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Product and design recommendations for ~65 MSPS signal processing system

Fredrik Lundqvist
Prodigy 245 points
Other Parts Discussed in Thread: TMS320F28335, ADS62P42, OMAP-L138

Hello,

Currently I'm in a project where I'm building a prototype to oversample a signal around 5 MHz and perform signal analysis on a DSP. My previous equipment was a TMS320F28335 experimenters kit with an internal 12-bit 12.5 MSPS ADC. Now I would need a memory upgrade and a better external ADC (no DSP with internal ADCs exists with more RAM and sample rate). I've made a post in the microcontrollers forum (http://e2e.ti.com/support/microcontrollers/c2000/f/171/t/246037.aspx?pi239031349=1), but thought that this forum would have better ideas regarding the ADC and how to connect it.

Because I think that 12-14-bit 65 MSPS would be enough and will not give me too much data to handle, I've looked into ADC specs similar to that. But you should know that I have no experience in this field other than that I gained by using the F28335. Because I'm more on a time budget than a price budget, I'm thinking of evaluation modules to get rid of hardware troubles. One example is the ADS62P42 evaluation module. How could this be connected to a DSP (e.g. C2000/C6000 family experimenters kit)? From what I've understood, a 65 MSPS sample cannot be pipelined directly to a DSP because of lack of CPU speed? With this in mind, I found the low cost capture card TSW1405EVM. This can save 64 kB of the sampled signal, which in my case would be enough (I expect only ~6000 samples).

Is a possible combination a ADS62P42 to sample the signal, a TSW1405EVM to connect to the ADC and save the sampled signal, and then a DSP (e.g. C28346 experimenter's kit or similar) to retrieve this signal in order to perform signal processing? How much work would it require to put this all together? My thought was that because they are all evaluation modules and experimenter's kits, it would simply be some wiring and programming. In the end, I want the DSP to be the master, i.e. to initiate when the ADC should start sampling and for how long (with an ADC internal clock). This must be driven by the DSP code without PC software GUI.

Any other ideas of what I can do is also much appreciated.

Best regards,

Fredrik

  • 0
    Prodigy 245 points

    I found a thread (http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/p/193799/699365.aspx#699365) mentioning the uPP interface to connect to high speed ADCs. This seems to be available with the C674x/OMAP-L1x devices. Could this be a solution to directly connect to e.g. the ADS62P42 evaluation module? After some reading I have the impression that the TSW1405EVM is designed to interface directly with a PC, not a DSP or similar device.

  • 0 in reply to Fredrik Lundqvist
    TI__Genius 12965 points

    Hi Fredrik,

    The UPP interface/protocol of the LM1xx may not be compatible with the parallel CMOS interface of the ADC.  This is something that the DSP LM1xx folks may have to confirm to see if the timing diagrams line up (basic parallel CMOS interface).  This is not something we have ever tried.

    The TSW1405 is meant to be driven off the USB port of the PC using a simple USB to SPI interface for JTAG (program the FPGA) and register control.  We have a DLL for the PC for this purpose, but not something we have tried with embedded applications.

    Ken

  • 0 in reply to Ken C
    Prodigy 245 points

    Thank you for your reply. But according to this link (http://processors.wiki.ti.com/index.php/C6748/46/42_Complementary_Products#Analog-to-Digital_Converters), the C6748 included in the OMAP-L138/C6748 experimenter's kit should be compatible with direct connection to ADCs through the UPP interface. However, if there is no simple way of connecting these components without some serious circuitry on a PCB board, that is still not a viable option for me.

    Is there no simpler way (premade solution) than via FPGA and to put all the components (no EVM) on a chip myself?

  • 0 in reply to Fredrik Lundqvist
    TI__Genius 12965 points

    Frederik,

    This compatibility list looks like it was comprised based on the CMOS interface specs in the datasheet - we have not physically tested the L138 UPP to the EVMs listed in the link.

    However a third party has implemented this interface on their development board and connected the L138 to one of our CMOS ADC EVMs via a ribbon cable.  It looks like it will meet your needs for embedded applications.

    http://www.mitydsp.com/upp

    This looks like a good start since it already has the CMOS header to connect to all of our CMOS ADC EVMs.

    Ken

  • 0 in reply to Ken C
    Prodigy 245 points

    I ended up buying the OMAP EVM kit. It is a ready to go solution and with possibilities of expansion e.g. via the uPP interface to a better ADC. Thanks for your tips!