From 1160d15a6b32391178728d2df04d09fbcce791e1 Mon Sep 17 00:00:00 2001
From: Jonathan Ma <jonathanjma03@gmail.com>
Date: Tue, 24 Sep 2024 17:42:37 -0400
Subject: [PATCH 01/12] update lora parameters

---
 src/constants.hpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/constants.hpp b/src/constants.hpp
index 7a512ce..e10a51d 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -13,9 +13,9 @@ namespace constants {
         constexpr int radio_rst_pin = 5;
         constexpr int radio_busy_pin = 16;
 
-        constexpr float freq = 433.0;
-        constexpr float bw = 125.0;
-        constexpr int sf = 12;
+        constexpr float freq = 431.5;
+        constexpr float bw = 62.5;
+        constexpr int sf = 10;
         constexpr int cr = 5;
         constexpr int sw = 18;
         constexpr int pwr = 20;

From 5b6d2dbf70a9781a0f00e3786322174af701ef1e Mon Sep 17 00:00:00 2001
From: Jonathan Ma <jonathanjma03@gmail.com>
Date: Thu, 10 Oct 2024 17:17:12 -0400
Subject: [PATCH 02/12] Use one second slot lengths

---
 src/constants.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/constants.hpp b/src/constants.hpp
index e10a51d..adf60e0 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -32,7 +32,7 @@ namespace constants {
         constexpr uint32_t command_wait_period = 30 * constants::time::one_second;
         constexpr uint32_t callsign_interval = 10 * constants::time::one_minute;
 
-        constexpr uint32_t transmit_slot_length = 2 * constants::time::one_second;
+        constexpr uint32_t transmit_slot_length = 1 * constants::time::one_second;
 
     } // namespace radio
     namespace imu {

From 853e8a4f6ca8be8d6cfafe0d8ac5f145821fe1a8 Mon Sep 17 00:00:00 2001
From: Jonathan Ma <jonathanjma03@gmail.com>
Date: Sat, 2 Nov 2024 18:02:47 -0400
Subject: [PATCH 03/12] Add alive signal, fix gps is valid

---
 src/ControlTasks/RadioControlTask.cpp | 16 ++++++++++++++--
 src/Modes/radio_mode_type.enum        |  1 +
 src/Monitors/GPSMonitor.cpp           |  4 ++++
 src/constants.hpp                     |  6 ++++--
 src/sfr.cpp                           |  7 +++++--
 src/sfr.hpp                           |  6 ++++--
 6 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index 07418e0..60f9a48 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -154,6 +154,17 @@ void RadioControlTask::execute()
 #endif
         init();
         if (sfr::radio::initialized) {
+            sfr::radio::mode = radio_mode_type::aliveSignal;
+        }
+        break;
+    }
+    case radio_mode_type::aliveSignal: {
+#ifdef VERBOSE
+        Serial.println(F("Radio: Alive Signal State"));
+#endif
+        normalReportDownlink();
+        sfr::radio::alive_signal_dlinks++;
+        if (sfr::radio::alive_signal_dlinks == constants::radio::max_alive_signal_dlinks) {
             sfr::radio::mode = radio_mode_type::downlink;
             sfr::radio::listen_period_start = millis();
             downlinkSettings();
@@ -243,8 +254,9 @@ bool RadioControlTask::normalReportDownlink()
     uint16_t alt = sfr::gps::altitude / 10;
 
     uint8_t flags = 0;
-    flags |= constants::radio::id << 6;
-    flags |= sfr::gps::valid_msg << 5;                           // gps valid
+    flags |= constants::radio::id << 7;
+    flags |= sfr::gps::valid_location << 6;
+    flags |= sfr::gps::valid_altitude << 5;                      // gps valid
     flags |= sfr::imu::initialized << 4;                         // imu valid
     flags |= sfr::gps::on << 3;                                  // boot mode flag
     flags |= (sfr::radio::mode == radio_mode_type::listen) << 2; // listen flag
diff --git a/src/Modes/radio_mode_type.enum b/src/Modes/radio_mode_type.enum
index 6a5d100..0d42e92 100644
--- a/src/Modes/radio_mode_type.enum
+++ b/src/Modes/radio_mode_type.enum
@@ -4,6 +4,7 @@
 enum class radio_mode_type : unsigned char
 {
     init = 0,
+    aliveSignal,
     downlink,
     listen
 };
diff --git a/src/Monitors/GPSMonitor.cpp b/src/Monitors/GPSMonitor.cpp
index b2113cf..e76a3e0 100644
--- a/src/Monitors/GPSMonitor.cpp
+++ b/src/Monitors/GPSMonitor.cpp
@@ -33,6 +33,7 @@ void GPSMonitor::execute()
         gps.encode(ss.read());
         serial_reads++;
     }
+    // for testing only
     // while (*gpsStream) {
     //     gps.encode(*gpsStream++);
     // }
@@ -50,6 +51,9 @@ void GPSMonitor::execute()
         sfr::gps::utc_time = gps.time.value();
     }
 
+    sfr::gps::valid_location = gps.location.isValid();
+    sfr::gps::valid_altitude = gps.altitude.isValid();
+
 #ifdef VERBOSE
     Serial.print(F("Chars="));
     Serial.print(gps.charsProcessed());
diff --git a/src/constants.hpp b/src/constants.hpp
index adf60e0..6ef9a94 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -22,6 +22,8 @@ namespace constants {
         constexpr int pl = 8;
         constexpr int gn = 0;
 
+        constexpr uint8_t max_alive_signal_dlinks = 3;
+
 #ifdef CHIPSAT_ID
         constexpr uint8_t id = CHIPSAT_ID;
 #else
@@ -32,7 +34,7 @@ namespace constants {
         constexpr uint32_t command_wait_period = 30 * constants::time::one_second;
         constexpr uint32_t callsign_interval = 10 * constants::time::one_minute;
 
-        constexpr uint32_t transmit_slot_length = 1 * constants::time::one_second;
+        constexpr uint32_t transmit_slot_length = constants::time::one_second / 5; // 200 ms
 
     } // namespace radio
     namespace imu {
@@ -55,7 +57,7 @@ namespace constants {
         constexpr int reset_pin = 7;
         constexpr int buffer_size = 11;
 
