client: Explain the exponential re-send delay

[tattlekey] / client / config.h

diff --git a/client/config.h b/client/config.h
index 7b89ba2cb583a3fc014cf93df211e2db7ec28793..8d23169c2d2701fd7a53627f0609b8aa5a29731e 100644 (file)
--- a/client/config.h
+++ b/client/config.h
@@ -1,14 +1,85 @@
+/* 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/>.
+ */
+

 #ifndef CONFIG_H
 #define CONFIG_H
 
 #include "lwip/arch.h"
 
 #ifndef CONFIG_H
 #define CONFIG_H
 
 #include "lwip/arch.h"
 

-extern char wifi_ssid[];
-extern char wifi_pass[];
+/* Wi-Fi credentials */
+extern const char config_wifi_ssid[];
+extern const char config_wifi_pass[];
+
+/* Network address of the server to contact */
+extern const char config_tattle_server_ip_address[];
+extern const u16_t config_tattle_port;
+
+/* For distinguishing reports from multiple tattlekey devices. */
+extern const u16_t config_this_tattler_identity;
+
+/* Which GPIO pin is the button connected to?
+ * The button should span this pin and ground, connecting this pin to ground
+ * when pressed.
+ * https://projects.raspberrypi.org/en/projects/introduction-to-the-pico/10
+ * recommends pins 18, 22, or 28. */
+extern const uint config_button_pin;
+
+/* Don't bother reporting each separate button press when it is pressed many
+ * times in short succession.  (We also use this to de-bounce. :) */
+extern const u32_t config_minimum_seconds_between_button_presses;
+
+/* Send each report multiple times. Re-sends are sent with exponential delay:
+ *   #1 sent immediately
+ *   #2 after 1 seconds
+ *   #3 after 2 seconds
+ *   #4 after 4 seconds
+ *   #5 after 8 seconds
+ *   ...
+ *   #11 after 8 minutes
+ *   #12 after 17 minutes
+ *   #13 after 34 minutes
+ *   #14 after 68 minutes
+ *   #15 after 2 hours
+ *   #16 after 4 hours
+ *   #17 after 9 hours
+ *   etc.
+ * This provides some robustness against network outages, automatically
+ * replaying the log periodically to be collected after connectivity
+ * is restored.
+ *
+ * Values above 17 are currently not recommended because the current
+ * wire format uses a 16-bit field for a duration in seconds, which wraps
+ * at 18 hours.
+ *   */
+extern const uint config_resend_count;

 
 

-extern u16_t tattle_port;
-extern char tattle_server_ip_address[];
+/* These control the size of the per-send-count press queues.
+When the button is pressed more than config_maximum_queue_size times
+within the resend interval, some presses will be reported fewer
+than config_resend_count times. This is usually fine because it's
+the old, longest-delyed, most-redundant reports that get dropped;
+fresh, timely reports of new button presses will not get anywhere near
+config_resend_count in a resend interval because the early resend interals
+are so short.  */
+extern const uint config_maximum_queue_size;

 
 

-extern u16_t this_tattler_identity;
+/* This is paranoia about unanticipated delays.  Setting this to zero
+would pobably be fine, but imposing a minimum queue size is an easy
+safety measure. */
+extern const uint config_minimum_queue_size;

 
 #endif
 
 #endif