Using RF24 with interrupts and replies

[ashw]

I am working on a recording barometer (and some other data). There will be a remote data collector and a display controller. Communication between the two is by RF24s.

The logic is this. The display controller sends a wake up signal to the data collector who replies with the current readings. To save power the display controller uses LowPower and SLEEP_FOREVER. The RF24 uses its interrupt to wake up the data collector, who then replies with the data.

This works with a weird anomaly: the reply is always 1 step behind the wake up.

The display sends: "wakeup n".
The collector replies with: "temp,dewpoint,barometer,solarpower,batterystate,wakeup n"
The display says that it received: "temp,dewpoint,barometer,solarpower,batterystate,wakeup n-1"

below is the code I am using.

Can anyone see what I am doing wrong?

```cpp
#include <Wire.h>

#include "LowPower.h"

#include <Adafruit_INA219.h>
#include <math.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,20,4);

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(9, 10); // CE, CSN

Adafruit_INA219 ina219(0x040);

Adafruit_BME280 bme;

const byte address[][6] = {"00001", "00002"};
int count = 0;

void setup() {
  Serial.begin(57600);
  // put your setup code here, to run once:
  lcd.begin(20,4);
  lcd.init();
  lcd.backlight();
  lcd.home();
  lcd.clear();

  analogReference(INTERNAL);
  bme.begin(0x76);
  
  ina219.begin();  //
  ina219.setCalibration_16V_400mA();
  
  pinMode(2, INPUT);
  radio.begin();
  radio.setChannel(72); 
  radio.openReadingPipe(0, address[0]);
  radio.openWritingPipe(address[1]);
  radio.setPALevel(RF24_PA_MIN);
  radio.maskIRQ(1,1,0);    //mask all IRQ triggers except for receive (1 is mask, 0 is no mask)
  radio.startListening();
 
}

void loop() {
  // put your main code here, to run repeatedly:
  char text[32] = "";
  String reply;

   radio.startListening();
   lcd.noBacklight();
   attachInterrupt(0, interruptFunction, FALLING);
   LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
   detachInterrupt(0);
   lcd.backlight();
   
//   while(radio.available() & c < 8) 
    if(radio.available() ){
      lcd.clear();
      radio.read(&text, sizeof(text));
      lcd.print(text);
      reply = getData() + "#" + text;
      lcd.setCursor(0,1);
      lcd.print(reply);
      reply.toCharArray(text, reply.length()+5);
      radio.stopListening();
      radio.write(&text, 32 );
   }
   else lcd.print("*");
   count++;if(count == 80) {count = 0;lcd.clear();lcd.setCursor(0,0);}
   delay(2000);


}

void interruptFunction() {}

String getData(){
  float tempC, rh, dewpointC, t, pressure;
  int tempF, dewpointF, power, count;
  String readings = "";
  bool report;

  tempC = bme.readTemperature();
  tempF = int(32 + 1.8 * tempC);
  
  rh = bme.readHumidity();
  t = logf(rh/100) + ((17.625 * tempC) / (243.04 + tempC) );
  dewpointC = (243.04 * t) / 
              (17.625 - t); 
  dewpointF = int(32 + 1.8 * dewpointC);
  
  pressure = 1.07+(0.02953*bme.readPressure()) / 100.0F;
  
  power = int(ina219.getPower_mW());
  power = 150;
  readings = String(tempF) + "," 
           + String(dewpointF) + ","
           + String(pressure) + ","
           + String(power) + ","
           + 5123 ;//int(1 11.5 * analogRead(A0)  ); //battery state

//  readings.toCharArray(payload, 32);
  return readings;
}

`

#include <Wire.h>

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,20,4);

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(9, 10); // CE, CSN

const byte address[][6] = {"00001", "00002"};
int count = 0;

void setup() {

Serial.begin(57600);

  lcd.begin(20,4);
  lcd.init();
  lcd.backlight();
  lcd.home();
  lcd.clear();

  radio.begin();
  radio.setChannel(72); 
  radio.openWritingPipe(address[0]);
  radio.openReadingPipe(0, address[1]);
  radio.setPALevel(RF24_PA_MIN, true);
  radio.stopListening();
}
 


void loop() {

  char text[32]; 
  String txt = "wakeup ";

  lcd.clear();
  txt = txt + String(count);
  txt.toCharArray(text, txt.length()+5);
  lcd.setCursor(0,0);
  lcd.print("sending ");lcd.print(count);
  radio.stopListening();
  radio.write(&text, 32);
  radio.startListening();
  
  delay(5);
  if(radio.available()){
    lcd.setCursor(0,1);
    radio.read(&text, 32);
    lcd.print(text);
    Serial.println(text);
   }
    count++;
  delay(5000);

}

[ashw]

Solved. I wasn't waiting long enough for the reply. I inserted the following before getting the data.

while( !radio.available() & c < 10){
delay(10);
c++;
}

[gilshultz]

@ashw

Solved

Sometimes just turning the other way for a short while and the solution comes. Good Job and thanks for letting us know.