-        constexpr uint32_t boot_time = constants::time::one_second * 30;
+        constexpr uint32_t boot_time = 30 * constants::time::one_second;
     } // namespace gps
     namespace opcodes {
         constexpr uint8_t no_op = 0x00;
diff --git a/src/sfr.cpp b/src/sfr.cpp
index 735c711..03d41fd 100644
--- a/src/sfr.cpp
+++ b/src/sfr.cpp
@@ -17,7 +17,8 @@ namespace sfr {
     } // namespace temperature
     namespace gps {
         float utc_time, latitude, longitude, altitude;
-        bool valid_msg = false;
+        bool valid_location = false;
+        bool valid_altitude = false;
         bool on = false;
 
         uint32_t boot_time = 0;
@@ -27,8 +28,10 @@ namespace sfr {
         bool initialized = false;
         radio_mode_type mode = radio_mode_type::init;
         uint8_t start_progress = 0;
+        uint8_t alive_signal_dlinks = 0;
 
-        uint32_t downlink_window_length = 10 * constants::time::one_second;
+        // try to keep window 10x the slot length
+        uint32_t downlink_window_length = 2 * constants::time::one_second;
         uint32_t downlink_window_start;
         uint32_t listen_period_start;
         uint32_t command_wait_start;
diff --git a/src/sfr.hpp b/src/sfr.hpp
index 90d6910..dcb584b 100644
--- a/src/sfr.hpp
+++ b/src/sfr.hpp
@@ -26,8 +26,9 @@ namespace sfr {
     } // namespace temperature
     namespace radio {
         extern bool initialized;
-        extern uint8_t start_progress;
         extern radio_mode_type mode;
+        extern uint8_t start_progress;
+        extern uint8_t alive_signal_dlinks;
 
         extern uint32_t downlink_window_length;
         extern uint32_t downlink_window_start;
@@ -49,7 +50,8 @@ namespace sfr {
         extern float longitude;
         extern float altitude;
 
-        extern bool valid_msg;
+        extern bool valid_location = false;
+        extern bool valid_altitude = false;
         extern bool on;
 
         extern uint32_t boot_time;

From 128e38ca7f580c8e42e76e2ce0e792f70fa228eb Mon Sep 17 00:00:00 2001
From: Cameron Goddard <camerongoddard@me.com>
Date: Sat, 2 Nov 2024 18:16:35 -0400
Subject: [PATCH 04/12] update LoRa params

---
 src/constants.hpp | 4 ++--
 src/sfr.hpp       | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/constants.hpp b/src/constants.hpp
index 6ef9a94..704b32d 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -13,8 +13,8 @@ namespace constants {
         constexpr int radio_rst_pin = 5;
         constexpr int radio_busy_pin = 16;
 
-        constexpr float freq = 431.5;
-        constexpr float bw = 62.5;
+        constexpr float freq = 435;
+        constexpr float bw = 250;
         constexpr int sf = 10;
         constexpr int cr = 5;
         constexpr int sw = 18;
diff --git a/src/sfr.hpp b/src/sfr.hpp
index dcb584b..bef501f 100644
--- a/src/sfr.hpp
+++ b/src/sfr.hpp
@@ -50,8 +50,8 @@ namespace sfr {
         extern float longitude;
         extern float altitude;
 
-        extern bool valid_location = false;
-        extern bool valid_altitude = false;
+        extern bool valid_location;
+        extern bool valid_altitude;
         extern bool on;
 
         extern uint32_t boot_time;

From e8a8ac27b6ea558dc8cc29b7bae0475026b07a8d Mon Sep 17 00:00:00 2001
From: Cameron Goddard <camerongoddard@me.com>
Date: Sat, 2 Nov 2024 18:33:22 -0400
Subject: [PATCH 05/12] add LED indicators

---
 src/ControlTasks/RadioControlTask.cpp | 2 ++
 src/MainControlLoop.cpp               | 4 ++++
 src/constants.hpp                     | 6 ++++++
 src/main.cpp                          | 4 ++++
 4 files changed, 16 insertions(+)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index 60f9a48..fc972cf 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -63,9 +63,11 @@ void RadioControlTask::init()
 
 bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
 {
+    // digitalWrite(constants::led::led_pin, HIGH);
     uint32_t start = millis();
     code = radio.transmit(packet, size);
     uint32_t time = millis() - start;
+    // digitalWrite(constants::led::led_pin, LOW);
     Serial.print(F("Time to transmit (ms): "));
     Serial.println(time);
 
diff --git a/src/MainControlLoop.cpp b/src/MainControlLoop.cpp
index cf6b15a..1f94f26 100644
--- a/src/MainControlLoop.cpp
+++ b/src/MainControlLoop.cpp
@@ -71,6 +71,10 @@ void MainControlLoop::execute()
     gps_monitor.execute();
     radio_control_task.execute();
 
+    if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
+        digitalWrite(constants::led::led_pin, LOW);
+    }
+
     wdt_reset();
 
 #ifdef VERBOSE
diff --git a/src/constants.hpp b/src/constants.hpp
index 704b32d..5a147fc 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -64,6 +64,12 @@ namespace constants {
         constexpr uint8_t change_downlink_window = 0x11;
     } // namespace opcodes
 
+    namespace led {
+        constexpr int led_pin = 9;
+        constexpr uint32_t led_on_time = 5 * constants::time::one_second;
+    }
+    
+
 }; // namespace constants
 
 #endif
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index c655380..a311d78 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -11,6 +11,10 @@ void setup()
     Serial.begin(9600);
 #endif
 
+    // sets ChipSat LED high for debugging
+    pinMode(constants::led::led_pin, OUTPUT);
+    digitalWrite(constants::led::led_pin, HIGH);
+
     // cuts off power to GPS
     pinMode(constants::gps::reset_pin, OUTPUT);
     digitalWrite(constants::gps::reset_pin, HIGH);

From 2e8a07c4cf40dc27b563846afd569ccdca05e0b5 Mon Sep 17 00:00:00 2001
From: Cameron Goddard <camerongoddard@me.com>
Date: Sat, 16 Nov 2024 22:43:18 -0500
Subject: [PATCH 06/12] fix packet format, update transmit window and slot
 sizes

