It is possible to use a function generator for testing purpose. If the user attaches a function generator between VO_DAC and GND, then the output from the DAC is overdriven and the function generator now provides the reference to the converter for the haptic signal. The user still has to set up a haptic event using the digital registers as they would normally to create a haptic event. In terms of magnifying the reference, the transfer function from reference to output is as follows: VOUT = REFERENCE *2.818*(RFB1+RFB2/RFB1) = REFERENCE*2.818*(715+20)/20 = REFERENCE * 103.5615. Therefore, to produce a 40V signal, a reference signal of 0.386V should be used.