void sim_bmp() {
    int simulated_pressure = sim_pr.toInt();
    float sim_alt = bmp.readAltitude(simulated_pressure/100);
    float og_alt = bmp.readAltitude(calibration);
    packet += String((og_alt-sim_alt), 1);
    packet += ",";
  
    packet += sim_pr;
    packet += ",";
  
    float sim_temp = bmp.readTemperature();
    
    packet += String(sim_temp, 1);
    packet += ",";
  
}