recently, i am using the C5515 USB Stick demo board for developing ultrasonic signal sampling, heterodyning ,filtering, and outputing to headphone. now i am in some trouble.
the orignal ultrasonic input sampled signal is centre frequency of 40KHz with + - 2.5KHz bandwidth, the general process is as this: first, i am using the IAC3204 's ADC to sampling the input ultrasonic signal, then i transfer it into the C5515 DSP by I2S interface, and DMA will move the data from I2S's receiving register to the memory for heterodyning and bandpass filtering, and the filtering is demanded to be real time processing, the signal after filtering processed will transfer back to AIC3204's DAC also by I2S interface, then after AIC's DAC processing, the signal will then output to the headphone.
i have two unsloved questions:
first, the AIC3204 doesn't seam supporting the 40KHz signal , i mean ,although it supports 192KHz's sampling rate, but it's dedicated to audio signal processing, and its interal decimation filter - C Filter will cut off the frequency at 20KHz, this is not good for my ultrasonic signal ?
second, every 48 samplings as a frame, i do data processing every frame, if the sampling rate is two high, like 500KHz or more than that, then the left processing time for DSP to do heterodying (multiply a cosine function ) and bandpass filtering . (for example ,if the sampling rate is 100KHz, then sampling 48 values will take 48/100,000 , and this time span is for DSP processing the last frame signal, so the DSP must finish the data processing before sampling frame signal finished , if i use 200KHz, the time span will be half of 48/100,000), during this signal processing , i used two methods heterodying and bandpass filtering , heterodying is for changing the sampled ultrasonic signal into human ear available audio, i used multipling a cosine function to do so, and the filter is used convolution in time domation. and i know these two are time-counsuming. how fast sampling rate can C5515 stand ?
by the way, i has finished to do so by C5515 demo board towards recorded audio( i mean the ultrasonic signal has been heterodyned into audio range, and i recorded it , so i used jack connection my PC's line-out to my DSP board's LIne-in, and play it out using my PC, and my board's line-out is connected to my headphone,then i can hear the process result. note :sampling rate is 48KHz, 48 samples as a data processing frame)
1、dose TI has some supper IC that is suitable for my design demands above
2、or can soemone give me some prevcious recommedatons,like some other combination of TI's IC or solve tips ?
thanks
