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Hot!Advice on receiving high speed parallel data

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hevats
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2019/10/21 22:02:34 (permalink)
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Advice on receiving high speed parallel data

We are working on a project where we have to interface with a FT2232H. The FT2233H has multiple asynchronous and a synchronous FIFO mode. Our aim is to receive the data at about 7MBps into our device (PIC32 or DSPIC24E or whatever suits). So far we have been working with the asynchronous FIFO mode, bit banging and reading over parallel. We only manage to reach about 6MBps before data corruption kicks in. The max asynchronous rate as per FTDI datasheet is 8MBps, which would be in ideal conditions, so probably we are hitting the limits here. On the other hand the synchronous mode operates at 60MHz, I'm not sure if we could read that fast. All advice is welcome!
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    NorthGuy
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    Re: Advice on receiving high speed parallel data 2019/10/22 07:37:52 (permalink)
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    Synchronous transmission is much more reliable.
     
    If your PIC can do 30 MHz slave SPI, you may Consider MPSSE mode. Wire CLK/TDI to one SPI module. Wire CLK/TMS to a different SPI module. If you solve the synchronization problem, it'll give you 2 x 30 / 8 = 7.5 MBytes/sec.
     
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    hevats
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    Re: Advice on receiving high speed parallel data 2019/10/22 19:22:58 (permalink)
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    Good idea, I'm not sure about the host side drivers though. If I understand correctly this would require both channels of the FT2232 with the data being split and then re-assembled somehow on the PIC side...
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    NorthGuy
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    Re: Advice on receiving high speed parallel data 2019/10/22 21:49:30 (permalink)
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    hevats
    Good idea, I'm not sure about the host side drivers though. If I understand correctly this would require both channels of the FT2232 with the data being split and then re-assembled somehow on the PIC side...



    No, that's only one channel. MPSSE will produce 2 SPIs with the same (shared) clock.
     
    Although you can use two channels as well (each with its own SPI).
     
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    hevats
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    Re: Advice on receiving high speed parallel data 2019/10/23 06:15:25 (permalink)
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    That just went over my head... I only could find one SPI per channel

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    NorthGuy
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    Re: Advice on receiving high speed parallel data 2019/10/23 06:47:57 (permalink)
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    hevats
    That just went over my head... I only could find one SPI per channel



    You use pins 32 and 33 for one SPI, and pins 32 (same clock as the first SPI) and 35 for the other SPI.
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    NorthGuy
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    Re: Advice on receiving high speed parallel data 2019/10/23 15:58:15 (permalink)
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    On a second thought, the MPSSE commands are quite clumzy and there might be not enough USB bandwidth for bit-banging both TDO and TMS pins at 30 MHz. Using two channels for two SPIs is a better idea.
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