ESP8266 SPI spy sync pin interrupt

sync_isr.cpp

int   voltint = 0, currentint = 0, wattint = 0;       // raw values

void ICACHE_RAM_ATTR sync_isr() {                           // Sync pin interrupt on falling edge
  SPI1S |= SPISSRES;                                        // Reset HSPI slave
  SPI1S &= ~SPISSRES;
  SPI1CMD = SPICMDUSR;                                      // Start HSPI slave
  static bool glitch = false;
  if(data_ready) {                                          // If a data has been received by the HSPI
    data_ready = false;
    int volts = (data[0] << 16) + (data[1] << 8) + data[2]; // assemble 24 bits
    if(volts > 5 * voltint / 8 || glitch) {                 // reject samples that have been shifted right by noise on the clock line?
      glitch = false;                                       // sample accepted
      voltint = volts;
      currentint = (data[4] << 16) + (data[5] << 8) + data[6];
      wattint    = (data[8] << 16) + (data[9] << 8) + data[10];
      if(wattint > 0xFF0000)                                // sometimes goes slightly negative with no load
         wattint = 0;
      ++samples;
      new_readings = true;                                  // new raw readings ready
    }
    else
      glitch = true;                                        // only reject one sample
  }
}