MSP430FR6047: MSP430FR6047

Tool/software:

Hey,
I have a question on MSP430FR6047. 
the Pipe uses 500kz as Frequency. the signal looks good but the biggest part is negative. 
how can i center the signal arround 0? i think this the problem why i don't have a working Flowmeasurement. 

i tried changing USS_HSPLL_FREQ_IN_MHZ and USS_SDHS_OVER_SAMPLE_RATE and some other parameter but nothing changed. 

i'm using USS_Capture_Gain_Range_27_7 as Amplification in casa that might be the problem. 

but when i also use lower amplification, the signal is small but not centered. 

thank you for support.