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  • PerM's Avatar
    11-21-2021, 07:15 PM
    It seems like arm_rfft_fast_f32 is indeed supported! And it can handle the following FFT lengths: 32, 64, 128, 256, 512, 1024, 2048, 4096. This is great since it means I can write code that can easily support a few...
    5 replies | 352 view(s)
  • PerM's Avatar
    11-16-2021, 08:21 PM
    Thanks Mark! You are right that my input data is real, so rfft functions would be a better choice than cfft. But I do want to use floats and the arm_rfft_init_f32/arm_rfft_f32 functions do still seem to have the...
    5 replies | 352 view(s)
  • PerM's Avatar
    11-15-2021, 09:20 PM
    The analyze_fft1024.cpp/h class uses arm_cfft_radix4_q15 from an old version of CMSIS. There is a corresponding function for f32, which is what I am interested in here. In the old CMSIS functions, it seems like 256 and...
    5 replies | 352 view(s)
  • PerM's Avatar
    11-14-2021, 12:11 PM
    Interesting. Maybe it would be a good idea to include this as a standard feature in the I2S audio blocks as it seems like at least the both of us, and presumably more people, sometimes have the need? I guess one...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-12-2021, 06:07 PM
    I might have solved it or at least found a workaround. I added a state variable to my input_i2s_quad class that controls whether or not the isr() routine should call update_all() and copy data from the DMA buffer. ...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-11-2021, 07:55 PM
    The frequency shifting and filtering is done by code from the AudioSDR project, https://forum.pjrc.com/threads/57362-AudioSDR-A-single-Audio-block-SDR-(software-defined-radio)-processor-demodulator It is actually even...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-11-2021, 04:54 PM
    As I have probably already mentioned, measuring the phase difference between the two RF signals is pretty much the most important function of this project, so it is not just something I added as a quick debugging test....
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-10-2021, 08:51 PM
    This might not be perfectly intuitive, but the math works out the way I tried to describe. So while I am indeed measuring the change in phase differences between the IF signals for two different LO frequencies, the...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-09-2021, 08:13 PM
    Sorry if I was unclear and thanks for asking for clarification. I have two WM8731 codecs. As you suggested, I rewired my board so that both are driven by the I2S1 clocks from the Teensy while the ADCDATA signals are...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-09-2021, 07:48 PM
    Not a complete answer, but perhaps a start: In this post: https://forum.pjrc.com/threads/68591-Synchronizing-the-two-I2S-ports-on-Teensy-4-0?p=293023#post293023 I have shared some code that sets up the DMA engine to...
    4 replies | 309 view(s)
  • PerM's Avatar
    11-09-2021, 07:34 PM
    I was a bit too hasty in my conclusion of having solved the phase offset problem between the I2S inputs. It turns out that I often do not get the desired synchronization between the two I2S inputs. After some...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-04-2021, 08:49 PM
    Thanks everyone who helped! I patched my board so that both codecs are clocked by I2S1 while the ADCDATA signal from the second codec is connected to pin 6 of the T4. Fortunately, this pin was not used for anything...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-02-2021, 05:24 PM
    Neal, I think you will need to dig into the big "i.MX RT1060 Processor Reference Manual". Sections 11.7.353 - 11.7.356 tell you to which pins you can mux the SAI1 (I2S1) data input pins. E.g. RX_DATA1 can be muxed to...
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-02-2021, 07:43 AM
    Thanks WMXZ! You are probably right that that is a better approach. I will look into it and probably patch the board and modify the software.
    21 replies | 1079 view(s)
  • PerM's Avatar
    11-01-2021, 10:17 PM
    I am working on an SDR project where I need to sample and then synchronously process two IQ IF signals using WM8731 audio codecs. I have the codecs and RF parts working fine, but I have not yet found a way to reliably...
    21 replies | 1079 view(s)
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