---
 src/ControlTasks/RadioControlTask.cpp | 12 ++++++------
 src/constants.hpp                     |  4 ++--
 src/sfr.cpp                           |  2 +-
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index fc972cf..56892d3 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -256,12 +256,12 @@ bool RadioControlTask::normalReportDownlink()
     uint16_t alt = sfr::gps::altitude / 10;
 
     uint8_t flags = 0;
-    flags |= constants::radio::id << 7;
-    flags |= sfr::gps::valid_location << 6;
-    flags |= sfr::gps::valid_altitude << 5;                      // gps valid
-    flags |= sfr::imu::initialized << 4;                         // imu valid
-    flags |= sfr::gps::on << 3;                                  // boot mode flag
-    flags |= (sfr::radio::mode == radio_mode_type::listen) << 2; // listen flag
+    flags |= constants::radio::id << 6;
+    flags |= sfr::gps::valid_location << 5;
+    flags |= sfr::gps::valid_altitude << 4;                      // gps valid
+    flags |= sfr::imu::initialized << 3;                         // imu valid
+    flags |= sfr::gps::on << 2;                                  // boot mode flag
+    flags |= (sfr::radio::mode == radio_mode_type::listen) << 1; // listen flag
 
     uint8_t dlink[] = {
         (uint8_t)lat, (uint8_t)(lat >> 8),
diff --git a/src/constants.hpp b/src/constants.hpp
index 5a147fc..f1f5f85 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -14,7 +14,7 @@ namespace constants {
         constexpr int radio_busy_pin = 16;
 
         constexpr float freq = 435;
-        constexpr float bw = 250;
+        constexpr float bw = 62.5;
         constexpr int sf = 10;
         constexpr int cr = 5;
         constexpr int sw = 18;
@@ -34,7 +34,7 @@ namespace constants {
         constexpr uint32_t command_wait_period = 30 * constants::time::one_second;
         constexpr uint32_t callsign_interval = 10 * constants::time::one_minute;
 
-        constexpr uint32_t transmit_slot_length = constants::time::one_second / 5; // 200 ms
+        constexpr uint32_t transmit_slot_length = 700; // ms
 
     } // namespace radio
     namespace imu {
diff --git a/src/sfr.cpp b/src/sfr.cpp
index 03d41fd..5981811 100644
--- a/src/sfr.cpp
+++ b/src/sfr.cpp
@@ -31,7 +31,7 @@ namespace sfr {
         uint8_t alive_signal_dlinks = 0;
 
         // try to keep window 10x the slot length
-        uint32_t downlink_window_length = 2 * constants::time::one_second;
+        uint32_t downlink_window_length = 3500;
         uint32_t downlink_window_start;
         uint32_t listen_period_start;
         uint32_t command_wait_start;

From b2173f153ec61cc9cf3f89b8f5f98b956094498a Mon Sep 17 00:00:00 2001
From: Cameron Goddard <camerongoddard@me.com>
Date: Sat, 16 Nov 2024 22:43:59 -0500
Subject: [PATCH 07/12] format

---
 src/constants.hpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/constants.hpp b/src/constants.hpp
index f1f5f85..05d9ece 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -67,8 +67,7 @@ namespace constants {
     namespace led {
         constexpr int led_pin = 9;
         constexpr uint32_t led_on_time = 5 * constants::time::one_second;
-    }
-    
+    } // namespace led
 
 }; // namespace constants
 

From de9d26e4397ad5e2db1fb7860837ed26a2faa4a6 Mon Sep 17 00:00:00 2001
From: Jonathan Ma <jonathanjma03@gmail.com>
Date: Sun, 17 Nov 2024 22:00:34 -0500
Subject: [PATCH 08/12] Fix led blink on transmit

---
 src/ControlTasks/RadioControlTask.cpp | 12 ++++++++++--
 src/Monitors/GPSMonitor.hpp           |  8 ++++----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index 56892d3..2ffc6f4 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -63,13 +63,21 @@ void RadioControlTask::init()
 
 bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
 {
-    // digitalWrite(constants::led::led_pin, HIGH);
+    if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
+        digitalWrite(constants::led::led_pin, HIGH);
+    }
+
     uint32_t start = millis();
     code = radio.transmit(packet, size);
     uint32_t time = millis() - start;
-    // digitalWrite(constants::led::led_pin, LOW);
+
+    if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
+        digitalWrite(constants::led::led_pin, LOW);
+    }
+#ifdef VERBOSE
     Serial.print(F("Time to transmit (ms): "));
     Serial.println(time);
+#endif
 
     if (code == RADIOLIB_ERR_NONE) {
         // the packet was successfully transmitted
diff --git a/src/Monitors/GPSMonitor.hpp b/src/Monitors/GPSMonitor.hpp
index 0453dc0..b53eb82 100644
--- a/src/Monitors/GPSMonitor.hpp
+++ b/src/Monitors/GPSMonitor.hpp
@@ -31,10 +31,10 @@ class GPSMonitor
      */
     void init();
 
-    // TODO: Test edge cases for lat, lon, alt
-    const char *gpsStream = "$GPGGA,045104.000,3014.1985,N,09749.2873,W,1,09,1.2,211.6,M,-22.5,M,,0000*62\r\n"
-                            "$GPGGA,045201.000,3014.3864,N,09748.9411,W,1,10,1.2,200.8,M,-22.5,M,,0000*6C\r\n"
-                            "$GPGG@,045252.000,3014.4273,S,09749.0628,W,1,09,1.3,206.9,M,-22.5,M,,0000*6F\r\n";
+    // for edge case testing only
+    // const char *gpsStream = "$GPGGA,045104.000,3014.1985,N,09749.2873,W,1,09,1.2,211.6,M,-22.5,M,,0000*62\r\n"
+    //                         "$GPGGA,045201.000,3014.3864,N,09748.9411,W,1,10,1.2,200.8,M,-22.5,M,,0000*6C\r\n"
+    //                         "$GPGG@,045252.000,3014.4273,S,09749.0628,W,1,09,1.3,206.9,M,-22.5,M,,0000*6F\r\n";
 };
 
 #endif
\ No newline at end of file

From 1571de706ad5cf138ec583e62f768e7b9f489d7e Mon Sep 17 00:00:00 2001
From: Jonathan Ma <jonathanjma03@gmail.com>
Date: Tue, 19 Nov 2024 21:49:52 -0500
Subject: [PATCH 09/12] Change listen period to 30 minutes, update comments

---
 src/ControlTasks/RadioControlTask.cpp | 17 ++++-------------
 src/MainControlLoop.cpp               |  1 +
 src/Monitors/GPSMonitor.cpp           |  6 ++----
 src/Monitors/GPSMonitor.hpp           |  5 -----
 src/constants.hpp                     |  2 +-
 src/main.cpp                          |  1 +
 src/sfr.cpp                           |  5 +++--
 7 files changed, 12 insertions(+), 25 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index 2ffc6f4..859f218 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -63,6 +63,7 @@ void RadioControlTask::init()
 
 bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
 {
+    // blink LED during transmit
     if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
         digitalWrite(constants::led::led_pin, HIGH);
     }
@@ -114,23 +115,13 @@ bool RadioControlTask::receive()
         // packet was successfully received
         Serial.println(F("success!"));
 
