FreeRTOS with libuarte: incompatibility between app_timer and app_timer_freertos?

Question

Hello, I intend to use libuarte under FreeRTOS together with the SoftDevice (SDK 17.1.0). An app_timer is used for the RX timeout. I think there might be an incompatibility problem between app_timer and app_timer_freertos. My application initializes the libuarte as follows: NRF_LIBUARTE_ASYNC_DEFINE( xLibUarteCOM0, 0, 1, NRF_LIBUARTE_PERIPHERAL_NOT_USED, NRF_LIBUARTE_PERIPHERAL_NOT_USED, 255, 3 ); xErrCode = nrf_libuarte_async_init( ( nrf_libuarte_async_t * )&xLibUarteCOM0, &nrf_libuarte_async_config, pvUartEvtHandler, ( void * )pxLibUarte ); The macro NRF_LIBUARTE_ASYNC_DEFINE creates xLibUarteCOM0 as follows: static const nrf_libuarte_async_t xLibUarteCOM0 = { .p_rx_pool = &xLibUarteCOM0_rx_pool, .p_rx_queue = &xLibUarteCOM0_rxdata_queue, .p_rtc = 0, .p_timer = 0, .p_app_timer = &xLibUarteCOM0_app_timer, .p_app_timer_ctrl_blk = &xLibUarteCOM0_app_timer_ctrl_blk, .p_libuarte = &xLibUarteCOM0_libuarte, .p_ctrl_blk = &xLibUarteCOM0ctrl_blk, .rx_buf_size = 255, }; with p_app_timer_t being a pointer to (a pointer to) a variable of type app_timer_t: static const app_timer_id_t xLibUarteCOM0_app_timer = &xLibUarteCOM0_app_timer_data; typedef struct { nrf_sortlist_item_t list_item; /**< Token used by sortlist. */ uint64_t end_val; /**< RTC counter value when timer expires or @ref APP_TIMER_IDLE_VAL. */ uint32_t repeat_period; /**< Repeat period (0 if single shot mode). */ app_timer_timeout_handler_t handler; /**< User handler. */ void * p_context; /**< User context. */ NRF_LOG_INSTANCE_PTR_DECLARE(p_log) /**< Pointer to instance of the logger object (Conditionally compiled). */ } app_timer_t; The structure is then initialized by the macro as: static app_timer_t xLibUarteCOM0_app_timer_data = { .end_val = 0xFFFFFFFFFFFFFFFFULL, }; In the FreeRTOS version of app_timer_create() called from nrf_libuarte_async_init(), xLibUarteCOM0_app_timer_data gets overlaid by a different structure. It is recasted to app_timer_info_t: app_timer_info_t * pinfo = (app_timer_info_t*)(*p_timer_id); /**@brief This structure keeps information about osTimer.*/ typedef struct { void * argument; TimerHandle_t osHandle; app_timer_timeout_handler_t func; /** * This member is to make sure that timer function is only called if timer is running. * FreeRTOS may have timer running even after stop function is called, * because it processes commands in Timer task and stopping function only puts command into the queue. */ bool active; bool single_shot; }app_timer_info_t; Without further initialization of the structure, app_timer_create() then checks the value of pinfo->active and fails with NRF_ERROR_INVALID_STATE if true. The pinfo->active variable, however, is part of the pre-initialized 64-bit end_val and has the value 0xff which evaluates to true (!= 0). Hence, the initialization fails. A possible work-around (although not very clean) is to initialize end_val with 0: app_timer_t *p_xLibUarteCOM0_app_timer_data = *xLibUarteCOM0.p_app_timer; p_xLibUarteCOM0_app_timer_data->end_val = 0x0ULL; Does my analysis sound corrected or is there a another issue somewhere? Thanks, Norbert

Susheel Nuguru · Accepted Answer

OK, then i will not try to push you to use other instances of RTC then, in that case let us go to your initial efforts and look at the issue. 
 
 I think the main issue here is that the helper macros in the NRF_LIBUARTE_ASYNC_DEFINE has not been designed to work with the freertos. 
 so probably you can initialize p_app_timer pointing zero initialized structure of app_timer_info_t instead as a clean workaround.