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LDC1101 SPI problems

davide bellotti
Intellectual 350 points
Other Parts Discussed in Thread: LDC1101

Hi I have a problem with the comunication between the ldc1101 and pic 18lf4685 

ldc is 3.3 v supplied as well the pic , i try to send a simply command 0x3F for example but i not receive any  aswer from the ldc1101 .

Is there some command to start the comunication or some arrangement for the output of the sdo from the converter to the PIC?

thanks 

davide

  • 0
    TI__Guru* 92655 points
    Davide,


    I've moved this post to the Inductive Sensing Forum where the LDC1101 is supported. I'm sure you'll be able to find an answer here.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Genius 13650 points
    Hello Davide,
    we publish the firmware source code which you can use as a code example to get SPI communication going. The source code is automatically installed in the Firmware sub-directory of the LDC1101 GUI.
    I'm afraid we only provide firmware for the MSP430 and not for a PIC.
  • 0 in reply to Ben Kasemsadeh
    Intellectual 350 points

    Mr Ben , thanks for your answer , I have two questions

    1st how    can I open and read the source code example , do you have a C++ code  please?

    2nd , I can send commands  from the pic to the LDC1101  , I can start and stop it  , I see that reading the frequency in the coil  but i don't have any signal 

    output from the sdo pin. It is always low , not tristate  or high. 

    thanks 

    best regards 

    davide

  • 0 in reply to Ben Kasemsadeh
    Intellectual 350 points
    Hello I forget a question , I am working with a 8 bit microcontroller so the spi train pulse is spitted in two trai pulse each of 8 bits . that can affect the receive data? thanks
  • 0 in reply to davide bellotti
    TI__Genius 13650 points
    Hello Davide,
    1) we only have the C firmware source code that is provided as part of the GUI.
    2) are you following section 8.5 and the SPI timing diagrams from the LDC1101 datasheet?
  • 0 in reply to Ben Kasemsadeh
    Intellectual 350 points

    Hello Ben ,

    I followed the istructions of 8.5 section , i can write to the device but  i can't read any data from sdo. 

    I tried to read DEVICE-ID   0x3F register but not answer .Supply is 3.3 v, frequency cklin = 16 Mhz  ,spi speed is very low.

    All the circuit is supplied 3.3 v also the spi . I send  two bytes 1st send the command and the second read the data.

    SDO is always low state not change.

    thanks .

  • 0 in reply to davide bellotti
    TI__Genius 13650 points
    Hello Davide,
    I looked into your PIC. It has a hardware SPI interface, so you should simply need to write commands to the PIC which execute the SPI transactions. It is unlikely that it is a software issue. Please verify hardware connections of the SPI bus, and ensure that voltage levels match. If you don't find the issue, please post a scope plot of the SPI signals and the section of the schematics which show the PIC and LDC.
  • 0 in reply to Ben Kasemsadeh
    Intellectual 350 points
    Hello , Ben thanks I will check it and if i not have a solution I will send a plot
  • 0 in reply to Ben Kasemsadeh
    Intellectual 350 points

    hello MR Ben, no result from  my test  I send you a picture of my scope unfortunatly  it has only two tracks , in this case  i try to send a start command

    0x0B  byte with 0x00 byte and  read a value in 0x23 . CS is tied low during the commands and sdo is always  low .Please can you send my a spi image  of your scope sending a  command for example start command and values read command so I can copy in my software? thanks. best regards.