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  • Floating Point Coprocessor Question

    I was wondering if anyone has had any experience using Micromega's 32 or 64 bit FPU in conjunction with the Picasso GFX or SGC units?

    I have a graphics application that will require 9 significant decimal digits of accuracy in the calculations leading up to the display rounding. Unfortunately I cannot cut back on the preceding calculations or I will have significant errors in the display.

    In particular, I was wondering about the I2C interface and whether anything special had to be done or whether the built in GFX functions for I2C worked out of the box.

    Thanks in advance for any comments or assistance that anyone might be able to offer.

    Regards,

    Geof

  • #2


    If you are using Micromega's 32 or 64 bit FPU as a host, I would presume that all your number crunching will be done in the host,
    and you will be using the display for printing numbers to screen, drawing objects etc.
    If so, all results etc can be just printed as strings, and all graphics will only require integer values regardless.

    I2C should work ok 'out of the box' - theres quite a few examples available,
    however, bare in mind that if you need to do anything other than 16bit integer math
    you are best off connecting the sensors to the mega, unless you specifically want the sensor at the display end
    (in this case you can treat the display as a remote data aquisition system, get the data up to the host, then send back the processed info)
    Regards,
    Dave

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    • #3


      Thank you, Dave. I should have been a little clearer. I am planning to use the uLCD-32PT-GFX2 as the host. As I require calculations, I will send the request to the uFPU-64. It is my understanding the the uLCD-32PT can only act as an I2C MASTER and not as a slave.

      I was mainly concerned with the I2C commands coming from the uLCD and wondering if they would need any "tweaking" to work with the uFPU. From reading the manuals I would doubt it, but thought if anyone had any actual usage experience I would appreciate knowing beforehand about any problems. Micromega has a very detailed step-by-step procedure for setting up the interface. I told them that I would keep them posted on my progress. Cam Thompson at Micromega is excellent to work with based on my past experience.

      FYI I am planning to use the RTC built into the uFPU to be the base of a "real time" display of the sky based on my location in NM. A lot of detailed calculations are involved that just seemed beyond the integer math of the uLCD.

      Thank you again for your comments.

      Regards,

      Geof

      Comment


      • #4


        Although it would be possible to use uLCD-32PT-GFX2 as the host for your requirement, I would strongly suggest using serial for your comms back to the uFPU-64.
        2 reasons - comms is non blocking and can be treated as a background buffered service running a simple packet based communication scheme, and also, this will free up the I2C port on the uLCD-32PT-GFX2 for sensors only.

        And yes, I2C is master only, and blocking - so if there is a lot of sensor intervention it would really bog things down (and possibly have priority issues) if you were using I2C for both.

        No problem displaying (almost) realtime info back from the uFPU-64 this way either.

        If you were to make yourself a little packet system, similar to prophibus or modbus you can create a very efficient system.
        Regards,
        Dave

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