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client: Explain the exponential re-send delay
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1 /* tattlekey: A one-key UDP keyboard
2 * Copyright (C) 2023 Scott Worley <scottworley@scottworley.com>
3 *
4 * This program is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <https://www.gnu.org/licenses/>.
16 */
17
18 #ifndef CONFIG_H
19 #define CONFIG_H
20
21 #include "lwip/arch.h"
22
23 /* Wi-Fi credentials */
24 extern const char config_wifi_ssid[];
25 extern const char config_wifi_pass[];
26
27 /* Network address of the server to contact */
28 extern const char config_tattle_server_ip_address[];
29 extern const u16_t config_tattle_port;
30
31 /* For distinguishing reports from multiple tattlekey devices. */
32 extern const u16_t config_this_tattler_identity;
33
34 /* Which GPIO pin is the button connected to?
35 * The button should span this pin and ground, connecting this pin to ground
36 * when pressed.
37 * https://projects.raspberrypi.org/en/projects/introduction-to-the-pico/10
38 * recommends pins 18, 22, or 28. */
39 extern const uint config_button_pin;
40
41 /* Don't bother reporting each separate button press when it is pressed many
42 * times in short succession. (We also use this to de-bounce. :) */
43 extern const u32_t config_minimum_seconds_between_button_presses;
44
45 /* Send each report multiple times. Re-sends are sent with exponential delay:
46 * #1 sent immediately
47 * #2 after 1 seconds
48 * #3 after 2 seconds
49 * #4 after 4 seconds
50 * #5 after 8 seconds
51 * ...
52 * #11 after 8 minutes
53 * #12 after 17 minutes
54 * #13 after 34 minutes
55 * #14 after 68 minutes
56 * #15 after 2 hours
57 * #16 after 4 hours
58 * #17 after 9 hours
59 * etc.
60 * This provides some robustness against network outages, automatically
61 * replaying the log periodically to be collected after connectivity
62 * is restored.
63 *
64 * Values above 17 are currently not recommended because the current
65 * wire format uses a 16-bit field for a duration in seconds, which wraps
66 * at 18 hours.
67 * */
68 extern const uint config_resend_count;
69
70 /* These control the size of the per-send-count press queues.
71 When the button is pressed more than config_maximum_queue_size times
72 within the resend interval, some presses will be reported fewer
73 than config_resend_count times. This is usually fine because it's
74 the old, longest-delyed, most-redundant reports that get dropped;
75 fresh, timely reports of new button presses will not get anywhere near
76 config_resend_count in a resend interval because the early resend interals
77 are so short. */
78 extern const uint config_maximum_queue_size;
79
80 /* This is paranoia about unanticipated delays. Setting this to zero
81 would pobably be fine, but imposing a minimum queue size is an easy
82 safety measure. */
83 extern const uint config_minimum_queue_size;
84
85 #endif