Hi, I have implement an FIR Low pass filter ons a MSP430F427A using SLAA357. I have successfully tested the filter. I later realized that for certain input values that the output of the filter is not correct. I tested the filter using the sweep data provided by the FIR code generator.
I then realized that this sweep data was 12-bit data. I read through SLAA357 again and saw that SLAA357 states that everything is done in terms of 12-bit A/D as it is the most popular. But in my case I have to use 16-bit data. I generated 16-bit sweep data and tested this and saw that the filter performs poorly. So it must be that the filter code generated is for 12-bit input values.
I have noticed that too a large value entered into the FIR filter causes the filter to saturate or overflow. Since the filter code is generated by the code generator after giving it the correct parameters including coefficients, I don't have a clue as to how I can fix this. My assembly is ok, so if someone could maybe explain the 12-bit code (FIR Filter) operation, then maybe I can adjust it for 16-bit operation. Maybe I can ask if it is even possible to get a 16-bit code generator?
I'm currently using a singed int as input value to the filter and it seems for values above 28000 and below -28000 that the filter overflows.
Any help or information will be appreciated.