// In setup()
    attachInterrupt(1, adcIsr, RISING);
}

volatile bool dataReady = false;

void adcIsr()
{
    dataReady = true;
}

loop()
{
    if (dataReady)
    {
        Serial.println(adc.readADC());
        dataReady = false;
    }
}

writeReg(OTP_B1, 0x30);
writeReg(PGA, PGA_OUTPUT_BUFFER_ENABLE | PGA_PGACHPDIS);