-        // print the data of the packet
         Serial.print(F("[SX1278] Data:\t\t\t"));
-
-        // print the RSSI (Received Signal Strength Indicator)
-        // of the last received packet
         Serial.print(F("[SX1278] RSSI:\t\t\t"));
         Serial.print(radio.getRSSI());
         Serial.println(F(" dBm"));
-
-        // print the SNR (Signal-to-Noise Ratio)
-        // of the last received packet
         Serial.print(F("[SX1278] SNR:\t\t\t"));
         Serial.print(radio.getSNR());
         Serial.println(F(" dB"));
-
-        // print frequency error
-        // of the last received packet
         Serial.print(F("[SX1278] Frequency error:\t"));
         Serial.print(radio.getFrequencyError());
         Serial.println(F(" Hz"));
@@ -264,9 +255,9 @@ bool RadioControlTask::normalReportDownlink()
     uint16_t alt = sfr::gps::altitude / 10;
 
     uint8_t flags = 0;
-    flags |= constants::radio::id << 6;
-    flags |= sfr::gps::valid_location << 5;
-    flags |= sfr::gps::valid_altitude << 4;                      // gps valid
+    flags |= constants::radio::id << 6;                          // chipsat ID #
+    flags |= sfr::gps::valid_location << 5;                      // gps position valid
+    flags |= sfr::gps::valid_altitude << 4;                      // gps altiude valid
     flags |= sfr::imu::initialized << 3;                         // imu valid
     flags |= sfr::gps::on << 2;                                  // boot mode flag
     flags |= (sfr::radio::mode == radio_mode_type::listen) << 1; // listen flag
diff --git a/src/MainControlLoop.cpp b/src/MainControlLoop.cpp
index 1f94f26..459aa4a 100644
--- a/src/MainControlLoop.cpp
+++ b/src/MainControlLoop.cpp
@@ -71,6 +71,7 @@ void MainControlLoop::execute()
     gps_monitor.execute();
     radio_control_task.execute();
 
+    // turn off LED 5 seconds after boot
     if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
         digitalWrite(constants::led::led_pin, LOW);
     }
diff --git a/src/Monitors/GPSMonitor.cpp b/src/Monitors/GPSMonitor.cpp
index e76a3e0..bf75605 100644
--- a/src/Monitors/GPSMonitor.cpp
+++ b/src/Monitors/GPSMonitor.cpp
@@ -19,6 +19,7 @@ void GPSMonitor::init()
 
 void GPSMonitor::execute()
 {
+    // turn on GPS after boot mode is over (30 seconds)
     if (!sfr::gps::on) {
         if (millis() - sfr::gps::boot_time > constants::gps::boot_time) {
             init();
@@ -33,11 +34,8 @@ void GPSMonitor::execute()
         gps.encode(ss.read());
         serial_reads++;
     }
-    // for testing only
-    // while (*gpsStream) {
-    //     gps.encode(*gpsStream++);
-    // }
 
+    // read GPS values if they are valid
     if (gps.location.isUpdated() && gps.location.isValid()) {
         sfr::gps::latitude = gps.location.lat();
         sfr::gps::longitude = gps.location.lng();
diff --git a/src/Monitors/GPSMonitor.hpp b/src/Monitors/GPSMonitor.hpp
index b53eb82..2e81340 100644
--- a/src/Monitors/GPSMonitor.hpp
+++ b/src/Monitors/GPSMonitor.hpp
@@ -30,11 +30,6 @@ class GPSMonitor
      * Begins the software serial instance and configures the GPS receiver
      */
     void init();
-
-    // for edge case testing only
-    // const char *gpsStream = "$GPGGA,045104.000,3014.1985,N,09749.2873,W,1,09,1.2,211.6,M,-22.5,M,,0000*62\r\n"
-    //                         "$GPGGA,045201.000,3014.3864,N,09748.9411,W,1,10,1.2,200.8,M,-22.5,M,,0000*6C\r\n"
-    //                         "$GPGG@,045252.000,3014.4273,S,09749.0628,W,1,09,1.3,206.9,M,-22.5,M,,0000*6F\r\n";
 };
 
 #endif
\ No newline at end of file
diff --git a/src/constants.hpp b/src/constants.hpp
index 05d9ece..f7b8eab 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -30,7 +30,7 @@ namespace constants {
         constexpr uint8_t id = 0;
 #endif
 
-        constexpr uint32_t listen_period = 30 * constants::time::one_second;
+        constexpr uint32_t listen_period = 30 * constants::time::one_minute;
         constexpr uint32_t command_wait_period = 30 * constants::time::one_second;
         constexpr uint32_t callsign_interval = 10 * constants::time::one_minute;
 
diff --git a/src/main.cpp b/src/main.cpp
index a311d78..1a749a7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -5,6 +5,7 @@ MainControlLoop mcl;
 
 void setup()
 {
+    // configure watchdog timer
     wdt_disable();
     wdt_enable(WDTO_8S);
 #ifdef VERBOSE
diff --git a/src/sfr.cpp b/src/sfr.cpp
index 5981811..51d0e9e 100644
--- a/src/sfr.cpp
+++ b/src/sfr.cpp
@@ -30,8 +30,9 @@ namespace sfr {
         uint8_t start_progress = 0;
         uint8_t alive_signal_dlinks = 0;
 
-        // try to keep window 10x the slot length
-        uint32_t downlink_window_length = 3500;
+        // This must be a multiple of constants::radio::transmit_slot_length
+        // Ideally window should be 10x the slot length
+        uint32_t downlink_window_length = 3500; // ms
         uint32_t downlink_window_start;
         uint32_t listen_period_start;
         uint32_t command_wait_start;

From d7947990e215c31fe7518fd2e37f95f3e17acdd9 Mon Sep 17 00:00:00 2001
From: Jonathan Ma <jonathanjma03@gmail.com>
Date: Sat, 14 Dec 2024 15:20:43 -0500
Subject: [PATCH 10/12] fully initialize radio in first cycle

