[USRP-users] E310 RFNoC FFT Overrun Issue

Marcus D. Leech patchvonbraun at gmail.com
Sat Feb 9 09:11:29 EST 2019


On 02/09/2019 07:05 AM, Ramazan Çetin via USRP-users wrote:
> Hello all,
>
> I want to get fft of 50Ms/s signal and after fft using DDC i will pass 
> the samples with 1-5Ms/s to ARM processor.
>
> I have compiled an FPGA image with FFT, DDC and FIFO.
>
> |   |     _____________________________________________________
> |   |    /
> |   |   |       RFNoC blocks on this device:
> |   |   |
> |   |   |   * Radio_0
> |   |   |   * DDC_0
> |   |   |   * FFT_0
> |   |   |   * FIFO_0
>
> I have a gnuradio flowgraph (It is attached);
>
> Radio -> strToVector -> FIFO -> FFT -> vectorToStr -> CompToMag -> 
> NullSink
>
> When i used master clock rate 1M, there is no overruns. After 1M for 
> example (1.5M) i am getting overruns.
>
> [INFO] [E300] Performing register loopback test...
> [INFO] [E300] Register loopback test passed
> [INFO] [0/Radio_0] Initializing block control (NOC ID: 
> 0x12AD100000000000)
> [INFO] [0/DDC_0] Initializing block control (NOC ID: 0xDDC0000000000000)
> [WARNING] [RFNOC] Can't find a block controller for key FFT, using 
> default block controller!
> [INFO] [0/FFT_0] Initializing block control (NOC ID: 0xFF70000000000000)
> [INFO] [0/FIFO_0] Initializing block control (NOC ID: 0xF1F0000000000000)
> [WARNING] [RFNOC] Assuming max packet size for 0/FIFO_0
> Press Enter to quit: overrun on chan 0O
> overrun on chan 0
> Ooverrun on chan 0
> Ooverrun on chan 0
> Ooverrun on chan 0
> Ooverrun on chan 0
> Ooverrun on chan O0
> overrun on chan 0
>
> So, why is this happening? I thought i am handling data in FPGA so i 
> can get FFT of 50Ms/s signal. I just need to reduce sampling rate when 
> i pass the samples to ARM processor. What is wrong with my setup?
>
> Thank you. Best regards.
>
> Ramazan
>
>
Notice how there aren't strToVector blocks in the list of RFNOC blocks, 
nor complex-to-mag.   That means the samples are visiting the CPU
   at high rate.

The flow would be:

Radio-->FFT--->IIR_FILTER-->KEEP_1_IN_N--->then do the complex-to-mag on 
the host.

However, you're missing RFNoC blocks for the IIR filter and KEEP_1_IN_N





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