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doc: smf: Add Event Driven Example

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Add an example that demonstrates how the State Machine Framework
can be event driven. See Issue #48534

Signed-off-by: Sam Hurst <sbh1187@gmail.com>
This commit is contained in:
Sam Hurst 2022-08-25 12:41:49 -07:00 committed by Marti Bolivar
parent 6c7bf09222
commit 6f9e8f459d
1 changed files with 149 additions and 0 deletions
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149
doc/services/smf/index.rst
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@ -316,3 +316,152 @@ When designing hierarchical state machines, the following should be considered:
is called.
- The parent_run function only executes if the child_run function returns
without transitioning to another state, ie. calling smf_set_state.
Event Driven State Machine Example
==================================
Events are not explicitly part of the State Machine Framework but an event driven
state machine can be implemented using Zephyr :ref:`events`.
.. graphviz::
:caption: Event driven state machine diagram
digraph smf_flat {
node [style=rounded];
init [shape = point];
STATE_S0 [shape = box];
STATE_S1 [shape = box];
init -> STATE_S0;
STATE_S0 -> STATE_S1 [label = "BTN EVENT"];
STATE_S1 -> STATE_S0 [label = "BTN EVENT"];
}
Code::
#include <zephyr/kernel.h>
#include <zephyr/zephyr.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/smf.h>
#define SW0_NODE DT_ALIAS(sw0)
/* List of events */
#define EVENT_BTN_PRESS BIT(0)
static const struct gpio_dt_spec button =
GPIO_DT_SPEC_GET_OR(SW0_NODE, gpios, {0});
static struct gpio_callback button_cb_data;
/* Forward declaration of state table */
static const struct smf_state demo_states[];
/* List of demo states */
enum demo_state { S0, S1 };
/* User defined object */
struct s_object {
/* This must be first */
struct smf_ctx ctx;
/* Events */
struct k_event smf_event;
int32_t events;
/* Other state specific data add here */
} s_obj;
/* State S0 */
static void s0_entry(void *o)
{
printk("STATE0\n");
}
static void s0_run(void *o)
{
struct s_object *s = (struct s_object *)o;
/* Change states on Button Press Event */
if (s->events & EVENT_BTN_PRESS) {
smf_set_state(SMF_CTX(&s_obj), &demo_states[S1]);
}
}
/* State S1 */
static void s1_entry(void *o)
{
printk("STATE1\n");
}
static void s1_run(void *o)
{
struct s_object *s = (struct s_object *)o;
/* Change states on Button Press Event */
if (s->events & EVENT_BTN_PRESS) {
smf_set_state(SMF_CTX(&s_obj), &demo_states[S0]);
}
}
/* Populate state table */
static const struct smf_state demo_states[] = {
[S0] = SMF_CREATE_STATE(s0_entry, s0_run, NULL),
[S1] = SMF_CREATE_STATE(s1_entry, s1_run, NULL),
};
void button_pressed(const struct device *dev,
struct gpio_callback *cb, uint32_t pins)
{
/* Generate Button Press Event */
k_event_post(&s_obj.smf_event, EVENT_BTN_PRESS);
}
void main(void)
{
int ret;
if (!device_is_ready(button.port)) {
printk("Error: button device %s is not ready\n",
button.port->name);
return;
}
ret = gpio_pin_configure_dt(&button, GPIO_INPUT);
if (ret != 0) {
printk("Error %d: failed to configure %s pin %d\n",
ret, button.port->name, button.pin);
return;
}
ret = gpio_pin_interrupt_configure_dt(&button,
GPIO_INT_EDGE_TO_ACTIVE);
if (ret != 0) {
printk("Error %d: failed to configure interrupt on %s pin %d\n",
ret, button.port->name, button.pin);
return;
}
gpio_init_callback(&button_cb_data, button_pressed, BIT(button.pin));
gpio_add_callback(button.port, &button_cb_data);
/* Initialize the event */
k_event_init(&s_obj.smf_event);
/* Set initial state */
smf_set_initial(SMF_CTX(&s_obj), &demo_states[S0]);
/* Run the state machine */
while(1) {
/* Block until an event is detected */
s_obj.events = k_event_wait(&s_obj.smf_event,
EVENT_BTN_PRESS, true, K_FOREVER);
/* State machine terminates if a non-zero value is returned */
ret = smf_run_state(SMF_CTX(&s_obj));
if (ret) {
/* handle return code and terminate state machine */
break;
}
}
}