---
 src/ControlTasks/RadioControlTask.cpp | 37 ++++++++++++---------------
 src/MainControlLoop.cpp               |  5 +++-
 src/main.cpp                          |  4 +--
 3 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index 859f218..02b1645 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -7,10 +7,9 @@ RadioControlTask::RadioControlTask()
 void RadioControlTask::init()
 {
     if (!sfr::radio::initialized) {
-        switch (sfr::radio::start_progress) {
-        case 0:
+        if (sfr::radio::start_progress == 0) {
 #ifdef VERBOSE
-            Serial.print(F("Radio: Initializing ... "));
+            Serial.println(F("Radio: Initializing ... "));
 #endif
             // initialize SX1278 with default settings
             code = radio.begin(constants::radio::freq, constants::radio::bw, constants::radio::sf, constants::radio::cr,
@@ -23,10 +22,11 @@ void RadioControlTask::init()
                 Serial.println(code);
 #endif
             }
-            break;
-        case 1:
+        }
+
+        if (sfr::radio::start_progress == 1) {
 #ifdef VERBOSE
-            Serial.print(F("Radio: Setting CRC parameter ... "));
+            Serial.println(F("Radio: Setting CRC parameter ... "));
 #endif
             // set CRC parameter to true so it matches the CRC parameter on the TinyGS side
             code = radio.setCRC(true);
@@ -38,25 +38,22 @@ void RadioControlTask::init()
                 Serial.println(code);
 #endif
             }
-            break;
-        case 2:
+
+            if (sfr::radio::start_progress == 2) {
 #ifdef VERBOSE
-            Serial.print(F("Radio: Setting forceLDRO parameter ... "));
+                Serial.println(F("Radio: Setting forceLDRO parameter ... "));
 #endif
-            // set forceLDRO parameter to true so it matches the forceLDRO parameter on the TinyGS side
-            code = radio.forceLDRO(true);
-            if (code == RADIOLIB_ERR_NONE) {
-                sfr::radio::start_progress++;
-            } else {
+                // set forceLDRO parameter to true so it matches the forceLDRO parameter on the TinyGS side
+                code = radio.forceLDRO(true);
+                if (code == RADIOLIB_ERR_NONE) {
+                    sfr::radio::initialized = true;
+                } else {
 #ifdef VERBOSE
-                Serial.print(F("failed, code "));
-                Serial.println(code);
+                    Serial.print(F("failed, code "));
+                    Serial.println(code);
 #endif
+                }
             }
-            break;
-        case 3: // completed initialization
-            sfr::radio::initialized = true;
-            break;
         }
     }
 }
diff --git a/src/MainControlLoop.cpp b/src/MainControlLoop.cpp
index 459aa4a..fc27207 100644
--- a/src/MainControlLoop.cpp
+++ b/src/MainControlLoop.cpp
@@ -61,9 +61,12 @@ void MainControlLoop::execute()
     Serial.print(F("GPS Altitude (m): "));
     Serial.println(sfr::gps::altitude);
 
-    Serial.print("Downlink Slot: ");
+    Serial.print(F("Downlink Slot: "));
     Serial.println(sfr::radio::downlink_slot);
 
+    Serial.print(F("Alive Time: "));
+    Serial.println(millis() - sfr::gps::boot_time);
+
 #endif
 
     temp_monitor.execute();
diff --git a/src/main.cpp b/src/main.cpp
index 1a749a7..a1ebf0c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -12,6 +12,8 @@ void setup()
     Serial.begin(9600);
 #endif
 
+    sfr::gps::boot_time = millis();
+
     // sets ChipSat LED high for debugging
     pinMode(constants::led::led_pin, OUTPUT);
     digitalWrite(constants::led::led_pin, HIGH);
@@ -24,8 +26,6 @@ void setup()
     pinMode(constants::gps::tx_pin, OUTPUT);
     digitalWrite(constants::gps::tx_pin, LOW);
 
-    sfr::gps::boot_time = millis();
-
     // seed random number gen with noise from unconnected analog pin
     randomSeed(analogRead(A0));
 }

From 742b267a3c9ac35be5ab52068f48949e212446df Mon Sep 17 00:00:00 2001
From: Cameron Goddard <camerongoddard@me.com>
Date: Wed, 18 Dec 2024 15:45:13 -0500
Subject: [PATCH 11/12] changes from code review

---
 src/ControlTasks/RadioControlTask.cpp | 6 +++++-
 src/ControlTasks/RadioControlTask.hpp | 4 ++--
 src/Monitors/TempMonitor.cpp          | 3 +--
 src/constants.hpp                     | 8 ++++----
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index 02b1645..a96e470 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -65,9 +65,13 @@ bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
         digitalWrite(constants::led::led_pin, HIGH);
     }
 
+#ifdef VERBOSE
     uint32_t start = millis();
+#endif
     code = radio.transmit(packet, size);
+#ifdef VERBOSE
     uint32_t time = millis() - start;
+#endif
 
     if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
         digitalWrite(constants::led::led_pin, LOW);
@@ -234,7 +238,7 @@ bool RadioControlTask::executeDownlink()
     if (millis() - sfr::radio::last_callsign_time < constants::radio::callsign_interval) {
         return normalReportDownlink();
     } else {
-        uint8_t dlink[] = {'K', 'D', '2', 'W', 'T', 'Q'};
+        uint8_t dlink[] = {'K', 'C', '3', 'V', 'A', 'T', 'K', 'D', '2', 'W', 'T', 'Q', 'K', 'E', '2', 'A', 'T', 'R'};
         sfr::radio::last_callsign_time = millis();
 #ifdef VERBOSE
         Serial.println(F("Callsign Report"));
diff --git a/src/ControlTasks/RadioControlTask.hpp b/src/ControlTasks/RadioControlTask.hpp
index 6f9ed03..be0be74 100644
--- a/src/ControlTasks/RadioControlTask.hpp
+++ b/src/ControlTasks/RadioControlTask.hpp
@@ -26,12 +26,12 @@ class RadioControlTask
     void downlinkSettings();
 
     /**
-     * @brief Wrapper around RadioLib's transmit() to provide metadata (TODO: Redundant?)
+     * @brief Wrapper around RadioLib's transmit() to provide metadata
      */
     bool transmit(uint8_t *packet, uint8_t size);
 
     /**
-     * @brief Attempts to receive a 3 byte command (TODO: Redundant?)
+     * @brief Attempts to receive a 3 byte command
      */
     bool receive();
 
diff --git a/src/Monitors/TempMonitor.cpp b/src/Monitors/TempMonitor.cpp
index 59144b2..2df3e1d 100644
--- a/src/Monitors/TempMonitor.cpp
+++ b/src/Monitors/TempMonitor.cpp
@@ -13,11 +13,10 @@ void TempMonitor::execute()
     // Select no hold master
     Wire.write(0xF3);
     Wire.endTransmission();
-    delay(300); // TODO: Look at this delay
+    delay(300); // TODO: Look at this delay (for real)
 
     // Request 2 bytes of data
     Wire.requestFrom(constants::temperature::i2c_address, 2);
-    // TODO: Delay here?
 
