Sleep current during k_sleep()

Question

In a nrf52840 project using Zephyr 3.0 following Zephyr drivers are used: 
 
 the modbus serial driver(RTU mode) which uses uart1 in interrupt mode 
 the lora-mac driver which uses spi1 
 serial logging on uart0 
 
 The application works fine but during inactivity periods the standby current is sometimes much too high: 520uA instead of ~10uA 
 I know that the uarts don't suspend automatically so immediately before k_sleep() I execute: 
 pm_device_action_run(uart0, PM_DEVICE_ACTION_SUSPEND); pm_device_action_run(uart1, PM_DEVICE_ACTION_SUSPEND); 
 Without success I also tried: 
 
 executing nrf_uart_errorsrc_get_and_clear() for both uarts before k_sleep(). 
 disable logging completely but as well without success. 
 "disable" all unneeded periphery in the device tree. 
 checked thread activity via the Zephyr Thread Analyzer but I could not find excessive activity. 
 executing pm_device_action_run () for spi1, gpio0, gpio1 , ... 
 modbus_disable() during sleep 
 ... 
 
 Do you have any hints how I could enclose or solve the problem? 
 Thx Matthias

mjm987 · Answer

Finally I came to following solution to solve my standby current problem: 
 1.) 
 Running ths function with argument true/false before/after k_sleep() : 
 void set_pm_mode_suspend(bool suspend) { const struct device *uart0 = device_get_binding(DT_LABEL(DT_NODELABEL(uart0))); const struct device *uart1 = device_get_binding(DT_LABEL(DT_NODELABEL(uart1))); const struct device *spi1 = device_get_binding(DT_LABEL(DT_NODELABEL(spi1))); enum pm_device_action action = suspend ? PM_DEVICE_ACTION_SUSPEND : PM_DEVICE_ACTION_RESUME; #ifdef CONFIG_LOG if (suspend) while (log_process(false)) ; // flush log buffer, otherwise it is lost #endif pm_device_action_run(uart1, action); // -1mA !! pm_device_action_run(uart0, action); // -3mA !! nrf_uart_errorsrc_get_and_clear((NRF_UART_Type *) DT_REG_ADDR(DT_NODELABEL(uart0))); nrf_uart_errorsrc_get_and_clear((NRF_UART_Type *) DT_REG_ADDR(DT_NODELABEL(uart1))); uart_irq_rx_disable(uart0); // no input (eg. shell) used on console port if (suspend) uart_irq_rx_disable(uart1); pm_device_action_run(spi1, action); } 
 Remark: with solution above, I could used normal console logging enabled using the default log buffering but mention that log messages from other tasks during set_pm_mode_suspend(true) will be lost. 
 
 2.) 
 Enabling a edge triggered GPIO button interrupt will caused additional 15uA current. Because of this level triggered interrupt is used by: 
 gpio_pin_interrupt_configure_dt(&button, GPIO_INT_LEVEL_ACTIVE); 
 Then disabling the interrupt in the interrupt handler by: 
 gpio_pin_interrupt_configure_dt(&button, GPIO_INT_DISABLE); 
 And reenable it later eg. by using a rtc timer or some application logic. 
 
 3.) 
 Before doing any current measurement, a power cycle is needed after flashing to disable the SWD interface! 
 Forther the connection to SWD and the console RxD/TxD has to be disconnected if the power supply is not sourced from the programmers VCC supply (eg. when using the PPK2 power supply).