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MSPM0L2117: Using LCD-connected pins as ADC inputs

Ibuki Endo
Prodigy 190 points

Part Number: MSPM0L2117

Hi, experts,

We are supporting a customer who plans to use the 48-pin MSPM0L2117 device.

Some of the pins that the customer intends to use as ADC inputs are connected to the onboard LCD panel on the LP-MSPM0L2117.

We understand that the MSPM0L2117 I/O pins can be multiplexed between LCD and other functions, and the customer will not enable the LCD controller. However, on the LaunchPad, the LCD glass remains physically connected to these pins.

We are concerned that the LCD panel may introduce additional capacitive loading on the ADC inputs and affect the ADC evaluation.

Could you clarify:

  • Can the LCD-connected pins be used for ADC evaluation with the LCD glass still connected?
  • Is there any expected impact on ADC performance due to the LCD panel connection?
  • Is there a jumper, resistor, trace, or other recommended method to isolate the LCD from the MCU pins?
  • If modification of the LaunchPad is required, what modification does TI recommend?
  • Is there another EVM that TI recommends for evaluating the ADC/peripheral functions of MSPM0L2117 without the onboard LCD?

Best regard,

Ibuki Endo

  • 0
    TI__Prodigy 250 points

    Hi ,

    Yes, the LCD connection could potentially affect ADC accuracy. Let me double-check the technical details and get back to you with a full explanation soon.

    Thanks

  • 0 in reply to Jasper Li
    TI__Prodigy 250 points

    Hi,

    Before providing a detailed response, I need to clarify a few technical details to ensure my answer is relevant to your application:
    1. Can you use the ADC pins that are not connected to the LCD (e.g., PA12, PA13, PA14, PA15, PA16, or PA18) for your evaluation?
    2. If you must use the pins connected to the LCD, please clarify the reason .

    Thanks

  • 0 in reply to Jasper Li
    Prodigy 190 points

    Hi expert,


    Thank you for your response.

    Regarding your questions:

    1. The customer plans to use the 48-pin MSPM0L2117 in their final product, and some of the pins they plan to use as ADC inputs are connected to the LCD on the LP-MSPM0L2117.

    2. For the evaluation, the customer would like to use the same pin assignment and software configuration as the production design. In addition, the other ADC-capable pins that are not connected to the LCD are already assigned to other functions.

    Therefore, rather than using alternative ADC pins such as PA12–PA18, we would like to evaluate the ADC using the same pins that will be used in the final product.

    The LCD will not be used in the customer's final product.

    Could you please advise whether the onboard LCD may affect ADC performance when using these pins? If so, is there a recommended way to electrically isolate the LCD from the relevant MCU pins on the LP-MSPM0L2117?

    Best regard,

    Ibuki Endo

  • 0 in reply to Ibuki Endo
    TI__Prodigy 250 points

    Hi,

    The LCD connection on the LaunchPad will inevitably impact ADC performance due to parasitic capacitance.
    Even without LCD functions active, the physical connection acts as a capacitive load. This requires more time for the ADC's internal capacitor to charge, which can cause voltage droop and sampling inaccuracies during measurement.
    To ensure an accurate evaluation of the chip's ADC performance, I recommend desoldering the LCD from the LaunchPad before conducting your tests. This will provide a baseline measurement free from hardware interference.
    Thanks

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