Extended sleep vs. UART

Dear Dialog,

I'm trying to put our application (DA14680-01, SDK 1.0.8.1050.1) to extended sleep. For this I took the extended_sleep demo app and ported it to our board (that has LEDs on LED pads, not GPIOs, so I put them on TIMER2/PWM). We're going to use UARTs, so I tried to print debug messages on UART2 from vTimerCallback() and put a call to hw_uart_reinit() in periph_init(). (For the output, I defined CONFIG_CUSTOM_PRINT and wrote a _write() function calling hw_uart_wrute_buffer(); I also tried to use ad_uart). I also added pm_set_wakeup_mode(true) to wait for XTAL16M to settle. The board has external 32.768kHz and 16MHz crystals.

However, the board behaviour changes, depending on how it was reset. If it was reset from JLink (by reboot_device.sh or by "monitor reset" from gdb), XTAL16M is running all the time (we checked with an oscilloscope), the LEDs stay on and UART output works.

But if it's reset either from firmware, or using the reset button, or by taking the battery out and putting it back in, XTAL16M stops and the LEDs go off during sleep; the LEDs still work when the board is awake. And if I try to use the UART after waking up, the CPU hangs and XTAL16M keeps running.

I'll appreciate if you can tell us how to use UARTs with extended sleep. The situation is a bit hard to debug, as I haven't found a way to attach the debugger without resetting the SoC.

Below are our periph_init() and write() functions.

Many thanks for your attention,
Vadim, MatchX.


静态孔隙periph_init (void)
{
/*
* Set-up Peripheral GPIOs
*/
hw_uart_reinit(HW_UART2, &uart_cfg);
hw_gpio_set_pin_function(HW_GPIO_PORT_4, HW_GPIO_PIN_5, HW_GPIO_MODE_OUTPUT,
HW_GPIO_FUNC_UART2_TX);
hw_gpio_set_pin_function(HW_GPIO_PORT_4, HW_GPIO_PIN_4, HW_GPIO_MODE_OUTPUT,
HW_GPIO_FUNC_UART2_RX);
/*
* Power up peripherals
*/
/*
* GPIO initializations
*/
/* Configure GPIO for LED output. */
timer2_config t2cfg = {
.pwm3_start = 0,
.pwm3_end = 0xffff,
.pwm4_start = 0,
.pwm4_end = 0xffff,
};
hw_timer2_init(&t2cfg);
hw_timer2_enable();
hw_led_set_led2_src(HW_LED_SRC2_PWM3);
hw_led_set_led3_src(HW_LED_SRC3_PWM4);
hw_led_enable_led2( ulLEDState & 1UL );
/* Configure GPIO for button. */
hw_gpio_set_pin_function(HW_GPIO_PORT_3, HW_GPIO_PIN_3, HW_GPIO_MODE_INPUT, HW_GPIO_FUNC_GPIO);
//printf("init\r\n");
}
int _write(int fd, char *ptr, int len)
{
hw_uart_write_buffer(HW_UART2, ptr, len);
return len;
}