BATTERY MONITORING ARDUINO RX(2 WAY)

/* PROGRAM BY: RANDY N. CAÑADA,DEC 2025
Arduino Uno wiring
MOSI -> D11
MISO -> D12
SCK  -> D13
CSN  -> D10
CE   -> D9

Arduino Uno (Receiver + INA219 Feedback Transmitter)
*/

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <Wire.h>
#include <Adafruit_INA219.h>

RF24 radio(9, 10); // CE, CSN
const byte address[][6] = {"00001", "00002"}; // ESP32->Arduino, Arduino->ESP32

Adafruit_INA219 ina219;
char receivedText[32];
int LED = 7;

void setup() {
  Serial.begin(9600);
  pinMode(LED, OUTPUT);

  radio.begin();
  radio.setPALevel(RF24_PA_MIN);

  radio.openReadingPipe(1, address[0]); // Listen for ESP32 commands
  radio.openWritingPipe(address[1]);    // Send feedback to ESP32

  radio.startListening();

  if (!ina219.begin()) {
    Serial.println("Failed to find INA219 chip");
    while (1);
  }
  ina219.setCalibration_32V_2A();
  Serial.println("INA219 ready!");
}

void loop() {
  if (radio.available()) {
    radio.read(&receivedText, sizeof(receivedText));
    Serial.print("Received: ");
    Serial.println(receivedText);

    if (strcmp(receivedText, "LED ON") == 0) digitalWrite(LED, HIGH);
    else if (strcmp(receivedText, "LED OFF") == 0) digitalWrite(LED, LOW);

    // --- Measure battery ---
    float busVoltage = ina219.getBusVoltage_V();
    float current_mA = ina219.getCurrent_mA();

    char vStr[10], iStr[10], feedback[32];
    dtostrf(busVoltage, 4, 2, vStr);
    dtostrf(current_mA, 6, 1, iStr);
    snprintf(feedback, sizeof(feedback), "V=%sV I=%smA", vStr, iStr);

    // --- Send feedback ---
    radio.stopListening();   // Switch to TX
    delay(50);               // Give ESP32 time to enter RX mode
    bool ok = radio.write(&feedback, sizeof(feedback));
    if (ok) {
      Serial.print("Sent feedback: ");
      Serial.println(feedback);
    } else {
      Serial.println("Feedback send failed.");
    }
    radio.startListening();  // Back to RX
  }
}