Noteworthy remarks on GPIOs usage and configuration

GPIOs configurations are set using SysConfig.

This section is aimed to highlight recommendation for the Debug Pins Configuration and the Pin Configuration After Closing A Driver.

Debug Pins Configuration

For designs where the debug pins (SWDIO and SWDCK) are left unused, developers should ensure these pins keep their default configuration - SWDIO pin should be set as input with pull up, SWDCK pin should be set as input with pull down. To do so, GPIO instances for the SWDIO and the SWDCK pins should be added in SysConfig as shown below:

../_images/SysConfig_swdio_swdck.png

Note

Alternatively, the field Do Not Configure can be set in both GPIOs instances.

For designs where the debug pins are repurposed as GPIO or used by drivers, developers should ensure the configuration set complies with the hardware design. In all the cases, floating inputs are discouraged. When left unused, the SWDIO pin should ideally be set as input with pull up, while the SWDCK pin should be set as input with pull down.

Warning

Incorrect configuration of the debug pins may lead to increased leakage current.

Pin Configuration After Closing A Driver

After closing a driver instance, the application is responsible to ensure the pin configuration is reverted to tri-state mode.

The listing below showcases reverting to tri-state the pin used by the ADC driver in the adcsinglechannel example available in the SDK. The same applies to all the driver-instances which are using one or several GPIO(s). In case a driver instance uses several GPIOs, each pin should be reverted to tri-state mode individually.

Listing 15. Revert the GPIO pin (CONFIG_GPIO_ADC_1_AIN) to tri state after closing the ADC instance that is using it
ADC_close(adc);
// The ADC driver instance "adc" does not use its pin anymore

// Set back the ADC pin in high impedance to reduce leakage current
GPIO_setConfig(CONFIG_GPIO_ADC_1_AIN, GPIO_CFG_NO_DIR);

Upon driver instance re-opening, the pins are reconfigured as required by the driver itself.

Warning

Failing to revert the tri-state mode configuration may lead to increased leakage current.