Add test protobuf encoding with CRC and COBS

firmware/CMakeLists.txt

@@ -26,6 +26,14 @@ endif()
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(cloudburst)
 
+# Include nanopb for protobuf support
+list(APPEND CMAKE_MODULE_PATH ${ZEPHYR_BASE}/modules/nanopb)
+include(nanopb)
+
+# Generate protobuf sources from falcon-protos
+set(FALCON_PROTOS_DIR ${CMAKE_CURRENT_LIST_DIR}/../../modules/falcon-protos)
+zephyr_nanopb_sources(app ${FALCON_PROTOS_DIR}/HelloWorldPacket.proto)
+
 target_sources(app PRIVATE
   src/main.c
   src/data.c
@@ -41,6 +49,7 @@ target_sources(app PRIVATE
   src/state_machine/states/main_descent.c
   src/state_machine/states/landed.c
   src/pyro/pyro_thread.c
+  src/radio/radio_thread.c
 )
 
 target_include_directories(app PRIVATE

firmware/prj.conf

@@ -66,3 +66,12 @@ CONFIG_THREAD_MONITOR=y
 CONFIG_THREAD_NAME=y
 CONFIG_THREAD_STACK_INFO=n
 CONFIG_STACK_SENTINEL=y
+
+# Enable nanopb for protobuf support
+CONFIG_NANOPB=y
+
+# Enable CRC for packet integrity checking
+CONFIG_CRC=y
+
+# Enable COBS for packet framing
+CONFIG_COBS=y

firmware/src/main.c

@@ -8,6 +8,7 @@
 #include "logger_thread.h"
 #include "state_machine/state_machine.h"
 #include "pyro/pyro_thread.h"
+#include "radio/radio_thread.h"
 #include "data.h"
 
 LOG_MODULE_REGISTER(falcon_main, LOG_LEVEL_INF);
@@ -22,6 +23,7 @@ int main(void)
     start_baro_thread();
     start_pyro_thread();
     start_state_machine_thread();
+    start_radio_thread();
 
     return 0;
 }

firmware/src/radio/radio_thread.c

@@ -0,0 +1,98 @@
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/crc.h>
+#include <zephyr/data/cobs.h>
+#include <zephyr/net_buf.h>
+#include <pb_encode.h>
+#include <HelloWorldPacket.pb.h>
+
+LOG_MODULE_REGISTER(radio_thread, LOG_LEVEL_INF);
+
+#define RADIO_THREAD_STACK_SIZE 2048
+#define RADIO_THREAD_PRIORITY 5
+#define RADIO_THREAD_PERIOD_MS 1000
+
+#define MAX_COBS_SIZE    256 /* max size of COBS encoded data, defined by GNSS/RADIO SPI spec */
+#define MAX_FRAME_SIZE   ((MAX_COBS_SIZE - 2) * 254 / 255) /* 253 */
+#define MAX_PAYLOAD_SIZE (MAX_FRAME_SIZE - sizeof(uint16_t)) /* 251 */
+
+NET_BUF_POOL_DEFINE(cobs_src_pool, 1, MAX_FRAME_SIZE, 0, NULL);
+NET_BUF_POOL_DEFINE(cobs_dst_pool, 1, MAX_COBS_SIZE, 0, NULL);
+
+K_THREAD_STACK_DEFINE(radio_stack, RADIO_THREAD_STACK_SIZE);
+static struct k_thread radio_thread;
+
+BUILD_ASSERT(MAX_FRAME_SIZE + MAX_FRAME_SIZE / 254 + 2 <= MAX_COBS_SIZE,
+	     "MAX_FRAME_SIZE too large for MAX_COBS_SIZE");
+
+static void radio_thread_fn(void *p1, void *p2, void *p3)
+{
+	uint32_t counter = 0;
+
+	while (1) {
+		HelloWorldPacket message = HelloWorldPacket_init_zero;
+		uint8_t buffer[MAX_PAYLOAD_SIZE];
+
+		message.counter = counter;
+		strncpy(message.message, "hello world", sizeof(message.message) - 1);
+
+		pb_ostream_t stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
+		bool status = pb_encode(&stream, HelloWorldPacket_fields, &message);
+		size_t message_length = stream.bytes_written;
+
+		if (!status) {
+			LOG_ERR("Failed to encode HelloWorldPacket: %s",
+				PB_GET_ERROR(&stream));
+			counter++;
+			k_sleep(K_MSEC(RADIO_THREAD_PERIOD_MS));
+			continue;
+		}
+
+		/* CRC16-CCITT over protobuf payload */
+		uint16_t crc = crc16_ccitt(0x0000, buffer, message_length);
+
+		/* Pack protobuf data + CRC into net_buf for COBS encoding */
+		struct net_buf *src_buf = net_buf_alloc(&cobs_src_pool, K_NO_WAIT);
+		struct net_buf *dst_buf = net_buf_alloc(&cobs_dst_pool, K_NO_WAIT);
+
+		if (!src_buf || !dst_buf) {
+			LOG_ERR("Failed to allocate net_buf for COBS encoding");
+			if (src_buf) {
+				net_buf_unref(src_buf);
+			}
+			if (dst_buf) {
+				net_buf_unref(dst_buf);
+			}
+			counter++;
+			k_sleep(K_MSEC(RADIO_THREAD_PERIOD_MS));
+			continue;
+		}
+
+		net_buf_add_mem(src_buf, buffer, message_length);
+		net_buf_add_le16(src_buf, crc);
+
+		/* COBS encode with trailing 0x00 delimiter */
+		int ret = cobs_encode(src_buf, dst_buf, COBS_FLAG_TRAILING_DELIMITER);
+
+		if (ret == 0) {
+			LOG_INF("Encoded packet: counter=%u, pb=%zu, cobs=%u bytes",
+				counter, message_length, dst_buf->len);
+			LOG_HEXDUMP_DBG(dst_buf->data, dst_buf->len,
+					"COBS encoded packet");
+		} else {
+			LOG_ERR("COBS encoding failed: %d", ret);
+		}
+
+		net_buf_unref(src_buf);
+		net_buf_unref(dst_buf);
+
+		counter++;
+		k_sleep(K_MSEC(RADIO_THREAD_PERIOD_MS));
+	}
+}
+
+void start_radio_thread(void)
+{
+	k_thread_create(&radio_thread, radio_stack, K_THREAD_STACK_SIZEOF(radio_stack),
+			radio_thread_fn, NULL, NULL, NULL, RADIO_THREAD_PRIORITY, 0, K_NO_WAIT);
+}

firmware/src/radio/radio_thread.h

@@ -0,0 +1,6 @@
+#ifndef RADIO_THREAD_H
+#define RADIO_THREAD_H
+
+void start_radio_thread(void);
+
+#endif

west.yml

@@ -2,12 +2,18 @@ manifest:
   remotes:
     - name: zephyrproject-rtos
       url-base: https://github.com/zephyrproject-rtos
+    - name: ubc-rocket
+      url-base: https://github.com/UBC-Rocket
 
   projects:
     - name: zephyr
       remote: zephyrproject-rtos
       revision: v4.3.0
       import: true
+    - name: falcon-protos
+      remote: ubc-rocket
+      revision: main
+      path: modules/falcon-protos
 
   self:
     path: app