system/microros: Add UDP and serial custom transports with publisher example by arjav1528 · Pull Request #3512 · apache/nuttx-apps

arjav1528 · 2026-05-30T17:44:42Z

Phase 4 of micro-ROS-on-NuttX. Adds the transport callbacks Micro
XRCE-DDS needs and a minimal publisher example. Split into 4 commits:

system/microros: Fix toolchain attribute strip breaking libc inlines.
Drop -D'__attribute__(x)=' from toolchain.cmake.in. The strip
also removed __gnu_inline__ from NuttX libc string.h inlines,
causing ~50 multiple-definition errors at sim final link.
system/microros: Wire libmicroros include layout and sim final link.
Enumerate include/* subdirs so both <rcl/rcl.h> (nested colcon
layout) and <rclc/rclc.h> (flat) resolve. Switch LDLIBS →
EXTRA_LIBS so the sim final link picks up libmicroros.a.
system/microros: Add UDP and serial custom transport backends.
New transport/ dispatcher + UDP (BSD sockets, unconnected
sendto/recvfrom so host-mode docker agent replies are accepted)
- serial (termios, raw 8N1). Wired into Make and CMake
  (cmake-format clean).
examples/microros_pub: Add minimal Int32 publisher example.
30 std_msgs/Int32 messages on /nuttx_pub at 1 Hz, then clean
fini. Smoke test for the transport layer.

Impact

Fixes a pre-existing sim final-link regression in system/microros
(apps/system/microros: add libmicroros.a colcon cross-build orchestration #3498); any non-trivial micro-ROS sim build was broken before this.
New Kconfig: MICROROS_TRANSPORT_{UDP,SERIAL}, MICROROS_AGENT_IP,
MICROROS_AGENT_PORT, MICROROS_SERIAL_DEVICE,
MICROROS_SERIAL_BAUD. Default off — no change for existing configs.
UDP backend needs CONFIG_NET_UDP; serial backend needs a TTY.

Dependencies

Depends on companion nuttx PR
[tools/nxstyle: Whitelist ROS 2 message type identifiers.]
(branch tools-nxstyle-microros-whitelist). Without it, nxstyle
flags two unavoidable mixed-case identifiers in
examples/microros_pub/microros_pub_main.c
(std_msgs__msg__Int32 and the Int32 macro arg to
ROSIDL_GET_MSG_TYPE_SUPPORT) — both are upstream rosidl
token-pasted symbols that cannot be renamed.

Testing

Ubuntu 22.04 EC2, sim:nsh + CONFIG_SYSTEM_MICROROS=y +
MICROROS_TRANSPORT_UDP=y + EXAMPLES_MICROROS_PUB=y. TAP
networking, host 192.168.10.1, NuttX 192.168.10.2. Agent
micro-ros/micro-ros-agent:jazzy in docker --network host, UDP4
port 8888.

phase3.log
phase4_agent.log
phase4_bootstrap.log
phase4_make_context.log

phase4.log — NSH session, 30/30 publishes + done.
phase4_agent.log — session establish, publisher create, 30 ACKs,
clean destroy.
phase4_bootstrap.log, phase4_make_context.log — build.

Excerpt:

nsh> microros_pub
microros_pub: starting
microros_pub: sent 0
...
microros_pub: sent 29
microros_pub: done

nxstyle (with companion patch applied) clean on all 8 touched
C/H files. cmake-format clean on system/microros/CMakeLists.txt.

Not verified: serial backend on hardware — I dont have the
hardware needed.

acassis · 2026-05-30T19:14:23Z

@arjav1528 after apache/nuttx#19001 get merged, please rebase to git push -f to fix the CI Check error.

arjav1528 · 2026-05-30T19:22:22Z

@arjav1528 after apache/nuttx#19001 get merged, please rebase to git push -f to fix the CI Check error.

ya, sure, thats what I was gonna do

xiaoxiang781216 · 2026-05-31T03:28:49Z

+
+config EXAMPLES_MICROROS_PUB_STACKSIZE
+	int "micro-ROS pub stack size"
+	default 16384


do we really need so big stack

xiaoxiang781216 · 2026-05-31T03:31:21Z

+ ****************************************************************************/
+
+static rcl_publisher_t        g_publisher;
+static std_msgs__msg__Int32   g_msg;


change to local variables

xiaoxiang781216 · 2026-05-31T03:31:40Z

@@ -0,0 +1,32 @@
+############################################################################
+# apps/examples/microros_pub/Makefile


add cmake build file

xiaoxiang781216 · 2026-05-31T03:34:58Z

+#if defined(CONFIG_MICROROS_TRANSPORT_UDP)
+  rmw_uros_set_custom_transport(false,
+                                NULL,
+                                (open_custom_func)microros_udp_open,


remove ALL cast

xiaoxiang781216 · 2026-05-31T03:35:35Z

+                                (write_custom_func)microros_udp_write,
+                                (read_custom_func)microros_udp_read);
+  return 0;
+#elif defined(CONFIG_MICROROS_TRANSPORT_SERIAL)


can/should we support the multiple transport at the same time

xiaoxiang781216 · 2026-05-31T03:41:36Z

+      return 0;
+    }
+
+  return (size_t)n;


remove the cast

xiaoxiang781216 · 2026-05-31T03:41:49Z

+      return 0;
+    }
+
+  return (size_t)n;


