weatherstation-datacollector/main.cpp

#include <Arduino.h>
#include <SPI.h>
#include <Wire.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <Adafruit_BME280.h>
#include <avr/wdt.h>
#include <avr/sleep.h>
#include <avr/power.h>
#include <EEPROM.h>
#include <avr/io.h>

// Capture and persist reset cause as early as possible
// Store MCUSR in a noinit section so C runtime doesn't clear it
static uint8_t mcusr_mirror __attribute__((section(".noinit")));

void wdt_init(void) __attribute__((naked)) __attribute__((section(".init3")));
void wdt_init(void) {
  mcusr_mirror = MCUSR;
  MCUSR = 0;
  wdt_disable();
  __asm__ __volatile__ ("ret");
}

static uint8_t lastResetFlagsGlobal = 0;

// Battery Optimization Settings
#define ENABLE_CHANGE_DETECTION 1  // Only transmit when values change
#define TEMP_CHANGE_THRESHOLD 0.1  // °C - transmit if temp changes by this amount (reduced from 0.2 for better noise filtering)
#define HUM_CHANGE_THRESHOLD 2.0   // % - transmit if humidity changes by this amount  
#define PRES_CHANGE_THRESHOLD 1.0  // hPa - transmit if pressure changes by this amount
#define ALIVE_INTERVAL 10          // Force transmission every N cycles even if no change (10*30s = 5min)
#define SENSOR_INTERVAL 30         // Read sensors every N seconds (30s = good balance)

// CC1101 Register addresses
#define CC1101_IOCFG0       0x02
#define CC1101_PKTLEN       0x06
#define CC1101_PKTCTRL1     0x07
#define CC1101_SYNC1        0x04
#define CC1101_SYNC0        0x05
#define CC1101_PKTCTRL0     0x08
#define CC1101_CHANNR       0x0A
#define CC1101_FSCTRL1      0x0B
#define CC1101_FREQ2        0x0D
#define CC1101_FREQ1        0x0E
#define CC1101_FREQ0        0x0F
#define CC1101_MDMCFG4      0x10
#define CC1101_MDMCFG3      0x11
#define CC1101_MDMCFG2      0x12
#define CC1101_MDMCFG1      0x13
#define CC1101_MDMCFG0      0x14
#define CC1101_DEVIATN      0x15
#define CC1101_MCSM1        0x17
#define CC1101_MCSM0        0x18
#define CC1101_FOCCFG       0x19
#define CC1101_BSCFG        0x1A
#define CC1101_AGCCTRL2     0x1B
#define CC1101_AGCCTRL1     0x1C
#define CC1101_AGCCTRL0     0x1D
#define CC1101_FREND1       0x21
#define CC1101_FREND0       0x22
#define CC1101_FSCAL3       0x23
#define CC1101_FSCAL2       0x24
#define CC1101_FSCAL1       0x25
#define CC1101_FSCAL0       0x26
#define CC1101_TEST2        0x2C
#define CC1101_TEST1        0x2D
#define CC1101_TEST0        0x2E
#define CC1101_PATABLE      0x3E
#define CC1101_TXFIFO       0x3F

// Command strobes
#define CC1101_SRES         0x30
#define CC1101_SCAL         0x33
#define CC1101_STX          0x35
#define CC1101_SIDLE        0x36
#define CC1101_SFTX         0x3B

// Status registers
#define CC1101_PARTNUM      0x30
#define CC1101_VERSION      0x31
#define CC1101_RSSI         0x34
#define CC1101_MARCSTATE    0x35

// Pin definitions
#define CC1101_CS   10
#define LED_PIN     4
#define ONE_WIRE_BUS 3
#define PRES_OFFSET 41.0F

#define MYNODEID    1

// Change detection variables
float lastTxDsTempC = -999.0;
float lastTxBmeTempC = -999.0;
float lastTxBmeHum = -999.0;
float lastTxBmePres = -999.0;
uint8_t cyclesSinceLastTx = 0;

// Sensor interval tracking
uint16_t wakeCount = 0;
volatile uint8_t watchdog_wakeups = 0;  // Counter for watchdog interrupts

// Watchdog ISR - wakes MCU from sleep
ISR(WDT_vect) {
  watchdog_wakeups++;
  // Note: do NOT disable watchdog here - it will be re-enabled before next sleep
}

void sleep_1s(void) {
  // Ensure serial is flushed before sleep
  Serial.flush();
  