     if (Wire.available() == 2) {
         data[0] = Wire.read();
diff --git a/src/constants.hpp b/src/constants.hpp
index f7b8eab..7730d44 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -12,8 +12,8 @@ namespace constants {
         constexpr int radio_di0_pin = 2;
         constexpr int radio_rst_pin = 5;
         constexpr int radio_busy_pin = 16;
-
-        constexpr float freq = 435;
+        // TODO: Document units
+        constexpr float freq = 437.4;
         constexpr float bw = 62.5;
         constexpr int sf = 10;
         constexpr int cr = 5;
@@ -35,7 +35,7 @@ namespace constants {
         constexpr uint32_t callsign_interval = 10 * constants::time::one_minute;
 
         constexpr uint32_t transmit_slot_length = 700; // ms
-
+    // TODO: Verify sensor data on alive signal
     } // namespace radio
     namespace imu {
         constexpr int gyro_min = -245; // default gyro range is +/- 245 dps
@@ -57,7 +57,7 @@ namespace constants {
         constexpr int reset_pin = 7;
         constexpr int buffer_size = 11;
 
-        constexpr uint32_t boot_time = 30 * constants::time::one_second;
+        constexpr uint32_t boot_time = 10 * constants::time::one_second;
     } // namespace gps
     namespace opcodes {
         constexpr uint8_t no_op = 0x00;

From 4242e18862f5780b51903f9aa003c00bc6386c81 Mon Sep 17 00:00:00 2001
From: Cameron Goddard <camerongoddard@me.com>
Date: Tue, 24 Dec 2024 18:12:13 -0500
Subject: [PATCH 12/12] clean up

---
 src/ControlTasks/RadioControlTask.cpp | 36 +++++++++++++--------------
 src/ControlTasks/RadioControlTask.hpp |  2 +-
 src/MainControlLoop.cpp               |  2 +-
 src/Monitors/GPSMonitor.cpp           |  6 ++---
 src/Monitors/GPSMonitor.hpp           |  2 +-
 src/Monitors/IMUMonitor.cpp           |  9 +++----
 src/constants.hpp                     | 30 +++++++++++-----------
 src/main.cpp                          | 10 ++++----
 src/sfr.cpp                           |  9 ++-----
 src/sfr.hpp                           |  6 ++---
 10 files changed, 52 insertions(+), 60 deletions(-)

diff --git a/src/ControlTasks/RadioControlTask.cpp b/src/ControlTasks/RadioControlTask.cpp
index a96e470..e4bc1b2 100644
--- a/src/ControlTasks/RadioControlTask.cpp
+++ b/src/ControlTasks/RadioControlTask.cpp
@@ -11,7 +11,7 @@ void RadioControlTask::init()
 #ifdef VERBOSE
             Serial.println(F("Radio: Initializing ... "));
 #endif
-            // initialize SX1278 with default settings
+            // Initialize SX1278 with default settings
             code = radio.begin(constants::radio::freq, constants::radio::bw, constants::radio::sf, constants::radio::cr,
                                constants::radio::sw, constants::radio::pwr, constants::radio::pl, constants::radio::gn);
             if (code == RADIOLIB_ERR_NONE) {
@@ -28,7 +28,7 @@ void RadioControlTask::init()
 #ifdef VERBOSE
             Serial.println(F("Radio: Setting CRC parameter ... "));
 #endif
-            // set CRC parameter to true so it matches the CRC parameter on the TinyGS side
+            // Set CRC parameter to true so it matches the CRC parameter on the TinyGS side
             code = radio.setCRC(true);
             if (code == RADIOLIB_ERR_NONE) {
                 sfr::radio::start_progress++;
@@ -43,7 +43,7 @@ void RadioControlTask::init()
 #ifdef VERBOSE
                 Serial.println(F("Radio: Setting forceLDRO parameter ... "));
 #endif
-                // set forceLDRO parameter to true so it matches the forceLDRO parameter on the TinyGS side
+                // Set forceLDRO parameter to true so it matches the forceLDRO parameter on the TinyGS side
                 code = radio.forceLDRO(true);
                 if (code == RADIOLIB_ERR_NONE) {
                     sfr::radio::initialized = true;
@@ -60,7 +60,7 @@ void RadioControlTask::init()
 
 bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
 {
-    // blink LED during transmit
+    // Blink LED during transmit
     if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
         digitalWrite(constants::led::led_pin, HIGH);
     }
@@ -82,7 +82,7 @@ bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
 #endif
 
     if (code == RADIOLIB_ERR_NONE) {
-        // the packet was successfully transmitted
+        // The packet was successfully transmitted
 #ifdef VERBOSE
         Serial.println(F("success!"));
         Serial.print(F("[SX1278] Datarate:\t"));
@@ -93,10 +93,10 @@ bool RadioControlTask::transmit(uint8_t *packet, uint8_t size)
     } else {
 #ifdef VERBOSE
         if (code == RADIOLIB_ERR_TX_TIMEOUT) {
-            // timeout occurred while transmitting packet
+            // Timeout occurred while transmitting packet
             Serial.println(F("timeout!"));
         } else {
-            // some other error occurred
+            // Some other error occurred
             Serial.print(F("failed, code "));
             Serial.println(code);
         }
@@ -131,13 +131,13 @@ bool RadioControlTask::receive()
     } else {
 #ifdef VERBOSE
         if (code == RADIOLIB_ERR_RX_TIMEOUT) {
-            // timeout occurred while waiting for a packet
+            // Timeout occurred while waiting for a packet
             Serial.println(F("timeout!"));
         } else if (code == RADIOLIB_ERR_CRC_MISMATCH) {
-            // packet was received, but is malformed
+            // Packet was received, but is malformed
             Serial.println(F("CRC error!"));
         } else {
-            // some other error occurred
+            // Some other error occurred
             Serial.print(F("failed, code "));
             Serial.println(code);
         }
@@ -148,7 +148,7 @@ bool RadioControlTask::receive()
 
 void RadioControlTask::execute()
 {
-    // implements the state machine described in: https://github.com/Alpha-CubeSat/oop-chipsat-code/wiki
+    // Implement the state machine described in https://github.com/Alpha-CubeSat/oop-chipsat-code/wiki
     switch (sfr::radio::mode) {
     case radio_mode_type::init: {
 #ifdef VERBOSE
@@ -177,24 +177,24 @@ void RadioControlTask::execute()
 #ifdef VERBOSE
         Serial.println(F("Radio: Downlink State"));
 #endif
-        // downlink when slot reached
+        // Downlink when slot reached
         if (!sfr::radio::downlinked_in_slot && millis() - sfr::radio::downlink_window_start >= constants::radio::transmit_slot_length * sfr::radio::downlink_slot) {
             executeDownlink();
             sfr::radio::downlinked_in_slot = true;
         }
 
