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LP8556: I2C communication is ok ,but the registers value didn't changed

Fandy
Expert 2285 points
Part Number: LP8556

Hello

when I used pre-configuration for PWM dimming version LP8556SQE-E00, LEDs dimming function is ok when using PWM dimming ; but actually I need to control by I2C;

so which register & EPROM need to be change ?

I think 01h bit "FAST" "BRT_MODE" and A2h bit "BL_ON" need to be change , so I re-write it , but cann't write successful, the value of 01h ,A2h I read  is the same default value.

it could be caused by what ? expect your reply 

  • 0
    TI__Mastermind 22745 points
    Hi Fandy,
    Yes, I get your question, your understand is totally right, it should be re-written when you change the regs, can you chekc the hardware connection? and you can try again, can you make sure your I2C communication signal is right? have you obaerved the SCK and SDA signal ?
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 2285 points
    Hi Sean
    if any other registers should be change except I mentioned before ?
    I think hardware is ok , three board cannot change registers,and obzerved SCK.SDA waveform has no problem ,but cannot change registers successful. did LP8556 need unlock first?
  • 0 in reply to Fandy
    TI__Mastermind 22745 points

    Hi Fandy,

         No, LP8556 don't need unlock first, could you use our GUI to check whether you can read the regs has changed after you change the regs as bleow:

         

    Regards

    Sean

  • 0 in reply to Sean Zhou
    Expert 2285 points

    Hi Sean

    By the way, there is a power reset operation after I2C communication,actually registers already renewed  , then it reset to default value after power reset .

    What confused me was that Register 's value reset is make sense ,but EPROM's value should be maintain in configured value after power -off , like A0h /A1h ; 

  • 0 in reply to Fandy
    TI__Mastermind 22745 points
    Hi Fandy,
    LP8556 has the EPROM not E2PROM, after power off the regs will reset to the default value, it's that make sense to you? So that's the problem for your phenomenon, because you have reset the device, so the regs have also been reset.
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 2285 points
    Hi Sean
    EPROM and EEPROM are all should be Non-Volatile Memory ,so the data shouldn't be lost , isn't it ?
  • 0 in reply to Fandy
    TI__Mastermind 22745 points
    Hi Fandy,
    Yes, EPROM is the old technology and it can't be re-write just with electric signal. EPROM is the new tech, and you can just use I2C to re-write. Our LP8556 is EPROM and when you power off , it will be rest to default value. Please refer to google for some description about EPROM and E2PROM.
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 2285 points
    Hi Sean
    LP8556SQE-E00 default is adaptive boost control ? Manual control or Adaptive boost control depended on AAh bit ADAPTIVE ?
    output connecting 8 series/string 3V LEDs total about 24V, but actually the Vboost voltage is about 34V, and LED1-4 PIN about 11V,it seems no adaptive boost control ,and Vboost voltage could manual set down by A9h
  • 0 in reply to Fandy
    Expert 2285 points
    Hi Sean
    Have any comments about last post?
    and the other strange thing is that LP8556SQE could directly dimming by I2C and PWM both without any register change, is it normal ?
  • 0 in reply to Fandy
    TI__Mastermind 22745 points
    Hi Fandy,
    Yes, LP8556 is adaptove boost control, normally we need enable the "ADAPTIVE" bit( reg AA bit 3). For your phenomenon, you have observed 34V ? What your regs seeting with regs A9H? it seems you have set with VBOOST_MAX to 101? In this situation , it seems that you have achieved Open? have you find any error when you observed 34V?
    And I don't understand what's your mean of "LP8556SQE could directly dimming by I2C and PWM both without any register change"?
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 2285 points

    Hi Sean

    LP8556SQE 's AAh is default value “0Fh”,(bit 3 is "1") , A9h default value is “A0h”，Vboost_max is "101" for 34.5V, and observed 34V at Vboost, no find other error;    Vboost voltage could manually set successfully by A9h.

    "LP8556SQE could directly dimming by I2C and PWM both without any register change"? I mean that LP8556SQE is pre-programmed for "PWM ONLY" version, is right ? LP8556SQE could dimming by I2C just only after change some regs,like reg 01h ?  but it could also dimming by I2C with no any program regs

  • 0 in reply to Fandy
    TI__Mastermind 22745 points
    Hi Fandy,
    If you want to use I2C, you need to change reg 01H(BRT_MODE), because LP8556SQE has been pre-configured with only PWM dimming. For 34V volatge, I suggest you check the LED spec and when you change the dimming code or duty cycle, have you observed any output voltage change? Thanks.
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 2285 points
    Hi Sean
    We think we have found the problem about no adaptive boost voltage regulation, it maybe need disable un-used led string, because my application is LED5,LED6 unused, after changed Reg A16h from default value 3Fh to 0Fh ,then it could adaptive voltage regulation.

    but about Dimming type, strange thing is it could be both PWM and I2C dimming with no change Reg 01h(BRT_MODE)
  • 0 in reply to Fandy
    TI__Mastermind 22745 points
    Hi Fandy,

    That's the good news, the dimming is a little stange, I will try to try with our EVM and response to you later. Please help me click"Resolve" button. Thanks.

    Best Regards
    Sean