  // Disable UART to save power during sleep (~2-3mA)
  power_usart0_disable();
  
  // Configure watchdog for 1-second interrupt-based wake
  cli();  // Disable interrupts during setup
  wdt_reset();
  WDTCSR |= (1 << WDCE) | (1 << WDE);  // Enable watchdog configuration change
  WDTCSR = (1 << WDIE) | (1 << WDP2) | (1 << WDP1);  // 1-second, interrupt only
  sei();  // Re-enable interrupts
  
  // Set sleep mode to Power Down (lowest power: ~5-10µA)
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable();
  
  // Enter power-down sleep - wakes on watchdog interrupt
  sleep_cpu();
  
  // Execution resumes here after watchdog interrupt
  sleep_disable();
  wdt_disable();  // Stop watchdog after waking
  
  // Re-enable UART after sleep
  power_usart0_enable();
  
  // Small delay to let UART stabilize
  delayMicroseconds(100);
}

// Payload structure
struct Payload {
  uint8_t  magic1;
  uint8_t  magic2;
  uint8_t  version;
  uint8_t  nodeId;
  uint16_t seq;
  int16_t  t_ds10;
  int16_t  t_bme10;
  uint16_t hum10;
  uint16_t pres1;
  uint16_t vcc;     // VCC in millivolts
  uint8_t  crc;
};

// Ensure payload size matches radio PKTLEN expectations (17 bytes)
static_assert(sizeof(Payload) == 17, "Payload size must be 17 bytes");

Payload p;
static uint16_t seq = 0;

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature ds18(&oneWire);
Adafruit_BME280 bme;
static bool bme_ok = false;

struct BmeSample {
  float tempC;
  float hum;
  float presHpa;
};

uint8_t calcCrc(const uint8_t *data, uint8_t len) {
  uint8_t c = 0;
  for (uint8_t i = 0; i < len; i++) c ^= data[i];
  return c;
}

// Read VCC voltage in millivolts using internal 1.1V reference
uint16_t readVcc() {
  // Set ADC reference to internal 1.1V and measure VCC
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Start conversion
  while (bit_is_set(ADCSRA, ADSC)); // Wait for completion
  uint16_t result = ADC;
  // Calculate VCC in millivolts: internal_ref * 1024 / ADC reading
  // Calibrated: 1450512 gives 3300mV on this chip (internal ref ~1.42V)
  uint16_t vcc = (1450512L / result);
  
  // Disable ADC to save power (~200µA)
  power_adc_disable();
  
  return vcc;
}

// Check if sensor values have changed enough to warrant transmission
// NOTE: This function ONLY checks for change. Alive/heartbeat logic is handled in loop().
bool valuesChanged(float dsTempC, float bmeTempC, float bmeHum, float bmePres) {
  // Note: Pressure changes do NOT trigger a transmission. Pressure is sent only
  // when temperature/humidity trigger or during alive/heartbeat transmissions.
  #if ENABLE_CHANGE_DETECTION
  if (abs(dsTempC - lastTxDsTempC) >= TEMP_CHANGE_THRESHOLD) return true;
  if (abs(bmeTempC - lastTxBmeTempC) >= TEMP_CHANGE_THRESHOLD) return true;
  if (abs(bmeHum - lastTxBmeHum) >= HUM_CHANGE_THRESHOLD) return true;
  return false;  // No significant changes in temp/humidity
  #else
  return true;  // Always transmit if change detection disabled
  #endif
}

// CC1101 SPI functions
void cc1101_WriteReg(uint8_t addr, uint8_t value) {
  digitalWrite(CC1101_CS, LOW);
  delayMicroseconds(10);
  SPI.transfer(addr);
  SPI.transfer(value);
  delayMicroseconds(10);
  digitalWrite(CC1101_CS, HIGH);
}

uint8_t cc1101_ReadReg(uint8_t addr) {
  digitalWrite(CC1101_CS, LOW);
  delayMicroseconds(10);
  SPI.transfer(addr | 0x80); // Read bit
  uint8_t val = SPI.transfer(0);
  delayMicroseconds(10);
  digitalWrite(CC1101_CS, HIGH);
  return val;
}

