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LAUNCHXL-CC3235SF: Analog Input 2 Question

Gregory Lanier
Prodigy 230 points
Part Number: LAUNCHXL-CC3235SF
Other Parts Discussed in Thread: CC3235SF

Hello there,

Hopefully an easy question here. I am trying to use Analog input 2 on the CC3235SF eval board. To do this, I pulled up the adcsinglechannel example from the CC32xx sdk. I changed one of the ADC channels configured to use Analog input 2 (P58), and I am getting some weird reading that I was not expecting.

After checking the schematic for the eval board, I am assuming there is a resistor that is DSP? Specifically, I think it is resistor R123. However, I'm not sure how to find this on the eval board, as I can't open the altium files currently.

Am I correct in assuming this is the resistor I need to populate? If so, am I correct that I should use a 0 ohm resistor here?

Thanks,

Greg Slight smile

  • +1
    TI__Expert 6580 points

    Hello Greg,

    You are correct that it is disabled, as you can see from the schematic there are 2 resistors that are DNP (Do Not Populate).

     

    As such to use header Pin25 for ANALOG IN 2 you would have to populate R120 and R123. 

    It may be helpful to refer section "2.8.1 CC3235SF LaunchPad Drawing" of the CC3235 SimpleLink Wi-Fi® LaunchPad Development Kit Hardware (Lit# SWRU539) and the LAUNCHXL-CC3235SF quick start guide .  Also Note that we provide the Gerber files as well, which can be opened with any gerber tool. 

    Let me know if you have any other quations or concerns!

    BR,

    Jessica M. Torres

  • 0 in reply to Jessica M. Torres
    Prodigy 230 points

    Perfect. This is exactly the info I wanted to confirm.

    Can you clarify for me: I understand why R123 needs to be populated, but why do I need to populate R120 when similar resistors in the circuits for Analog inputs 1 and 3 are not populated? The resistors I am specifically referencing are R112, R113, and R121. Do I need to populate those as well if I intend to use 3 ADC channels, or is there another function of these resistors?

    Thanks Jessica,

    Greg