client: Explain the exponential re-send delay

[tattlekey] / client / tattlekey.c

diff --git a/client/tattlekey.c b/client/tattlekey.c
index 3a1f7b7b67212de7437b593f1b4f8c1512ad305a..9d255856b74a41cc93dc8d2a5a927dff6571e4ba 100644 (file)
--- a/client/tattlekey.c
+++ b/client/tattlekey.c
@@ -1,25 +1,132 @@
+/* tattlekey: A one-key UDP keyboard
+ * Copyright (C) 2023  Scott Worley <scottworley@scottworley.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
 #include "pico/cyw43_arch.h"
 #include "pico/stdlib.h"
+#include "pico/util/pheap.h"
 #include "pico/util/queue.h"
 
 #include "blink.h"
 #include "button.h"
 #include "config.h"
 #include "net.h"
+#include "press.h"
+
+enum event_type { NEW_BUTTON_PRESS, RESEND_TIME };
+typedef struct {
+  enum event_type type;
+  union {
+    struct {
+      uint32_t timestamp;
+    } buttonpress;
+  };
+} event_t;
 
 queue_t queue;
 
+uint32_t time_s() { return time_us_64() / 1000000ul; }
+
+/* Often we don't bother checking for failure (full queue) because
+ *   1. The best thing to do in this unfortunate situation is to blithely
+ *      continue, dropping some events; continuing is better than stopping.
+ *   2. Neither interrupt context nor queue-processing context can block
+ *      until space is available, or even sit around & blink the LED to
+ *      signal a problem.
+ * (We also get a bit of type safety by taking event_t* rather than void*.) */
+static void queue_try_add_ignoring_errors(queue_t *q, event_t *e) {
+  queue_try_add(q, e);
+}
+
 static void button_pressed() {
   /* This runs in interrupt context; don't linger.  */
   static uint64_t last_button_press_time = 0;
-  uint64_t now = time_us_64();
-  uint64_t time_since_last_press = now - last_button_press_time;
-  if (time_since_last_press > minimum_microseconds_between_button_presses) {
+  uint32_t now = time_s();
+  uint32_t time_since_last_press = now - last_button_press_time;
+  if (time_since_last_press >= config_minimum_seconds_between_button_presses) {
     last_button_press_time = now;
-    char zero = '\0';
-    /* We don't check for failure (full queue) here because there's not much to
-     * be done about it. */
-    queue_try_add(&queue, &zero);
+    event_t e;
+    e.type = NEW_BUTTON_PRESS;
+    e.buttonpress.timestamp = now;
+    queue_try_add_ignoring_errors(&queue, &e);
+  }
+}
+
+static void time_to_send(uint _) {
+  /* This runs in interrupt context; don't linger.  */
+  event_t e;
+  e.type = RESEND_TIME;
+  queue_try_add_ignoring_errors(&queue, &e);
+}
+
+void set_resend_alarm(int alarm, uint32_t now, uint32_t next_act_time) {
+  uint32_t sleep_duration = next_act_time - now;
+  if (hardware_alarm_set_target(alarm,
+                                make_timeout_time_ms(sleep_duration * 1000)))
+    signal_error_by_blinking();
+}
+
+void service_sleeps(int alarm, press_pile_t *pp) {
+  hardware_alarm_cancel(alarm);
+
+  while (1) {
+    uint32_t now = time_s();
+    int32_t act_time = next_scheduled_send(pp);
+    if (act_time == -1)
+      return;
+    if (act_time > now) {
+      set_resend_alarm(alarm, now, act_time);
+      return;
+    }
+    press_t press;
+    if (!get_press_due_for_resend(pp, now, &press))
+      signal_error_by_blinking();
+    uint32_t ago = now - press.timestamp;
+    send_report_packet(press.seq, ago);
+    press.send_count++;
+    if (press.send_count < config_resend_count) {
+      add_press(pp, &press);
+    }
+  }
+}
+
+void service_queue() {
+  int alarm = hardware_alarm_claim_unused(true);
+  if (alarm == -1)
+    signal_error_by_blinking();
+  hardware_alarm_set_callback(alarm, time_to_send);
+
+  press_pile_t *pp = create_press_pile();
+  u16_t seq = 0;
+  while (1) {
+    service_sleeps(alarm, pp);
+
+    event_t e;
+    queue_remove_blocking(&queue, &e);
+    switch (e.type) {
+    case NEW_BUTTON_PRESS: {
+      add_press(pp, &(press_t){e.buttonpress.timestamp, seq++, 0});
+    } break;
+    case RESEND_TIME: {
+      /* OK, we're awake. Cool. Thanks! (We actually do the sends in the
+       * service_sleeps() call at the top of the loop.)  */
+    } break;
+    default:
+      signal_error_by_blinking();
+    }
   }
 }
 
@@ -29,20 +136,14 @@ int main() {
     signal_error_by_blinking();
   cyw43_arch_enable_sta_mode();
   signal(3, 100);
-  if (cyw43_arch_wifi_connect_timeout_ms(wifi_ssid, wifi_pass,
+  if (cyw43_arch_wifi_connect_timeout_ms(config_wifi_ssid, config_wifi_pass,
                                          CYW43_AUTH_WPA2_AES_PSK, 90000))
     signal_error_by_blinking();
   signal(2, 300);
 
-  queue_init(&queue, 1, 99);
+  queue_init(&queue, sizeof(event_t), 99);
 
   begin_listening_for_button_press(button_pressed);
 
-  u16_t seq = 0;
-  while (1) {
-    char _;
-    queue_remove_blocking(&queue, &_);
-    send_report(seq++, 0);
-    signal(2, 100);
-  }
+  service_queue();
 }