xiaoxiang781216 · 2026-05-31T03:43:30Z

+MICROROS_INC_DIRS := $(APPDIR)/system/microros/include \
+                     $(wildcard $(APPDIR)/system/microros/include/*)
+CFLAGS   += $(foreach d,$(MICROROS_INC_DIRS),${INCDIR_PREFIX}$(d))
+CFLAGS   += ${INCDIR_PREFIX}$(APPDIR)/system/microros/transport


move to Makefile to avoid expose $(APPDIR)/system/microros/transport to public search path

xiaoxiang781216 · 2026-05-31T03:43:37Z

+CFLAGS   += $(foreach d,$(MICROROS_INC_DIRS),${INCDIR_PREFIX}$(d))
+CFLAGS   += ${INCDIR_PREFIX}$(APPDIR)/system/microros/transport
+CXXFLAGS += $(foreach d,$(MICROROS_INC_DIRS),${INCDIR_PREFIX}$(d))
+CXXFLAGS += ${INCDIR_PREFIX}$(APPDIR)/system/microros/transport


xiaoxiang781216 · 2026-05-31T03:43:53Z


-CFLAGS   += ${INCDIR_PREFIX}$(APPDIR)/system/microros/include
-CXXFLAGS += ${INCDIR_PREFIX}$(APPDIR)/system/microros/include
+MICROROS_INC_DIRS := $(APPDIR)/system/microros/include \


merge to previous patch

micro_ros_lib/toolchain.cmake.in initialised C and CXX flags with -D'__attribute__(x)=' to silence GCC attributes the upstream ament build is not aware of. The strip also removed __gnu_inline__ and __always_inline__ from NuttX's libc string.h inlines, so each micro-ROS translation unit emitted external definitions of strcmp, strcpy, strlen and friends. Sim final link then failed with ~50 multiple-definition errors. Drop the define from both flag init lines so the attributes survive and the inlines collapse as intended. Signed-off-by: Arjav Patel <arjav1528@gmail.com>

libmicroros is installed by colcon under include/<pkg>/<pkg>/file.h for ament-packaged headers (e.g. rcl, rmw, rosidl) and the flat include/<pkg>/file.h for a few others (e.g. rclc). A single -I include/ therefore resolves <rclc/rclc.h> but not <rcl/rcl.h>. Enumerate every immediate subdirectory of include/ in addition to include/ itself so both layouts resolve. Switch the library hand-off from LDLIBS to EXTRA_LIBS. The sim target's final link pulls EXTRA_LIBS, not LDLIBS, so the previous form left rcl/rclc/rcutils symbols unresolved. Signed-off-by: Arjav Patel <arjav1528@gmail.com>

Micro XRCE-DDS expects the application to supply open/close/write/read callbacks for the wire transport. Add a single dispatcher that registers the selected backend via rmw_uros_set_custom_transport(), plus two backends: transport/microros_transport_udp.c BSD-socket UDP backend. Opens an AF_INET/SOCK_DGRAM socket, resolves CONFIG_MICROROS_AGENT_IP/PORT, connect()s it, and uses send/recv. The socket fd is stashed in uxrCustomTransport->args so no module-level state is needed. transport/microros_transport_serial.c termios serial backend. Opens CONFIG_MICROROS_SERIAL_DEVICE with O_RDWR|O_NOCTTY|O_CLOEXEC, switches to raw 8N1 at CONFIG_MICROROS_SERIAL_BAUD, and uses poll/read/write. Fd is again stashed in uxrCustomTransport->args. Both backends are mutually exclusive at compile time via Kconfig; the dispatcher selects which set of callbacks to register. Wired into both the legacy Make build (CSRCS in system/microros/Makefile) and the CMake build (separate microros_transport static library with the transport directory only exposed to its INTERFACE). Signed-off-by: Arjav Patel <arjav1528@gmail.com>

End-to-end exercise of the micro-ROS stack on NuttX: calls microros_transport_init() to register the configured backend, brings up rclc_support / node / publisher, publishes 30 std_msgs/Int32 messages on /nuttx_pub at 1 Hz, then tears the stack down cleanly. The example's Make.defs adds $(APPDIR)/system/microros/transport to its own CFLAGS rather than the system/microros Make.defs, so the transport-glue header path is not pushed into the global search path for unrelated apps. Serves as the smoke test for the transport layer and as a template for downstream publisher apps. Signed-off-by: Arjav Patel <arjav1528@gmail.com>

github-actions Bot added Size: L Area: System Area: Examples labels May 30, 2026

arjav1528 force-pushed the micro-ros-custom-transport branch 2 times, most recently from acb130d to 4ad5643 Compare May 30, 2026 18:01

arjav1528 mentioned this pull request May 30, 2026

tools/nxstyle: Whitelist ROS 2 message type identifiers. apache/nuttx#19001

Merged

xiaoxiang781216 reviewed May 31, 2026

View reviewed changes

arjav1528 added 4 commits May 31, 2026 10:11

arjav1528 force-pushed the micro-ros-custom-transport branch from 4ad5643 to dfdd36f Compare May 31, 2026 06:46

arjav1528 mentioned this pull request May 31, 2026

tools/nxstyle: Whitelist Micro XRCE-DDS uxrCustomTransport prefix apache/nuttx#19006

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system/microros: Add UDP and serial custom transports with publisher example#3512

system/microros: Add UDP and serial custom transports with publisher example#3512
arjav1528 wants to merge 4 commits into
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arjav1528 commented May 30, 2026 •

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		@@ -0,0 +1,32 @@
		############################################################################
		# apps/examples/microros_pub/Makefile

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arjav1528 commented May 30, 2026 •

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