-        // go into listen mode if listen period reached
+        // Go into listen mode if listen period reached
         if (millis() - sfr::radio::listen_period_start >= constants::radio::listen_period) {
             sfr::radio::mode = radio_mode_type::listen;
 
 #ifdef VERBOSE
             Serial.println(F("Radio: Listen Flag Downlink"));
 #endif
-            // downlink with listen flag = true
+            // Downlink with listen flag = true
             normalReportDownlink();
             sfr::radio::command_wait_start = millis();
         }
-        // reset window and choose slot for next downlink
+        // Reset window and choose slot for next downlink
         else if (millis() - sfr::radio::downlink_window_start >= sfr::radio::downlink_window_length) {
             downlinkSettings();
         }
@@ -204,7 +204,7 @@ void RadioControlTask::execute()
 #ifdef VERBOSE
         Serial.println(F("Radio: Listen State"));
 #endif
-        // built in timeout is 100 LoRa symbols
+        // Built in timeout is 100 LoRa symbols
         bool receive_success = receive();
         if (receive_success) {
             processUplink();
@@ -250,7 +250,7 @@ bool RadioControlTask::executeDownlink()
 
 bool RadioControlTask::normalReportDownlink()
 {
-    // see https://github.com/Alpha-CubeSat/oop-chipsat-code/wiki/2.-Telemetry for more info
+    // See https://github.com/Alpha-CubeSat/oop-chipsat-code/wiki/2.-Telemetry for more info
     uint16_t lat = sfr::gps::latitude * 100;
     uint16_t lon = sfr::gps::longitude * 100;
     uint16_t alt = sfr::gps::altitude / 10;
@@ -300,7 +300,7 @@ uint8_t RadioControlTask::map_range(float value, int min_val, int max_val)
 
 void RadioControlTask::processUplink()
 {
-    // see https://github.com/Alpha-CubeSat/oop-chipsat-code/wiki/3.-Commands for more info
+    // See https://github.com/Alpha-CubeSat/oop-chipsat-code/wiki/3.-Commands for more info
     switch (received[0]) {
     case constants::opcodes::no_op: // No-Op
 #ifdef VERBOSE
diff --git a/src/ControlTasks/RadioControlTask.hpp b/src/ControlTasks/RadioControlTask.hpp
index be0be74..8daeb09 100644
--- a/src/ControlTasks/RadioControlTask.hpp
+++ b/src/ControlTasks/RadioControlTask.hpp
@@ -21,7 +21,7 @@ class RadioControlTask
     void init();
 
     /**
-     * Resets the transmit window start time and picks a new slot
+     * @brief Resets the transmit window start time and picks a new slot
      */
     void downlinkSettings();
 
diff --git a/src/MainControlLoop.cpp b/src/MainControlLoop.cpp
index fc27207..ccf6445 100644
--- a/src/MainControlLoop.cpp
+++ b/src/MainControlLoop.cpp
@@ -74,7 +74,7 @@ void MainControlLoop::execute()
     gps_monitor.execute();
     radio_control_task.execute();
 
-    // turn off LED 5 seconds after boot
+    // Turn off LED 5 seconds after boot
     if (millis() - sfr::gps::boot_time > constants::led::led_on_time) {
         digitalWrite(constants::led::led_pin, LOW);
     }
diff --git a/src/Monitors/GPSMonitor.cpp b/src/Monitors/GPSMonitor.cpp
index bf75605..1241a7f 100644
--- a/src/Monitors/GPSMonitor.cpp
+++ b/src/Monitors/GPSMonitor.cpp
@@ -9,7 +9,7 @@ void GPSMonitor::init()
     digitalWrite(constants::gps::reset_pin, LOW);
     sfr::gps::on = true;
 
-    // writes NMEA output message type to SRAM and Flash
+    // Writes NMEA output message type to SRAM and Flash
     uint8_t SetNMEA[] = {
         0xA0, 0xA1, 0x00, 0x03, 0x09, 0x01, 0x01, 0x09, 0x0D, 0x0A};
 
@@ -19,7 +19,7 @@ void GPSMonitor::init()
 
 void GPSMonitor::execute()
 {
-    // turn on GPS after boot mode is over (30 seconds)
+    // Turn on GPS after boot mode is over (10 seconds)
     if (!sfr::gps::on) {
         if (millis() - sfr::gps::boot_time > constants::gps::boot_time) {
             init();
@@ -35,7 +35,7 @@ void GPSMonitor::execute()
         serial_reads++;
     }
 
-    // read GPS values if they are valid
+    // Read GPS values if they are valid
     if (gps.location.isUpdated() && gps.location.isValid()) {
         sfr::gps::latitude = gps.location.lat();
         sfr::gps::longitude = gps.location.lng();
diff --git a/src/Monitors/GPSMonitor.hpp b/src/Monitors/GPSMonitor.hpp
index 2e81340..7cd8abd 100644
--- a/src/Monitors/GPSMonitor.hpp
+++ b/src/Monitors/GPSMonitor.hpp
@@ -27,7 +27,7 @@ class GPSMonitor
     SoftwareSerial ss = SoftwareSerial(constants::gps::rx_pin, constants::gps::tx_pin);
 
     /**
-     * Begins the software serial instance and configures the GPS receiver
+     * @brief Begins the software serial instance and configures the GPS receiver
      */
     void init();
 };
diff --git a/src/Monitors/IMUMonitor.cpp b/src/Monitors/IMUMonitor.cpp
index 1d8b422..f6dabe4 100644
--- a/src/Monitors/IMUMonitor.cpp
+++ b/src/Monitors/IMUMonitor.cpp
@@ -18,7 +18,6 @@ void IMUMonitor::execute()
         } else {
             sfr::imu::initialized = true;
         }
-
     } else {
         capture_imu_values();
     }
@@ -26,25 +25,25 @@ void IMUMonitor::execute()
 
 void IMUMonitor::capture_imu_values()
 {
-    // check if the gyroscope, accelerometer, or magnetometer has new data available
+    // Check if the gyroscope, accelerometer, or magnetometer has new data available
     if (IMU.gyroscopeAvailable()) {
         IMU.readGyroscope(
             sfr::imu::gyro_x,
             sfr::imu::gyro_y,
-            sfr::imu::gyro_z); // data is in degrees/s
+            sfr::imu::gyro_z); // Data is in degrees/s
     }
 
