PIN_1 else write LOW.

If you use serial in your sketch you can’t use PIN 0 or 1 as those pins are TX and RX.

I started out with NRF 2.4 MHz radios for my 8 nodes MySensors and Domoticz. As I also install WiFi networks for customers and have access to our equipment at work I did a measurement at home because I could not get a reliable network.
First measurement revealed that my DECT wireless phone occupied the same channel that was the default for the NRF radios. And that my neighbors run their WiFi occupying all other channels. Equipment used was Ekahau.
I tried to tweak the channels but no avail.
So, I bought new radios, RFM833, and that was the end of my troubles. For two year now my eight nodes have not skipped a beat. I measure temperature, humidity, light (lux), UV and radioactivity.

And all my WiFi at home is at 5GHz as the 2.4 was exhausted.
I have about 40 NRF radios in a box with no use for them.

@rodaman if you have bought real NRF modules you have been satisfied.
Or if you have bought RFM 433, 833 or 915 MHz radios you had been more that pleased.
Not MySensors fault.

Be aware that most of the cheap NRF boards from China are counterfeit. If you have those in an environment with a lot of WiFi you won’t get any range at all. And all “modifications” to improve range posted on YouTube are not any improvement.
You need to buy real NRF modules with external antenna.
Just my two cents.

I do, really easy to setup. I have decided to only show the temperatures and battery status when battery level is low.

@sundberg84 if you look at the schematic you have connected MySX pin 10 to D2, but according to the spec for the MySX 2.4 it should go to D4.

I have now checked the PCB, and you are right @JPM
Pin 6 of the flash chip is not connected at all. No wonder I could not get that to work. Strangely is that the schematic is OK.
Thanks for finding this, I will modify my boards to get them working.

I checked the schematic, and:
First mistake: Seems that the schematic is OK, the label for SCK (pin 6) is connected to physical pin 16 which is PCINT13 on the Arduino,
Second mistake: that is a bug, filter capacitor is not connected correctly.
Third mistake: That is also a bug, pin 7 and 3 should be connected to VCC
Now I am going to check the PCB, be back shortly,

I just checked my batch of Rev 10, random check of the batch checked out OK. I have 20 boards.