AN: Capstone Dive Computer Example - Quantum Leaps

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Application Note: Capstone Dive Computer Example www.state-machine.com (4) QActive_subscribe((QActive *)me, B1_DOWN_SIG); QActive_subscribe((QActive *)me, B1_UP_SIG); QActive_subscribe((QActive *)me, B2_DOWN_SIG); QActive_subscribe((QActive *)me, B2_UP_SIG); . . . (5) return Q_TRAN(&Capstone_always); } /*..........................................................................*/ (6) QState Capstone_always(Capstone *me, QEvent const *e) { (7) switch (e->sig) { (8) case Q_ENTRY_SIG: { QTimeEvt_postEvery(&me->heartbeat, (QActive *)me, BSP_TICKS_PER_SEC/2); /* every 1/2 second */ QTimeEvt_postEvery(&me->dt_tts, (QActive *)me, BSP_TICKS_PER_SEC*2); /* every 2 seconds */ (9) return Q_HANDLED(); } case Q_EXIT_SIG: { QTimeEvt_disarm(&me->heartbeat); QTimeEvt_disarm(&me->dt_tts); return Q_HANDLED(); } case Q_INIT_SIG: { (10) return Q_TRAN(&Capstone_surfaced); } case B2_DOWN_SIG: { /* depth unit change request */ if (me->depth_units[0] == 'm') { me->depth_units[0] = 'f'; } else { me->depth_units[0] = 'm'; } Capstone_display_depth(me); return Q_HANDLED(); } case HEARTBEAT_SIG: { /* heartbeat arrives every 1/2 sec */ ADC_StandbyModeCmd(DISABLE); /* exit ADC standby mode */ ADC_ConversionCmd(ADC_Conversion_Start);/* start the conversion */ BSP_LED_on(15); /* trun on the ADC conversion LED */ if (me->heartbeat_led_sel) { BSP_LED_on(9); } else { BSP_LED_off(9); } me->heartbeat_led_sel = !me->heartbeat_led_sel; return Q_HANDLED(); } case DT_TTS_SIG: { /* alternate between dive-time/tts */ if (me->dt_tts_sel) { HD44780_StrShow(LCD_TTS_X, LCD_TTS_Y, "TTS"); HD44780_StrShow(LCD_TTS_X + 3, LCD_TTS_Y, ticks2min_sec(me->tts_in_ticks)); } else { HD44780_StrShow(LCD_TTS_X, LCD_TTS_Y, "Div"); HD44780_StrShow(LCD_TTS_X + 3, LCD_TTS_Y, ticks2min_sec(me->dive_time_in_ticks)); } me->dt_tts_sel = !me->dt_tts_sel; Copyright © Quantum Leaps, LLC. All Rights Reserved. 18 of 29
eturn Q_HANDLED(); } } (11) return Q_SUPER(&QHsm_top); } Application Note: Capstone Dive Computer Example www.state-machine.com Listing 3 Capstone state machine (file capstone.c). Boldface indicates the QP services (1) The Capstone_initial() function defines the actions executed by the top-most initial transition. (2) The top-most initial transition is the right place to initialize the hardware owned by the active object. Capstone object owns the LCD, so here it initializes the HD44780 device driver. (3) The top-most initial transition initializes the extended-state variables of the active object. (4) The active object subscribes to all interesting to it signals in the top-most initial transition. NOTE: New QP users often forget to subscribe to events and then the application appears unresponsive to certain events when you run it. (5) The initial state-handler must always return the Q_TRAN() macro, in which it must provide the pointer to the default initial state (&Capstone_surfaced in this case). (6) The state handler function with the signature QState Capstone_always(Capstone *me, QEvent const *e) corresponds to the state “always” in the Capstone state diagram (Figure 5). (7) Generally, every state-handler function is structured as a switch statement discriminating based on the event signal e->sig . (8) Case Q_ENTRY_SIG specifies the entry actions. (9) The Q_ENTRY_SIG case must return through the Q_HANLDED() macro provided by the QEP event processor. (10) The Q_INIT_SIG case represents the local initial transition in a composite state. The Q_INIT_SIG case must return through the Q_TRAN() macro, in which is specifies the default substate. (11) The final return Q_SUPER() statement specifies the nesting of the given state. If a state does not explicitly nest in any state, the QEP event processor provides the state handler QHsm_top, which is the ultimate root of state hierarchy. 2.7 Step 7: Initializing and Starting the Application Most of the system initialization and application startup can be written in a platform-independent way. In other words, you can use essentially the same main() function for the application with many QP ports. Typically, you start all your active objects from main(). The signature of the QActive_start() function forces you to make several important decisions about each active object upon startup. First, you need to decide the relative priorities of the active objects. Second, you need to decide the size of the event queues you pre-allocate for each active object. The correct size of the queue is actually related to the priority, as described in Chapter 9 of PSiCC2. Third, in some QF ports, you need to give each active object a separate stack, which also needs to be pre-allocated adequately. And finally, you need to decide the order in which you start your active objects. The order of starting active objects becomes important when you use an OS or RTOS in conjunction with the QP framework, and only when a spawned thread starts to run immediately, possibly preempting the main() thread from which you launch your application. This could cause problems, Copyright © Quantum Leaps, LLC. All Rights Reserved. 19 of 29
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