function write_volt(v)
	global ser;

	p = volts_to_pwm(v);
    fprintf(ser,'%04X\n', p);		% send a pwm value to controller
	drawnow;
end

function p = volts_to_pwm(v)
global V_max
% volts_to_pwm - convert volts to PWM value

	p = v * (32767/V_max) + 32768;
    p = round(p);
    
end