     if (IMU.accelerationAvailable()) {
         IMU.readAcceleration(
             sfr::imu::acc_x,
             sfr::imu::acc_y,
-            sfr::imu::acc_z); // data is in m/s^2
+            sfr::imu::acc_z); // Data is in m/s^2
     }
 
     if (IMU.magneticFieldAvailable()) {
         IMU.readMagneticField(
             sfr::imu::mag_x,
             sfr::imu::mag_y,
-            sfr::imu::mag_z); // data in uT
+            sfr::imu::mag_z); // Data in uT
     }
 }
\ No newline at end of file
diff --git a/src/constants.hpp b/src/constants.hpp
index 7730d44..4cf7f89 100644
--- a/src/constants.hpp
+++ b/src/constants.hpp
@@ -12,15 +12,15 @@ namespace constants {
         constexpr int radio_di0_pin = 2;
         constexpr int radio_rst_pin = 5;
         constexpr int radio_busy_pin = 16;
-        // TODO: Document units
-        constexpr float freq = 437.4;
-        constexpr float bw = 62.5;
-        constexpr int sf = 10;
-        constexpr int cr = 5;
-        constexpr int sw = 18;
-        constexpr int pwr = 20;
-        constexpr int pl = 8;
-        constexpr int gn = 0;
+
+        constexpr float freq = 437.4; // MHz
+        constexpr float bw = 62.5;    // kHz
+        constexpr int sf = 10;        // Between 7 and 12
+        constexpr int cr = 5;         // Between 5 and 8. 4/8 coding ratio. One redundancy bit for every data bit
+        constexpr int sw = 18;        // Sync-word (defines network). Default is 0d18
+        constexpr int pwr = 20;       // Between 2 and 17, or 20 for max power
+        constexpr int pl = 8;         // Payload length
+        constexpr int gn = 0;         // Gain
 
         constexpr uint8_t max_alive_signal_dlinks = 3;
 
@@ -35,14 +35,14 @@ namespace constants {
         constexpr uint32_t callsign_interval = 10 * constants::time::one_minute;
 
         constexpr uint32_t transmit_slot_length = 700; // ms
-    // TODO: Verify sensor data on alive signal
+        // TODO: Verify sensor data on alive signal
     } // namespace radio
     namespace imu {
-        constexpr int gyro_min = -245; // default gyro range is +/- 245 dps
+        constexpr int gyro_min = -245; // Default gyro range is +/- 245 dps
         constexpr int gyro_max = 245;
-        constexpr int acc_min = -20; // default accel range is +/- 2 G
+        constexpr int acc_min = -20; // Default accel range is +/- 2 G
         constexpr int acc_max = 20;
-        constexpr int mag_min = -100; // default mag range is +/- 4 guass -> 100 uT
+        constexpr int mag_min = -100; // Default mag range is +/- 4 guass -> 100 uT
         constexpr int mag_max = 100;
     } // namespace imu
     namespace temperature {
@@ -63,12 +63,10 @@ namespace constants {
         constexpr uint8_t no_op = 0x00;
         constexpr uint8_t change_downlink_window = 0x11;
     } // namespace opcodes
-
     namespace led {
         constexpr int led_pin = 9;
         constexpr uint32_t led_on_time = 5 * constants::time::one_second;
     } // namespace led
-
-}; // namespace constants
+};    // namespace constants
 
 #endif
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index a1ebf0c..da9097a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -5,7 +5,7 @@ MainControlLoop mcl;
 
 void setup()
 {
-    // configure watchdog timer
+    // Set up watchdog timer
     wdt_disable();
     wdt_enable(WDTO_8S);
 #ifdef VERBOSE
@@ -14,19 +14,19 @@ void setup()
 
     sfr::gps::boot_time = millis();
 
-    // sets ChipSat LED high for debugging
+    // Set ChipSat LED high for debugging
     pinMode(constants::led::led_pin, OUTPUT);
     digitalWrite(constants::led::led_pin, HIGH);
 
-    // cuts off power to GPS
+    // Cut off power to GPS
     pinMode(constants::gps::reset_pin, OUTPUT);
     digitalWrite(constants::gps::reset_pin, HIGH);
 
-    // prevents current from leaking over GPS serial line (~79mA -> ~22mA)
+    // Prevents current from leaking over GPS serial line (~79mA -> ~22mA)
     pinMode(constants::gps::tx_pin, OUTPUT);
     digitalWrite(constants::gps::tx_pin, LOW);
 
-    // seed random number gen with noise from unconnected analog pin
+    // Seed random number gen with noise from unconnected analog pin
     randomSeed(analogRead(A0));
 }
 
diff --git a/src/sfr.cpp b/src/sfr.cpp
index 51d0e9e..210b713 100644
--- a/src/sfr.cpp
+++ b/src/sfr.cpp
@@ -1,17 +1,14 @@
 #include "sfr.hpp"
 
 namespace sfr {
-
     namespace imu {
+        bool initialized = false;
 
         float gyro_x, gyro_y, gyro_z;
         float acc_x, acc_y, acc_z;
         float mag_x, mag_y, mag_z;
 
-        bool initialized = false;
-
     } // namespace imu
-
     namespace temperature {
         float temp_c;
     } // namespace temperature
@@ -31,7 +28,6 @@ namespace sfr {
         uint8_t alive_signal_dlinks = 0;
 
         // This must be a multiple of constants::radio::transmit_slot_length
-        // Ideally window should be 10x the slot length
         uint32_t downlink_window_length = 3500; // ms
         uint32_t downlink_window_start;
         uint32_t listen_period_start;
@@ -45,5 +41,4 @@ namespace sfr {
         uint8_t invalid_uplinks = 0;
 
     } // namespace radio
-
-}; // namespace sfr
+};    // namespace sfr
diff --git a/src/sfr.hpp b/src/sfr.hpp
index bef501f..2ad9c83 100644
--- a/src/sfr.hpp
+++ b/src/sfr.hpp
@@ -7,6 +7,8 @@
 
 namespace sfr {
     namespace imu {
+        extern bool initialized;
+
         extern float gyro_x;
         extern float gyro_y;
         extern float gyro_z;
@@ -19,7 +21,6 @@ namespace sfr {
         extern float mag_y;
         extern float mag_z;
 
-        extern bool initialized;
     } // namespace imu
     namespace temperature {
         extern float temp_c;
@@ -56,7 +57,6 @@ namespace sfr {
 
         extern uint32_t boot_time;
     } // namespace gps
-
-}; // namespace sfr
+};    // namespace sfr
 
 #endif
\ No newline at end of file