3. Reset Functionality in DA1453x

The reset functionality POR (Power-On Reset) or HW reset (hardware) on P0_0 is multiplexed with SPI Slave MOSI and UART Tx. It is disabled when the P0_0 is used as a peripheral pin for 2-wire UART or SPI. See Figure 7 to see the behavior P0_0 during booting. After the booting, the reset functionality on the P0_0 is restored.

To configure the functionality of triggering a POR by a GPIO pin, follow the steps:

  1. Select a GPIO to be set as the POR source by programming POR_PIN_REG[POR_PIN_SELECT].

  2. Set up the input polarity of the GPIO that causes POR by programming POR_PIN_REG[POR_PIN_POLARITY].

  3. Configure the time for the POR to happen by programming POR_TIMER_REG[POR_TIME]. The default time is around three seconds.

Enable POR function

To be able to enable POR on a GPIO from the application software, the SDK has a function that can be used for this:

GPIO_EnablePorPin(GPIO_PORT port, GPIO_PIN pin, GPIO_POR_PIN_POLARITY polarity, uint8_t por_time);

port: GPIO port
pin: GPIO pin
polarity: GPIO port pin polarity. Active low = 0, Active high = 1.
por_time: Time for the Power-On Reset to happen. The time is calculated based on the following
equation: Time = por_time x 4096 x RC32 clock period

Example: To configure GPIO PORT 0 and PIN 7 (P0_7) as POR with a default POR time as 3 seconds and setting the polarity as active high, GPIO_EnablePorPin(GPIO_PORT_0, GPIO_PIN_7, 1 , 0x18). Calling this function, say after the system_init() will enable P0_7 to be a POR GPIO.

int main(void)
 {
 sleep_mode_t sleep_mode;
 // initialize retention mode
 init_retention_mode();
 //global initialise
 system_init();
 GPIO_EnablePorPin(GPIO_PORT_0, GPIO_PIN_7, 1 , 0x18);
 .
 .
 }

To trigger a POR via P0_7 at application code run time, connect a with a fly wire from P0_7 to J2[V3] of the motherboard for more than 3 seconds. Then the device will reset with the POR event.

../_images/DA1453x_Reset.svg

Figure 1 Reset on DA14531 DevkitP with DA14531 daughter board

../_images/da14535_Reset.svg

Figure 2 Reset on DA1453x DevkitP with DA14535 daughter board

Please be aware if a GPIO is used as a POR source, the dynamic current of the system increases due to the dynamic current consumed by the RC32k oscillator. This increase is estimated to be from 100 nA to 120 nA and it is also present during the sleep time period. POR from the RST pad does not add this dynamic current consumption. Note the POR functionality is not supported in the hibernation mode.

Note

For more details on the reset pin mapping on DA1453x check Appendix A Special considerations for Reset Functionality in the AN-B-075 for DA14531, AN-B-098 for DA14535 and R18AN0076EE0100 for DA14533.