void cc1101_WriteStrobe(uint8_t strobe) {
  digitalWrite(CC1101_CS, LOW);
  delayMicroseconds(10);
  SPI.transfer(strobe);
  delayMicroseconds(10);
  digitalWrite(CC1101_CS, HIGH);
}

uint8_t cc1101_ReadStatus(uint8_t addr) {
  digitalWrite(CC1101_CS, LOW);
  delayMicroseconds(10);
  SPI.transfer(addr | 0xC0); // Burst read bit
  uint8_t val = SPI.transfer(0);
  delayMicroseconds(10);
  digitalWrite(CC1101_CS, HIGH);
  return val;
}

void cc1101_SetPower(uint8_t paValue) {
  digitalWrite(CC1101_CS, LOW);
  delayMicroseconds(10);
  SPI.transfer(CC1101_PATABLE | 0x40); // Burst write to PATABLE
  for (uint8_t i = 0; i < 8; i++) {
    SPI.transfer(paValue);
  }
  delayMicroseconds(10);
  digitalWrite(CC1101_CS, HIGH);
}

// Select TX power based on battery voltage to prevent brown-out
uint8_t getAdaptiveTxPower(uint16_t vccMv) {
  if (vccMv >= 3000) return 0xC0;      // Full power at 3.0V+
  else if (vccMv >= 2800) return 0x60; // Medium power at 2.8-3.0V (lowered from 0x84)
  else return 0x40;                    // Low power below 2.8V
}

void cc1101_WriteTxFifo(uint8_t *data, uint8_t len) {
  digitalWrite(CC1101_CS, LOW);
  delayMicroseconds(10);
  SPI.transfer(CC1101_TXFIFO | 0x40); // Burst write
  for (uint8_t i = 0; i < len; i++) {
    SPI.transfer(data[i]);
  }
  delayMicroseconds(10);
  digitalWrite(CC1101_CS, HIGH);
}

BmeSample readBmeOnce() {
  if (!bme_ok) {
    BmeSample s{};
    s.tempC = NAN; s.hum = NAN; s.presHpa = NAN;
    return s;
  }
  BmeSample s{};

  // Force a single reading
  bme.setSampling(Adafruit_BME280::MODE_FORCED,
                  Adafruit_BME280::SAMPLING_X2,
                  Adafruit_BME280::SAMPLING_X16,
                  Adafruit_BME280::SAMPLING_X1);
  delay(10);

  s.tempC = bme.readTemperature();
  s.hum   = bme.readHumidity();
  s.presHpa = (bme.readPressure() / 100.0F) + PRES_OFFSET;

  // Return to sleep to save power
  bme.setSampling(Adafruit_BME280::MODE_SLEEP,
                  Adafruit_BME280::SAMPLING_X2,
                  Adafruit_BME280::SAMPLING_X16,
                  Adafruit_BME280::SAMPLING_X1);

  return s;
}

// Attempt to recover a stuck I2C bus by toggling SCL until SDA is released
static void i2cBusRecover() {
  pinMode(A4, INPUT_PULLUP); // SDA
  pinMode(A5, INPUT_PULLUP); // SCL
  delay(5);
  if (digitalRead(A4) == LOW) {
    pinMode(A5, OUTPUT);
    for (uint8_t i = 0; i < 9 && digitalRead(A4) == LOW; i++) {
      digitalWrite(A5, LOW);
      delayMicroseconds(5);
      digitalWrite(A5, HIGH);
      delayMicroseconds(5);
    }
  }
}

float readDs18Median(uint8_t samples = 3) {
  float buf[5];  // up to 5 samples
  samples = (samples > 5) ? 5 : samples;
  for (uint8_t i = 0; i < samples; i++) {
    wdt_reset();  // Feed watchdog during slow sensor reads
    ds18.requestTemperatures();
    ds18.setWaitForConversion(true);  // block until done
    buf[i] = ds18.getTempCByIndex(0);
  }
  // simple insertion sort for small N
  for (uint8_t i = 1; i < samples; i++) {
    float v = buf[i];
    uint8_t j = i;
    while (j > 0 && buf[j - 1] > v) { buf[j] = buf[j - 1]; j--; }
    buf[j] = v;
  }
  return buf[samples / 2];
}

