lib: sgp4: move SGP4 from app module to shared library

simensrostad · simensrostad · commit 47257ddef720 · 2026-05-27T12:31:55.000+02:00
Move the SGP4 implementation from `app/src/modules/sgp4` to a new
`lib/sgp4` library so it can be used as a proper Zephyr library,
decoupled from the app module system.

The new library splits `SGP4_PASS_PREDICT` into a separate Kconfig
option. Tests are updated to use the new library path and enable
`CONFIG_SGP4_PASS_PREDICT` via `prj.conf` instead of directly
including source files.

Also removes the `at_monitor` dependency from `sgp4_pass_predict.c`.

Signed-off-by: Simen S. Røstad &lt;simen.rostad@nordicsemi.no&gt;
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -4,4 +4,5 @@
 # This CMake file is picked by the Zephyr build system because it is defined
 # as the module CMake entry point (see zephyr/module.yml).
 
+add_subdirectory(lib)
 add_subdirectory_ifdef(CONFIG_APP_CLOUD_MQTT examples/modules/cloud/)
diff --git a/Kconfig b/Kconfig
@@ -5,4 +5,5 @@
 # as the module Kconfig entry point (see zephyr/module.yml). You can browse
 # module options by going to Zephyr -> Modules in Kconfig.
 
+rsource "lib/Kconfig"
 rsource "examples/modules/cloud/Kconfig.cloud_mqtt"
diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
@@ -29,4 +29,3 @@ add_subdirectory_ifdef(CONFIG_APP_LOCATION src/modules/location)
 add_subdirectory_ifdef(CONFIG_APP_CLOUD src/modules/cloud)
 add_subdirectory_ifdef(CONFIG_APP_FOTA src/modules/fota)
 add_subdirectory_ifdef(CONFIG_APP_STORAGE src/modules/storage)
-add_subdirectory_ifdef(CONFIG_APP_SGP4 src/modules/sgp4)
diff --git a/app/Kconfig b/app/Kconfig
@@ -16,7 +16,6 @@ rsource "src/modules/fota/Kconfig.fota"
 rsource "src/modules/environmental/Kconfig.environmental"
 rsource "src/modules/button/Kconfig.button"
 rsource "src/modules/storage/Kconfig.storage"
-rsource "src/modules/sgp4/Kconfig.sgp4"
 rsource "memfault/Kconfig.memfault"
 
 endmenu
diff --git a/app/src/modules/sgp4/CMakeLists.txt b/app/src/modules/sgp4/CMakeLists.txt
diff --git a/app/src/modules/sgp4/Kconfig.sgp4 b/app/src/modules/sgp4/Kconfig.sgp4
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
@@ -0,0 +1,7 @@
+#
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+add_subdirectory_ifdef(CONFIG_SGP4 sgp4)
diff --git a/lib/Kconfig b/lib/Kconfig
@@ -0,0 +1,11 @@
+#
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+menu "Libraries"
+
+rsource "sgp4/Kconfig"
+
+endmenu
diff --git a/lib/sgp4/CMakeLists.txt b/lib/sgp4/CMakeLists.txt
@@ -0,0 +1,10 @@
+#
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+zephyr_library()
+zephyr_library_sources(SGP4.c)
+zephyr_library_sources_ifdef(CONFIG_SGP4_PASS_PREDICT sgp4_pass_predict.c)
+zephyr_library_include_directories(${CMAKE_CURRENT_SOURCE_DIR})
diff --git a/lib/sgp4/Kconfig b/lib/sgp4/Kconfig
@@ -0,0 +1,18 @@
+#
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+config SGP4
+	bool "SGP4 satellite propagation library"
+	help
+	  Enable Vallado SGP4 analytical orbit propagation (SGP4.c).
+
+config SGP4_PASS_PREDICT
+	bool "SGP4 satellite pass prediction"
+	default n
+	select SGP4
+	select DATE_TIME
+	help
+	  Enable satellite pass prediction using SGP4 and TLE/SIB32 data.
diff --git a/lib/sgp4/SGP4.c b/lib/sgp4/SGP4.c
diff --git a/lib/sgp4/SGP4.h b/lib/sgp4/SGP4.h
diff --git a/lib/sgp4/sgp4_pass_predict.c b/lib/sgp4/sgp4_pass_predict.c
@@ -15,7 +15,6 @@
 #include "sgp4_pass_predict.h"
 #include "SGP4.h"
 
