This was a long time ago, so forgive me if I forget my reasoning here, but I think this refers to the fact that it's an 8 bit ADC. We want an RMS output in the range -1 to +1.
Jason On 11 Mar 2013, at 15:21, Pam Ford wrote: > Hello, > > In tutorial 4 (pocket correlator) the python file poco_adc_amplitudes.py reads > the values from the adc_sum_sqN registers and calculates the RMS as: > > inputs[input]['unpacked'] = fpga.read_uint(regname) > inputs[input]['rms'] = > numpy.sqrt(inputs[input]['unpacked']/(2.0**16))/(2**(8-1)) > > I believe "numpy.sqrt(inputs[input]['unpacked']/(2.0**16))" calculates the > RMS, but why is this divided by (2**(8-1))? Is this just a scale factor, and > if so, how was it chosen? > > Thanks, > Pam Ford > > >
