• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 287 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DDC264: Read data from DDC264 via MCU with SPI

Ildar Rakh
Prodigy 20 points
Part Number: DDC264

Tool/software:

Hello, I have created a new PCB board with MCU and DDC264. I wanted to establish communication via SPI and start reading data. Currently, I want just only check that my design is correct. 

In my vision, I want to read data without writing any registers.  

So does it work the next protocol to read data?

I connected the next pins via the SPI protocol 

  • SPI CLK (MCU) to DCLK 
  • MISO (MCU)  to DOUT 
  • GPIO input (MCU) to DVALID 

So what was done from me 

1. Wait when via GPIO (MCU) when DVALID fall down from 1 to 0

2. Make a command to read via SPI 128 bytes 

This is right?

Regards, Ildar 

Regards, Ildar

  • 0
    TI__Prodigy 740 points

    Ildar,

    Thanks for reaching out!

    To confirm, yes, when DVALID is asserted low, the latest capture is ready to be read via SPI. 

    Your SPI connections look good, and assuming the CLK and CONV pins are connected, reset is the only pin missing. Asserting reset on a power-up is recommended (Section 8.5.1). As long as the default configurations are acceptable, there shouldn't be any need to update them.

  • 0 in reply to Shane Aspenwall
    Prodigy 20 points

    Thank you so much for your message, I can receive data now. Can you clarify where I can find the steps manual how to convert digital data to current?  So how to understand that for 16 bits 65536 is the current corresponds
    I use factory settings and didn't write any registers to DDC264

  • 0 in reply to Ildar Rakh
    TI__Prodigy 740 points

    Ildar,

    You will need to check the default settings for the range. Assuming 12.5pC, you can map the code to a corresponding charge.

    2^16 = 65536 codes, so 0-65535 discrete values in the range. If you read 30000 Decimal, the integrated charge is (30000/65535)*12.5pC = 5.72pC.

    Current is charge/time, so calculating current is as simple as taking the captured charge and dividing it over the integration time. I = Q(coulomb) / t(second)

    For more information, refer to Section 9.1 in the datasheet

    Regards,

    Shane

  • 0 in reply to Shane Aspenwall
    Prodigy 20 points

    Thank you so much, now it is clear for me

    I wanted to ask, if I didn't write any registers to DDC264 then according to the datasheet Table 3 my capacitors is 3pF ? 



    In my plan connect MCU directly to the input of DDC224 and generate via MCU 1mkA and check via calculation if I have the same value from DDC264, does it make sense?

  • 0 in reply to Ildar Rakh
    TI__Prodigy 740 points

    Ildar,

    I can't confirm the default setting, but the range being defaulted to 00 is likely. To test this, you can supply a voltage with a known series resistance to the input. Doing it this way, you can calculate the expected integrated charge on the capacitor after a conversion based on info in section 9.2.2.2.

    For example, If the default is 3pF, the max integrated charge is up to 12.5pC. You can set the CONV signal period to 800us for 400us/conversion.

    12.5pC / X = 400us, or 12.5pC/400us = 31.3nA is the highest input current you can resolve at the above capture rate for a given input.

    Regards,

    Shane