Adding initial UDP tansport

pstop_c/CMakeLists.txt

@@ -4,3 +4,19 @@ cmake_minimum_required(VERSION 3.12)
 project(PSTOP C)
 
 add_subdirectory(pstop)
+add_subdirectory(transport)
+
+add_executable(machine_app
+  examples/machine/machine_app.c
+)
+
+target_include_directories(machine_app PUBLIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/pstop/include
+  ${CMAKE_CURRENT_SOURCE_DIR}/transport/include
+  include
+)
+
+target_link_libraries(machine_app PUBLIC
+  pstop
+  transport_udp
+)

pstop_c/examples/machine/machine_app.c

@@ -0,0 +1,70 @@
+
+// SPDX-FileCopyrightText: 2026 Polymath Robotics, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+#include <stdio.h>
+
+#include "transport/udp/udp_transport.h"
+#include "pstop/machine.h"
+#include "pstop/pstop_msg.h"
+
+pstop_application_t pstop_app;
+
+#define MAX_CLIENTS 3U
+
+pstop_client_data_t pstop_clients[MAX_CLIENTS];
+
+pstop_machine_t machine;
+
+udp_transport_data_t udp_transport;
+
+int is_operator_allowed(const device_id_t *device_id)
+{
+    return 1;
+}
+
+int
+main(int argc, char *argv[])
+{
+    transport_init_udp(&udp_transport);
+    pstop_application_init(&pstop_app);
+
+    pstop_app.app_config.default_timeout_ms = 1000U;
+    pstop_app.operator_allowed_cb = is_operator_allowed;
+
+    machine_init(&machine, &pstop_app, pstop_clients, MAX_CLIENTS);
+
+    int result = transport_udp_open(&udp_transport, "localhost", 8890);
+    if(result < 0) {
+        fprintf(stderr, "Unable to open UDP: %d\n", result);
+        return -1;
+    }
+
+    uint8_t reqbytes[PSTOP_MESSAGE_SIZE];
+    uint8_t respbytes[PSTOP_MESSAGE_SIZE];
+
+    pstop_msg_t req_msg;
+    pstop_msg_t resp_msg;
+    pstop_msg_t *resp_msg_ptr = &resp_msg;
+
+    fprintf(stderr, "Connected to localhost:8890\n");
+    while(1) {
+        struct sockaddr_storage client;
+        result = transport_udp_read(&udp_transport, reqbytes, PSTOP_MESSAGE_SIZE, &client);
+
+        if(result == PSTOP_MESSAGE_SIZE) {
+            pstop_message_encode(&req_msg, reqbytes);
+
+            pstop_error_t error = machine.handle_protocol_message_cb(&machine, &req_msg, &resp_msg_ptr);
+            if(resp_msg_ptr != NULL) {
+                pstop_message_encode(&resp_msg, respbytes);
+                transport_udp_write(&udp_transport, respbytes, PSTOP_MESSAGE_SIZE, (struct sockaddr_in *)&client);
+            }
+        }
+        machine.check_heartbeats_cb(&machine);
+    }
+
+    transport_udp_close(&udp_transport);
+
+    return 0;
+}

pstop_c/pstop/CMakeLists.txt

@@ -25,6 +25,7 @@ add_executable(pstop_test
   test/src/pstop/machine_test.c
   test/src/pstop/machine_timeout_test.c
   test/src/pstop/pstop_client_test.c
+  test/src/pstop/pstop_msg_test.c
 
   test/src/pstop/test_utils.c
 

pstop_c/pstop/include/pstop/device_id.h

@@ -17,6 +17,8 @@ typedef struct {
  */
 void device_id_init(device_id_t *device_id);
 
+void device_id_set_bytes(device_id_t *device_id, const uint8_t *data);
+
 /**
  * Copies the device ID from id to device_id.
  */

pstop_c/pstop/include/pstop/pstop_msg.h

@@ -15,13 +15,25 @@ typedef uint8_t message_type_t;
 #define PSTOP_MESSAGE_STOP 1U
 #define PSTOP_MESSAGE_BOND 2U
 #define PSTOP_MESSAGE_UNBOND 3U
-#define PSTOP_MESSAGE_UNKNOWN 0xFFU
+#define PSTOP_MESSAGE_UNKNOWN 0x0FU
+
+#define PSTOP_MESSAGE_SIZE 64U
 
 /**
  * A PSTOP message object. With enough information
  * to provide basic black channel support.
  */
 typedef struct {
+    /**
+     * Version of this message. Currently just 0x0
+     */
+    uint8_t version;
+
+    /**
+     * Type of message.
+     */
+    message_type_t message;
+
     /**
      * The timestamp (in milliseconds) of this message.
      */
@@ -45,7 +57,7 @@ typedef struct {
 
     /**
      * A timeout in milliseconds that we expect to receive heartbeats from
-     * this machine. Only valiud when sent from machine to operator.
+     * this machine. Only valid when sent from machine to operator.
      */
     uint32_t heartbeat_timeout;
 
@@ -60,11 +72,6 @@ typedef struct {
      */
     uint32_t received_counter;
 
-    /**
-     * The type of message.
-     */
-    message_type_t message;
-
     /**
      * a CRC-16 checksum of the above values.
      */
@@ -78,4 +85,10 @@ uint16_t pstop_calculate_checksum(const pstop_msg_t *msg);
 
 pstop_error_t pstop_is_message_valid(const pstop_msg_t *msg);
 
+/**
+ * Network encoding/decoding functions
+ */
+void pstop_message_decode(pstop_msg_t *msg, const uint8_t *data);
+void pstop_message_encode(const pstop_msg_t *msg, uint8_t *data);
+
 #endif /* PSTOP_PSTOP_MSG_H */

pstop_c/pstop/src/pstop/device_id.c

@@ -12,6 +12,12 @@ device_id_init(device_id_t *device_id)
     memset(device_id->data, 0, sizeof(device_id_t));
 }
 
+void
+device_id_set_bytes(device_id_t *device_id, const uint8_t *data)
+{
+    memcpy(device_id->data, data, DEVICE_ID_LENGTH);
+}
+
 void
 device_id_copy(device_id_t *device_id, const device_id_t *id)
 {

pstop_c/pstop/src/pstop/pstop_application.c

@@ -19,7 +19,7 @@ pstop_application_config_init(pstop_application_config_t *config)
 {
     config->default_timeout_ms = 100U;
     config->max_lost_messages = 1U;
-    config->max_missed_heartbeats = 0U;
+    config->max_missed_heartbeats = 1U;
 }
 
 void