fw: heart: Add zbus-based heartbeat code

The heartbeat of the firmware might be used for multiple purposes. It
can trigger a blinking LED on the PCB, can be displayed in a client
program or might serve additional purposes.

Since at least display in client programs should be implemented and
multiple clients should be support in long term it improves the code
structure to use a zbus channel here to publish heartbeat messages in a
publish-subscribe pattern.

That way the publishing of the heartbeat message and the receiving by an
unknown number of observers is completely decoupled. A central trait of
the publish-subscribe pattern and an advantage for a modular code
structure.

4 files changed, 79 insertions, 1 deletions

diff --git a/fw/CMakeLists.txt b/fw/CMakeLists.txt
index cffb6a1..b7a3783 100644
--- a/fw/CMakeLists.txt
+++ b/fw/CMakeLists.txt
@@ -23,6 +23,7 @@ target_sources(app
 		"${CMAKE_CURRENT_SOURCE_DIR}/src/syslog.c"
 		"${CMAKE_CURRENT_SOURCE_DIR}/src/mac.c"
 		"${CMAKE_CURRENT_SOURCE_DIR}/src/http.c"
+		"${CMAKE_CURRENT_SOURCE_DIR}/src/heart.c"
 )
 
 zephyr_linker_sources(SECTIONS sections-rom.ld)
diff --git a/fw/prj.conf b/fw/prj.conf
index bd761fc..7984caa 100644
--- a/fw/prj.conf
+++ b/fw/prj.conf
@@ -20,10 +20,15 @@ CONFIG_LOG_MODE_DEFERRED=y
 
 CONFIG_POSIX_C_LANG_SUPPORT_R=y
 
-CONFIG_HTTP_SERVER=y
 CONFIG_HTTP_PARSER=y
 CONFIG_HTTP_PARSER_URL=y
 
+CONFIG_HTTP_SERVER=y
+
 CONFIG_FILE_SYSTEM=y
 
 CONFIG_EVENTFD=y
+
+CONFIG_ZBUS=y
+CONFIG_ZBUS_MSG_SUBSCRIBER=y
+CONFIG_HEAP_MEM_POOL_SIZE=2048
diff --git a/fw/src/heart.c b/fw/src/heart.c
new file mode 100644
index 0000000..6bcced6
--- /dev/null
+++ b/fw/src/heart.c
@@ -0,0 +1,52 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+
+#include <stdbool.h>
+
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+
+#include "heart.h"
+
+
+LOG_MODULE_REGISTER(heart);
+
+
+#define HEART_PERIOD          K_MSEC(1000)
+#define HEART_STACK_SIZE               500
+#define HEART_PRIO       K_PRIO_PREEMPT(8)
+
+
+ZBUS_CHAN_DEFINE(
+	heartbeat_channel,
+	struct heartbeat,
+	NULL,
+	NULL,
+	ZBUS_OBSERVERS_EMPTY,
+	ZBUS_MSG_INIT(.ttl_ms = 0)
+);
+
+
+static void heart_thread_function(void *ptr1, void *ptr2, void *ptr3) {
+	LOG_INF("Starting to beat");
+
+	struct heartbeat heartbeat = {.ttl_ms = 1100};
+
+	while (true) {
+		LOG_DBG("Heart beat");
+		int ret = zbus_chan_pub(&heartbeat_channel, &heartbeat, K_FOREVER);
+		if (ret < 0) {
+			LOG_ERR("Could not publish heartbeat");
+		}
+		k_sleep(HEART_PERIOD);
+	}
+}
+
+
+K_THREAD_DEFINE(heart_thread, HEART_STACK_SIZE,
+                heart_thread_function, NULL, NULL, NULL,
+                HEART_PRIO, 0, 0);
diff --git a/fw/src/heart.h b/fw/src/heart.h
new file mode 100644
index 0000000..cd32c15
--- /dev/null
+++ b/fw/src/heart.h
@@ -0,0 +1,20 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef SRC_HEART_H
+#define SRC_HEART_H
+
+
+#include <zephyr/zbus/zbus.h>
+
+
+struct heartbeat {
+	uint32_t ttl_ms;
+};
+
+ZBUS_CHAN_DECLARE(heartbeat_channel);
+
+#endif // !SRC_HEART_H