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ADC12J1600EVM: using pin headers to program ADC and LMK with SPI instead of FTDI + GUI

Intellectual 270 points

Replies: 15

Views: 172

Part Number: ADC12J1600EVM

Hi,

I want to use the pin headers on the board to connect an FPGA board and program the devices externally using SPI over the connectors

instead of using the FTDI chip apart from connecting some wires , do i need to mod the board in anyway?

also have wired up the correct pins on the header for LMK SPI?

Regards,

Charles

  • Guru 69660 points

    Charles,

    For the ADC, you need to remove R118, R110, R111, and R109. These are located on the top side between U12 and the connector.

    For the LMK and TRF3765, you need to remove R68, R113, R114 and R115. These do not have silkscreen but are identified in the attached picture.  

    Your connections shown look correct as far as I can tell.

    Regards,

    Jim

    R115, R68, R114 and R113.pptx

  • In reply to jim s:

    Hi Jim,

    so i have removed the resistors as you said and connected up both headers i have, my FPGA is writing all the registers in the same order as the GUI (using the config files as a guide) and also each SPI interface is copying the pattern files also supplied with the GUI

    Nothing is happening.

    the LMK/TRF header i'm using 3.3v volt pins from FPGA

    the ADC i'm using 1.9v pins (actually its 3.3v out of the FPGA) but i'm going through a level shifter.

    I'm a missing anything?

    i have a logic analyser which i used to capture the FTDI transfers (we have 2 ADC boards) and i'm pretty sure the protocol is the same.

    one thing i noticed is if i probe the other side of the 12.4k resistors with logic analyser its seems to not pick up the signals properly, they seem like quite large resistors could that be an issue?

    Regards,

    Charles

    P.S i got all the jesd stuff from other thread working!

  • In reply to Charles Shaw1:

    Hi Jim

    so am able to talk to the LMK04028 ok

    i'm not seeing any clocks coming being activated though would that be the TRF3765

    Regards,

    Charles

  • Guru 69660 points

    In reply to Charles Shaw1:

    Charles,

    The SPI for the TRF3765 works differentially than the other parts. Is your interface following the protocol as shown in the attached document?

    Regards,

    Jim

     TRF3765 SPI.pptx

  • In reply to jim s:

    Hi Jim,

    i don't think your right there 

    it seems to be the same to me the latch enable is basically just the slave select.

    below is a capture from FTDI to TRF3765  thsi is register 9 being written:

    i'm running the SPI at 20Mhz which is its top rated , i noticed the FTDI runs at a slower frequency about 3.125Mhz

    so might try at a lower frequency

    Regards,

    Charles

  • Guru 69660 points

    In reply to Charles Shaw1:

    Charles,

    Not sure what you meant by "I don't think you are right there". What Is sent was directly from the data sheet. Are you saying you are following this protocol and my guess at your problem was incorrect? If so, have you tried running your SPI at a lower rate? Did this help?

    Regards,

    Jim 

  • In reply to jim s:

    Hi Jim,

    so i ran at 10Mhz and still the same result i can write/read the lmk ok , but the TRF and ADC seem unresponsive

    i'm following the datasheets for all the devices , plain and simple it should work buts not working

    the ADC and LMK have exactly the same protocol and yet one works and one doesn't (same code for both)

    am stumped 

    Regards,

    Charles

  • Guru 69660 points

    In reply to Charles Shaw1:

    Charles,

    From your last response, I cannot tell which part you are having success with. I am guessing the ADC only. The LMK defaults to 3 wire SPI mode at power up. We have to change this 4 wire SPI mode to get a valid read back with our GUI. For your other issues, You should just be able to repeat what the FTDI and GUI does. Are the voltage levels correct?

    Regards,

    Jim

  • In reply to jim s:

    Hi Jim,

    no i said i can talk to the LMK

    but not the ADC or TRF

    the voltages are 1.9v for the ADC header 

    And 3.3v for the LMK/TRF

    I've also tried altering the slew rate, too no effect.

    just tried running the interface at 6.25 Mhz but again no joy.

    Regards,

    Charles

  • Guru 69660 points

    In reply to Charles Shaw1:

    Charles,

    For the ADC, make sure you are sending CS low when SCLK is low. I don’t think the ADC will respond if CS goes low when SCLK is high.

     

    The detailed SPI spec from the digital team is attached. The drawing in the ADC12Jxx00 datasheet doesn’t show this well/properly.

    Regards,

    Jim

     SPI Timing diagrams.docx

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