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LP55281: LP55281 EVK issu

Wesley Lai
Intellectual 290 points
Part Number: LP55281

Dear Sir,

I have two sets of EVKs for the LP55281. I am currently using the PC for EVK testing and found some problems:

1. When the EVK is connected to the USB of the PC, press the Start Test button on the LED test page, we can see that the LED on the EVK is light-on, but the USB status in the upper right corner of the software will display... "USB error 84", this time LED Still bright, but we can't control the EVK. When we remove the USB and reinsert it, we can control the EVK, but after pressing the Start Test, the EVK will crash.

My operating system is WINDOWS 10. I don't know if the problem described above is wrong.

2. In addition, I tried to separate the EVK and use the MCU to provide the SPI signal to the upper LED board. I found that it could not be light-on. The signal given is correct and all connection are correctly, but it cannot be light-on the LED. Then I tried to connect the two boards of EVK with DuPont wire, the SPI signal separately and connect it to the MCU, so that the LED can be light-on normally. We confirmed the EVK circuit diagram on the documentation and the connection between our SPI and the MCU and found that they are all correct.

In the EVK's description circuit, what signal is not indicated in the circuit diagram?

  • 0
    TI__Intellectual 950 points

    Hi,

    We did find that the GUI of LP55281 EVM has some compatibility problems in WIN10. Since it is developed under early windows environment. If you can find some computer with old windows system, please use that computer to operate the EVM.

    LP55281 is a LED driver with I2C and SPI interface. Do you try to use MCU I2C to control the LED board to double check connection is correct?

  • 0 in reply to Rosley Ge
    Intellectual 290 points
    Hi Rosley,

    Thank for your reply.

    I had a computer is operation WIN 7 64-bit environment, I try to control EVM by using that, and the result same the WIN 10.
    The GUI of LP55281 EVM can operate in Win XP ?

    No, because we will using 6pcs LP55281 to light-on 24pcs RGB LEDs, if using I2C interface, the LP55281 it can not support many ICs.
  • 0 in reply to Rosley Ge
    Intellectual 290 points

    Hi Rosley,

    We have another questions about the LP55281.

    The first question:

    What is the SPI mode of this IC ? Rising or Falling ?

    SPI Timing Chart

    Th second question:

    The reset signal is generated from our MCU, and the wavefront is attached PNG file.

    The color yellow is SS signal.

    The color blue is SPI clock.

    The color pink is SPI data.

    Now, we use this wavefront to reset the LP55281, and we send the other command, the LP55281 can not work.

    The picture show the clock timing is 984ns, we think it is on the spec, right ?

  • 0 in reply to Wesley Lai
    TI__Intellectual 950 points
    Hi,
    You can refer to datasheet page 9 for SPI timing. It should be rising edge.
    As for second questions, 984ns is allowed. I am not sure what's the problem here. What command do you send after reset?
    Thanks,
    BRs,
    Rosley