SEm/escapeLab/signal generator
From FSI

Welcome to the SEM escape lab
5th and last Key
Matching the waves
Find the coefficients and match the signal.
Specifications
4 sinewaves are combined to build a signal:
 the frequency of the second one is the double of the first one's.
 the frequency of the third one is the double of the second one's.
 the frequency of the fourth one is the double of the third one's.
Each sinewave is damped by a power of 2 : in terms of hardware, the signal values are shifted to the right by a given number of bits. The damped sinewaves are then added together to form the signal at the bottom of the following picture.
Damping factors can either be 1, 1/2 and 1/256. The key is the modulo 30 sum of:
 the power of two of the first coefficient (0 for 1, 1 for 1/2 and 8 for 1/256)
 two times the power of two of the second coefficient
 three times the power of two of the third coefficient
 four times the power of two of the fourth coefficient
PS: 1st coefficient is 0