Poll groups

This sample is an event loop: one thread that waits on a queue of button events and a queue of accelerometer samples at once, each with its own message type, and handles whichever has something.

The wait returns the queue and leaves the message in it, so the loop receives it with the type that queue carries.

Run:: pbl samples samples/kernel/poll
Boards:: every board

Sources

src/main.c

#include <inttypes.h>

#include <pbl/kernel/delay.h>
#include <pbl/kernel/msgq.h>
#include <pbl/kernel/poll.h>
#include <pbl/kernel/thread.h>
#include <pbl/logging/logging.h>

struct button_event {
  uint8_t button;
  bool pressed;
};

struct accel_sample {
  int16_t x;
  int16_t y;
  int16_t z;
};

/* One queue per source, each with its own message type and depth. */
static PBL_MSGQ_DEFINE(s_buttons, sizeof(struct button_event), 4);
static PBL_MSGQ_DEFINE(s_accel, sizeof(struct accel_sample), 8);
static PBL_POLL_GROUP_DEFINE(s_events);

PBL_THREAD_STACK_DEFINE(s_source_stack, 1024);
static struct pbl_thread s_source;

static void prv_source(void *arg) {
  const struct button_event press = {.button = 1, .pressed = true};
  const struct button_event release = {.button = 1, .pressed = false};
  const struct accel_sample sample = {.x = 10, .y = -20, .z = 1000};

  pbl_msgq_put(&s_buttons, &press, PBL_FOREVER);
  pbl_sleep_ms(10);
  pbl_msgq_put(&s_accel, &sample, PBL_FOREVER);
  pbl_sleep_ms(10);
  pbl_msgq_put(&s_buttons, &release, PBL_FOREVER);
}

static void prv_handle(struct pbl_msgq *q) {
  /* The wait leaves the message in its queue. */
  if (q == &s_buttons) {
    struct button_event event;

    if (pbl_msgq_get(q, &event, PBL_NO_WAIT) == 0) {
      PBL_LOG_INFO("loop: button %u %s", event.button, event.pressed ? "pressed" : "released");
    }
  } else if (q == &s_accel) {
    struct accel_sample sample;

    if (pbl_msgq_get(q, &sample, PBL_NO_WAIT) == 0) {
      PBL_LOG_INFO("loop: accel %d %d %d", sample.x, sample.y, sample.z);
    }
  }
}

int main(void) {
  const struct pbl_thread_attr attr = {
    .name = "source",
    .entry = prv_source,
    .prio = CONFIG_KERNEL_MAIN_THREAD_PRIO - 1,
    .privileged = true,
    .stack = s_source_stack,
    .stack_size = sizeof(s_source_stack),
  };

  /* Queues join before the first wait, and for good. */
  pbl_poll_group_add(&s_events, &s_buttons);
  pbl_poll_group_add(&s_events, &s_accel);

  pbl_thread_create(&s_source, &attr);

  for (;;) {
    struct pbl_msgq *q = pbl_poll_group_wait(&s_events, PBL_MSEC(100));
    if (q == NULL) {
      PBL_LOG_INFO("loop: nothing for 100 ms");
      break;
    }

    prv_handle(q);
  }

  PBL_LOG_INFO("Sample done");

  return 0;
}

Output

loop: button 1 pressed
loop: accel 10 -20 1000
loop: button 1 released
loop: nothing for 100 ms
Sample done

PebbleOS

Poll groups

Sources

Output

Overview