float smoothEma(float raw, float alpha = 0.2f) {
  static float ema = NAN;
  if (isnan(ema)) ema = raw;
  else ema = alpha * raw + (1.0f - alpha) * ema;
  return ema;
}

bool waitForIdle(uint16_t timeoutMs) {
  unsigned long start = millis();
  while (millis() - start < timeoutMs) {
    if ((cc1101_ReadStatus(CC1101_MARCSTATE) & 0x1F) == 0x01) return true; // 0x01 = IDLE
    delay(1);
  }
  return false;
}

void cc1101_InitFSK() {
  Serial.println("Initializing CC1101 in GFSK mode (1.2 kBaud, 5 kHz dev, 58 kHz BW)...");
  
  // Reset CC1101
  cc1101_WriteStrobe(CC1101_SRES);
  delay(10);
  
  // Configure for GFSK modulation at 868.3 MHz, 1.2 kBaud, 5 kHz deviation
  cc1101_WriteReg(CC1101_IOCFG0, 0x06);
  cc1101_WriteReg(CC1101_PKTCTRL0, 0x00);
  cc1101_WriteReg(CC1101_PKTCTRL1, 0x00);
  cc1101_WriteReg(CC1101_PKTLEN, sizeof(Payload));
  // Debug check: confirm PKTLEN register matches struct size
  uint8_t pktlenReg = cc1101_ReadReg(CC1101_PKTLEN);
  Serial.print("PKTLEN(struct/reg): ");
  Serial.print(sizeof(Payload));
  Serial.print("/");
  Serial.println(pktlenReg);
  cc1101_WriteReg(CC1101_SYNC1, 0xD3);
  cc1101_WriteReg(CC1101_SYNC0, 0x91);
  cc1101_WriteReg(CC1101_CHANNR, 0x00);
  cc1101_WriteReg(CC1101_FSCTRL1, 0x06);
  
  // Set frequency to 868.3 MHz
  cc1101_WriteReg(CC1101_FREQ2, 0x21);
  cc1101_WriteReg(CC1101_FREQ1, 0x65);
  cc1101_WriteReg(CC1101_FREQ0, 0x6A);
  
  // Modem configuration
  cc1101_WriteReg(CC1101_MDMCFG4, 0xF8);
  cc1101_WriteReg(CC1101_MDMCFG3, 0x83);
  cc1101_WriteReg(CC1101_MDMCFG2, 0x12);
  cc1101_WriteReg(CC1101_MDMCFG1, 0x22);
  cc1101_WriteReg(CC1101_MDMCFG0, 0xF8);
  cc1101_WriteReg(CC1101_DEVIATN, 0x15);
  cc1101_WriteReg(CC1101_MCSM0, 0x18);
  cc1101_WriteReg(CC1101_FOCCFG, 0x1D);
  cc1101_WriteReg(CC1101_BSCFG, 0x1C);
  cc1101_WriteReg(CC1101_MCSM1, 0x30);
  
  // AGC control
  cc1101_WriteReg(CC1101_AGCCTRL2, 0xC7);
  cc1101_WriteReg(CC1101_AGCCTRL1, 0x00);
  cc1101_WriteReg(CC1101_AGCCTRL0, 0xB0);

  // Front-end configuration
  cc1101_WriteReg(CC1101_FREND1, 0xB6);
  cc1101_WriteReg(CC1101_FREND0, 0x17);
  cc1101_WriteReg(CC1101_FSCAL3, 0xEA);
  cc1101_WriteReg(CC1101_FSCAL2, 0x2A);
  cc1101_WriteReg(CC1101_FSCAL1, 0x00);
  cc1101_WriteReg(CC1101_FSCAL0, 0x1F);
  
  cc1101_WriteReg(CC1101_TEST2, 0x88);
  cc1101_WriteReg(CC1101_TEST1, 0x31);
  cc1101_WriteReg(CC1101_TEST0, 0x09);
  
  // Set PA table for maximum TX power (~10dBm)
  cc1101_SetPower(0xC0);

  // Calibrate frequency synthesizer
  cc1101_WriteStrobe(CC1101_SIDLE);
  delay(1);
  cc1101_WriteStrobe(CC1101_SCAL);
  delay(3);
  for (uint16_t i = 0; i < 500; i++) {
    uint8_t st = cc1101_ReadStatus(CC1101_MARCSTATE) & 0x1F;
    if (st != 0x13 && st != 0x14) break;
    delay(1);
  }
  
