45/512 degrees per 0-512 values, so calculate the equation Tricky supplied based on increments of 45/512 degrees then scale everything accordingly to the bit width of your LUT.
45/512 degrees per 0-512 values, so calculate the equation Tricky supplied based on increments of 45/512 degrees then scale everything accordingly to the bit width of your LUT.
I just realized this doesn't answer your original question...
You are trying to implement a lookup table that has only ATAN defined for 0-45 using a 512 entry table, which you use to produce a -90 to +90 output, which are the limits of the ATAN function. This probably can't be done as ATAN on the X axis goes from -infinity to +infinity and produces the output -pi/2 to +pi/2. Tricky's equation appear to be wrong. See the following graphs of the arctan funciton.
The only way to reduce an ATAN function LUT is to produce a table that has the last value at the limit of your resolution for pi/2 down to 0 and then use either negative values of this table or the positive values depending on the sign of the input, i.e. you can only reduce the size of the table by 2.