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LMX2492 EVM - Load Device Problems

Jessica Diller
Prodigy 30 points
Other Parts Discussed in Thread: CODELOADER, USB2ANY, LMX2492, LMX2592

I have the LMX2492 EVM. I set it up with a 5V power supply (Vcc_5V) and a spectrum analyzer (Rf out). I have the CodeLoader program up and running with the most recent update for the USB2ANY, which it connected from my computer to the board. I'm unsure where to go from here to start setting up data to be loaded onto the device. I understand that when I start switching the numbers in the buts/pins tab (VCO frequency, n counter, and numerator/denominator stuff) it should change the output frequency. I wasn't getting a change when I did change them though. I tried clicking "load device" in the keyboard control drop down menu as well as reload scripts multiple times with multiple set values. I then tried to check the communication of the device with my computer by setting the "powered down" option, which I read online should cause a decrease in current draw (lowered from 0.18). It didn't. I then unplugged the power supply and re-plugged it back in. Now the current draw is at 0.1 with exactly the same settings as before (set as powered down).

  • 0
    TI__Mastermind 28021 points

    Jessica,

    Here are some things you can try.

    1.  In the CodeLoader "Options" menu, ensure that "Elable Flex Scripts" is unchecked.   These are great to calculate ramping frequencies, but it slows down codelaoder and you can turn back on once you get things set up.

    2.   On the Port Setup tab, click "Identify".   This will blink the LED on teh USB2ANY board to confirm communication to the USB2ANY.   This does NOT confirm that the LMX2592 is responding to the USB2ANY, but a critical debugging step.

    3.  On the port setup tab, ensure that the settings are Clock Bit - 8, Data Bit-4, LE Bit - 2

    4.  On the EVM, ensure that there is an input signal that is required.  I know that there is an XO on the board, but it is not hooked up in default mode.   Although there is a microwire to load data into the shift registers of the device, I think  that the OSCin clock loads them from the shift register to the counters.

    5.  On the Menu, go to "Mode" and load the first default mode.

    6.  Push Ctr+L, or from the menu use "Keyboard Controls"->"Load Device".

    7.  The Power Up/Power Down test is good, but ensure that the SWRST bit is set to 0 and there is not something keeping the device powed down all the time.  I think that you are seeing the 180 mA from the VCO and our device might be powered down.

     

    Hope this helps.

     

    Regards,
    Dean

  • 0 in reply to Dean Banerjee
    Prodigy 30 points
    1. unchecked
    2. blinks
    3. settings correct
    4. I was reading documentation and it seemed like the XO on board WAS hooked up already in default with the inputs as options needing to be configured. I'm just trying to set the VCO frequency, n counter and fractional integration settings. This shouldn't involve the XO (I just kept it at the default setting of 100 MHz).
    5. done
    6. done
    7. I don't see a way to set the SWRST bit. It looks like there's just a check box. It's unchecked.

    Now I don't see any frequency on the spectrum analyzer. Or maybe a low one at like 400 kHz. This frequency still isn't changing when I change the VCO frequency input and then click "load device." I think you might be on the right track with the thought that the device might not be on, but it's plugged into power and the USB2ANY (thus the computer).
    Thank you for your response.
  • 0 in reply to Jessica Diller
    Prodigy 30 points
    Addition: the current draw has increasedto 27mA (from the original 18 or 10)
  • 0 in reply to Jessica Diller
    TI__Mastermind 28021 points
    Jessica,
    I think that having no OSCin signal is likely the issue. If there is no 100 MHz input, then the VCO tuning votlage will likely go to ground. This VCO on board is very badly behaved at low tuning voltages. Also, this OSCin signal is used to clock in the programming bits internally in our device, so the programming might not work correctly with no oscin.
    The instructions are confusing about the XO as they say it is optional to use a differential input, but this can be read as no input is needed; but this is not the case.
    The schematic on page 12 shows R21 and R28 to power and hook up the XO, but hte BOM on pages 14-15 show that these components are not stuffed.
    If it is possible to put any input signal or install resistors R21 and R28, then it would take thie OSCin out of the picture.
    Regards,Dean