  Serial.println("CC1101 initialization complete");
}

void setup() {
  // Disable watchdog immediately
  wdt_reset();
  wdt_disable();
  wdt_reset();
  
  // Power optimization - disable unused peripherals
  power_twi_disable();  // Will re-enable for I2C
  power_spi_disable();  // Will re-enable for SPI
  ACSR |= (1 << ACD);   // Disable analog comparator (~25µA saved)
  
  // Set up LED pin FIRST
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, HIGH);
  
  wdt_reset();
  
  // Initialize serial WITHOUT any delay
  Serial.begin(9600);
  // NO DELAY - immediate operation
  
  wdt_reset();
  
  Serial.println("\n========== BOOT ==========");
  wdt_reset();
  Serial.flush();
  wdt_reset();

  // Re-enable I2C and SPI for sensor initialization
  power_twi_enable();
  power_spi_enable();

  // Report and persist the last reset cause
  uint8_t lastResetFlags = mcusr_mirror;
  lastResetFlagsGlobal = lastResetFlags;
  EEPROM.update(0, lastResetFlags);
  Serial.print("Reset flags: 0x");
  Serial.print(lastResetFlags, HEX);
  Serial.print(" (");
  if (lastResetFlags & (1<<WDRF)) Serial.print("WDT ");
  if (lastResetFlags & (1<<BORF)) Serial.print("BOR ");
  if (lastResetFlags & (1<<EXTRF)) Serial.print("EXT ");
  if (lastResetFlags & (1<<PORF)) Serial.print("POR ");
  Serial.println(")");
  Serial.flush();
  
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
 
  // Initialize SPI
  Serial.println("Init SPI...");
  Serial.flush();
  SPI.begin();
  pinMode(CC1101_CS, OUTPUT);
  digitalWrite(CC1101_CS, HIGH);
  Serial.println("SPI OK");
  Serial.flush();

  // Initialize I2C with bus recovery to avoid hangs
  Serial.println("Init I2C...");
  Serial.flush();
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
  
  i2cBusRecover();
  Wire.begin();
  Serial.println("I2C OK");
  Serial.flush();
  
  // Initialize BME280
  Serial.print("Init BME280...");
  Serial.flush();
  bme_ok = bme.begin(0x76);
  if (!bme_ok) bme_ok = bme.begin(0x77);
  Serial.println(bme_ok ? "OK" : "FAIL");
  Serial.flush();
  
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
  
  // Initialize CC1101
  Serial.println("Init CC1101...");
  Serial.flush();
  cc1101_InitFSK();
  Serial.println("CC1101 OK");
  Serial.flush();
  
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
  
  Serial.println("About to init DS18B20...");
  Serial.flush();
  wdt_reset();
  
  // Initialize DS18B20 - now with watchdog protection
  ds18.begin();
  wdt_reset();
  ds18.setResolution(12);
  wdt_reset();
  
  Serial.print("Found ");
  Serial.print(ds18.getDeviceCount());
  Serial.println(" DS18B20 device(s)");
  Serial.flush();
  wdt_reset();
  
  // All initialized
  Serial.println("========== SETUP COMPLETE ==========");
  Serial.flush();
  
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
  delay(100);
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
  
  Serial.println("Ready to transmit");
}

void loop() {
  wakeCount++;
  
  // Only read sensors every SENSOR_INTERVAL seconds
  if (wakeCount % SENSOR_INTERVAL != 0) {
    Serial.print(".");  // Heartbeat indicator
    Serial.flush();
    sleep_1s();  // Sleep for 1 second
    return;
  }
  
  wdt_reset();
  Serial.println("");  // Newline after dots
  Serial.print("[Cycle ");
  Serial.print(wakeCount);
  Serial.println("] Reading sensors...");
  wdt_reset();
  
  // Re-enable ADC for VCC reading (will be disabled after read)
  power_adc_enable();
  
  // Read DS18B20 temperature with median + EMA filtering
  float dsRaw = readDs18Median(3);  // ~2.25s total for 3 samples at 12-bit
  wdt_reset();
  float dsTempC = smoothEma(dsRaw, 0.2f);
  wdt_reset();
  
