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CC2340R5: How to set the IO port to input high impedance

QIngtian Yang
Prodigy 70 points
Part Number: CC2340R5

Tool/software:

In the latest Errata for the CC2340R5 SimpleLinkTm Wireless MCU Device Revision B, it is mentioned that setting a GPIO to high-impedance state can cause a high-level voltage fluctuation.

We wish to verify the impact of this issue. First, we want to set the GPIO to high-impedance state. Could you please confirm if the following settings will configure the GPIO as high-impedance? If not, how should I set it up? (Using the IAR development environment and SDK 8.10)

// Possible GPIO configurations
#define IOC_INPUT_TRISTATE                                                                                   \
  (IOC_IOC12_IOCURR_CUR_2MA | IOC_IOC12_IOSTR_AUTO | IOC_IOC12_PULLCTL_PULL_DIS | IOC_IOC12_SLEWRED_REDUCED | IOC_IOC12_HYSTEN_DIS | IOC_IOC12_EDGEDET_EDGE_DIS | IOC_NO_WAKE_UP | 
   IOC_IOC12_IOMODE_NORMAL | IOC_IOC12_INPEN_EN)
   
  // Get the register address.
  u32Reg = IOC_ADDR(u32PinId);

  // Configure the port and configuration.
  HWREG(u32Reg) = IOC_INPUT_TRISTATE | u32PortId;

  • 0
    TI__Expert 6450 points

    Hello,

    I think you may be misinterpreting the errata item. The errata issue is related to the way open-drain outputs such as for I2C are implemented.

    This errata item can be evaluated for yourself by setting an output as I2C which uses open drain. In open drain there are two states, output low and high-impedance. When the output is high-impedance the bus is driven high by the pull-up resistor. It's during the transition from low to open-drain that you would encounter the issue. An easy way to do this would be to use one of the I2C examples and send some data. You could evaluate on a LaunchPad or your own hardware. You should note that the event happens for less than 2ns so you'll need a very low capacitance oscilloscope probe to see anything.

    Jake