ULP Advisor > Rule 4.1 Terminate unused GPIOs

ULP Advisor - Rule Table ULP 1.1 Ensure LPM usage ULP 2.1 Leverage timer module for delay loops ULP 3.1 Use ISRs instead of flag polling ULP 4.1 Terminate unused GPIOs ULP 5.1 Avoid processing-intensive operations: modulo, divide. ULP 5.2 Avoid processing-intensive operations: floating point ULP 5.3 Avoid processing-intensive operations: (s)printf() ULP 6.1 Avoid multiplication on devices without hardware multiplier ULP 6.2 Use MATHLIB for complex math operations ULP 6.3 Use Low Energy Accelerator (LEA) software library ULP 7.1 Use local instead of global variables where possible ULP 8.1 Use 'static' & 'const' modifiers for local variables ULP 9.1 Use pass by reference for large variables ULP 10.1 Minimize function calls from within ISRs ULP 11.1 Use lower bits for loop program control flow ULP 11.2 Use lower bits for port bit-banging ULP 12.1 Use DMA for large memcpy() calls ULP 12.1b Use DMA for potentially large memcpy() calls ULP 12.2 Use DMA for repetitive transfer ULP 13.1 Count down in loops ULP 14.1 Use unsigned variables for indexing ULP 15.1 Use bit-masks instead of bit-fields Let us know what you think! Feedback, suggestions & comments are welcome @ ULPAdvisorFeedback@list.ti.com

What it means

When an unused port pin is left undefined or non-terminated, the floating voltage or shoot-through current on the pin can increase the overall current consumption.

Risks, Severity

Considerable additional supply current due to undefined input voltages.

Why it is happening

This remark is issued when a port on the MSP430 device is not initialized/terminated:

Remedy

To remedy this ULP rule violation, each and every port on the MSP430 device needs to be initialized/terminated. Each port pin should have the following:

• Both of these code lines [output direction logic & level]:

  P1DIR = 0xFF;
  P1OUT = 0x00;
  

• Or this [select pin's secondary function]

  P1SEL = 0xBE;
  

• Or this if this register exists in the header file [2nd register to define pin's secondary function]:

  P1SEL2 = 0xEF;

Code Example

See the rest of the code examples for all MSP430 devices here!

More Resources

Want to squeeze a few more nanoAmps out of your application? Leverage the e2e (Engineer-to-Engineer) online community to get all of your ULP questions answered! Or, if you are an Ultra-Low Power pro, give back to the community with your expertise.

Go to MSP430's e2e online forum! 

If you are posting on the forums in relation to this rule, try using the tag "ULP_4.1"

Known Issues

Notice that ULP Advisor detects the number of ports & GPIO pins on the device basing strictly on the device number and does not have the knowledge on the actual package for the device. Therefore, it always assumes the largest package available to the device. In the event that a smaller package is actually used in the application, certain port pins might not be available on the device package. If this is the case, this remark can be safely ignored as these pins are internally terminated to ensure lowest power consumption and therefore the application is not required to configure/terminate these port pins.

For devices with Port 11 but no Port 12, ULP Advisor still checks for Port 12 initialization. This is a known bug and will be fixed in the upcoming release. At the moment, the workaround for this issue is to initialize Port 11 using Port F registers (16-bit wide).

For technical support please post your questions at http://e2e.ti.com. Please post only comments about the article Compiler/diagnostic messages/MSP430/10372 here.