-#include <modem/at_monitor.h>
 #include <zephyr/logging/log.h>
 
 #define DEG2RAD (3.14159265358979323846 / 180.0)
diff --git a/lib/sgp4/sgp4_pass_predict.h b/lib/sgp4/sgp4_pass_predict.h
diff --git a/tests/module/ntn-sib32/CMakeLists.txt b/tests/module/ntn-sib32/CMakeLists.txt
@@ -14,12 +14,11 @@ test_runner_generate(src/test_sib32_tle.c)
 target_sources(app
   PRIVATE
   src/test_sib32_tle.c
-  ../../../app/src/modules/sgp4/SGP4.c
 )
 
 zephyr_include_directories(${ZEPHYR_BASE}/include/zephyr/)
 zephyr_include_directories(${ZEPHYR_BASE}/subsys/testsuite/include)
 zephyr_include_directories(../../../app/src/common)
-zephyr_include_directories(../../../app/src/modules/sgp4)
+zephyr_include_directories(../../../lib/sgp4)
 
 target_link_options(app PRIVATE --whole-archive)
diff --git a/tests/module/ntn-sib32/prj.conf b/tests/module/ntn-sib32/prj.conf
@@ -4,6 +4,8 @@
 # SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 #
 
+CONFIG_SGP4_PASS_PREDICT=y
+CONFIG_DATE_TIME_NTP=n
 CONFIG_UNITY=y
 CONFIG_LOG=y
 CONFIG_CBPRINTF_FP_SUPPORT=y
diff --git a/tests/module/ntn-sib32/src/test_sib32_tle.c b/tests/module/ntn-sib32/src/test_sib32_tle.c
@@ -19,7 +19,6 @@
 struct tm *gmtime_r(const int64_t *timep, struct tm *result);
 char *strtok_r(char *str, const char *delim, char **saveptr);
 
-#include "../../../app/src/modules/sgp4/sgp4_pass_predict.c"
 
 DEFINE_FFF_GLOBALS;
 
diff --git a/tests/module/ntn/CMakeLists.txt b/tests/module/ntn/CMakeLists.txt
@@ -14,12 +14,11 @@ test_runner_generate(src/sgp4_pass_test.c)
 target_sources(app
   PRIVATE
   src/sgp4_pass_test.c
-  ../../../app/src/modules/sgp4/SGP4.c
 )
 
 zephyr_include_directories(${ZEPHYR_BASE}/include/zephyr/)
 zephyr_include_directories(${ZEPHYR_BASE}/subsys/testsuite/include)
 zephyr_include_directories(../../../app/src/common)
-zephyr_include_directories(../../../app/src/modules/sgp4)
+zephyr_include_directories(../../../lib/sgp4)
 
 target_link_options(app PRIVATE --whole-archive)
diff --git a/tests/module/ntn/prj.conf b/tests/module/ntn/prj.conf
@@ -4,6 +4,8 @@
 # SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 #
 
+CONFIG_SGP4_PASS_PREDICT=y
+CONFIG_DATE_TIME_NTP=n
 CONFIG_UNITY=y
 CONFIG_LOG=y
 CONFIG_CBPRINTF_FP_SUPPORT=y
diff --git a/tests/module/ntn/src/sgp4_pass_test.c b/tests/module/ntn/src/sgp4_pass_test.c
@@ -19,7 +19,6 @@
 struct tm *gmtime_r(const int64_t *timep, struct tm *result);
 char *strtok_r(char *str, const char *delim, char **saveptr);
 
-#include "../../../app/src/modules/sgp4/sgp4_pass_predict.c"
 
 DEFINE_FFF_GLOBALS;
 