  // Read BME280
  BmeSample bmeSample = readBmeOnce();
  wdt_reset();
  
  // Read VCC voltage
  uint16_t vccMv = readVcc();
  wdt_reset();
  
  // Fill payload
  p.magic1 = 0x42;
  p.magic2 = 0x99;
  // Bump payload format to version 2 (includes VCC field)
  p.version = (uint8_t)(2 | ((lastResetFlagsGlobal & 0x0F) << 4));
  p.nodeId = MYNODEID;
  p.seq = seq++;
  p.t_ds10 = (int16_t)(dsTempC * 10.0);
  p.t_bme10 = (int16_t)(bmeSample.tempC * 10.0);
  p.hum10 = (uint16_t)(bmeSample.hum * 10.0);
  p.pres1 = (uint16_t)(bmeSample.presHpa * 10.0);
  p.vcc = vccMv;
  
  p.crc = 0;
  p.crc = calcCrc((uint8_t*)&p, sizeof(Payload) - 1);
  
  wdt_reset();
  
  // Check if transmission is needed
  cyclesSinceLastTx++;
  bool changed = valuesChanged(dsTempC, bmeSample.tempC, bmeSample.hum, bmeSample.presHpa);
  bool alive = (lastTxDsTempC != -999.0 && cyclesSinceLastTx >= ALIVE_INTERVAL) || (lastTxDsTempC == -999.0);
  bool shouldTransmit = changed || alive;
  
  wdt_reset();
  
  if (!shouldTransmit) {
    Serial.print("No change (cycle ");
    Serial.print(cyclesSinceLastTx);
    Serial.println("), skipping TX");
    wdt_reset();
    
    // Flash LED briefly to show we're alive but not transmitting
    digitalWrite(LED_PIN, HIGH);
    delay(50);
    digitalWrite(LED_PIN, LOW);
    wdt_reset();
    
    // Sleep for remaining time of this cycle
    Serial.flush();
    sleep_1s();
    return;  // Skip transmission
  }
  
  // Values changed or alive signal - proceed with transmission
  if (changed) {
    Serial.print("Values changed, transmitting seq=");
  } else {
    Serial.print("ALIVE signal, transmitting seq=");
  }
  wdt_reset();
  Serial.println(seq);
  wdt_reset();
  
  // Update last transmitted values
  lastTxDsTempC = dsTempC;
  lastTxBmeTempC = bmeSample.tempC;
  lastTxBmeHum = bmeSample.hum;
  lastTxBmePres = bmeSample.presHpa;
  cyclesSinceLastTx = 0;
  
  wdt_reset();
  
  // Set fixed TX power to 0xC0 (~10 dBm - maximum)
  cc1101_SetPower(0xC0);
  
  // Transmit
  cc1101_WriteStrobe(CC1101_SIDLE);
  delay(5);
  wdt_reset();
  
  // Flush TX FIFO
  cc1101_WriteStrobe(CC1101_SFTX);
  delay(2);
  
  // Write data to TX FIFO
  cc1101_WriteTxFifo((uint8_t*)&p, sizeof(Payload));
  wdt_reset();
  
  // Start transmission
  cc1101_WriteStrobe(CC1101_STX);

  // Wait until radio returns to IDLE or timeout
  bool txDone = waitForIdle(150);
  wdt_reset();
  if (!txDone) {
    Serial.print("[tx-timeout]");
  } else {
    Serial.print(".");
  }
  wdt_reset();
  
  // Go back to idle
  cc1101_WriteStrobe(CC1101_SIDLE);
  delay(5);
  
  // Long blink to indicate TX occurred
  digitalWrite(LED_PIN, HIGH);
  delay(300);
  digitalWrite(LED_PIN, LOW);
  delay(100);
  wdt_reset();
  
  Serial.println(" Done!");
  Serial.print("DS: "); Serial.print(dsTempC, 1);
  Serial.print(" BME: "); Serial.print(bmeSample.tempC, 1);
  Serial.print(" H: "); Serial.print(bmeSample.hum, 1);
  Serial.print(" P: "); Serial.print(bmeSample.presHpa, 1);
  Serial.print(" VCC: "); Serial.print(vccMv); Serial.println("mV");
  Serial.flush();
  wdt_reset();
  
  sleep_1s();  // Sleep for 1 second after transmission
}