[hal] Expose CAN timestamp base clock (#5357)

hal/src/main/java/edu/wpi/first/hal/CANAPIJNI.java

@@ -5,6 +5,8 @@
 package edu.wpi.first.hal;
 
 public class CANAPIJNI extends JNIWrapper {
+  public static native long getCANPacketBaseTime();
+
   public static native int initializeCAN(int manufacturer, int deviceId, int deviceType);
 
   public static native void cleanCAN(int handle);

hal/src/main/java/edu/wpi/first/hal/CANData.java

@@ -6,16 +6,19 @@ package edu.wpi.first.hal;
 
 @SuppressWarnings("MemberName")
 public class CANData {
+  /** Contents of the CAN frame. */
   public final byte[] data = new byte[8];
+  /** Length of the frame in bytes. */
   public int length;
+  /** CAN frame timestamp in milliseconds. */
   public long timestamp;
 
   /**
    * API used from JNI to set the data.
    *
    * @param length Length of packet in bytes.
-   * @param timestamp CAN frame timestamp in microseconds.
-   * @return Buffer containing CAN frame.
+   * @param timestamp CAN frame timestamp in milliseconds.
+   * @return Buffer to place CAN frame data in.
    */
   @SuppressWarnings("PMD.MethodReturnsInternalArray")
   public byte[] setData(int length, long timestamp) {

hal/src/main/native/athena/CANAPI.cpp

@@ -35,15 +35,6 @@ struct CANStorage {
 static UnlimitedHandleResource<HAL_CANHandle, CANStorage, HAL_HandleEnum::CAN>*
     canHandles;
 
-static uint32_t GetPacketBaseTime() {
-  timespec t;
-  clock_gettime(CLOCK_MONOTONIC, &t);
-
-  // Convert t to milliseconds
-  uint64_t ms = t.tv_sec * 1000ull + t.tv_nsec / 1000000ull;
-  return ms & 0xFFFFFFFF;
-}
-
 namespace hal::init {
 void InitializeCANAPI() {
   static UnlimitedHandleResource<HAL_CANHandle, CANStorage, HAL_HandleEnum::CAN>
@@ -63,6 +54,15 @@ static int32_t CreateCANId(CANStorage* storage, int32_t apiId) {
 
 extern "C" {
 
+uint32_t HAL_GetCANPacketBaseTime(void) {
+  timespec t;
+  clock_gettime(CLOCK_MONOTONIC, &t);
+
+  // Convert t to milliseconds
+  uint64_t ms = t.tv_sec * 1000ull + t.tv_nsec / 1000000ull;
+  return ms & 0xFFFFFFFF;
+}
+
 HAL_CANHandle HAL_InitializeCAN(HAL_CANManufacturer manufacturer,
                                 int32_t deviceId, HAL_CANDeviceType deviceType,
                                 int32_t* status) {
@@ -267,7 +267,7 @@ void HAL_ReadCANPacketTimeout(HAL_CANHandle handle, int32_t apiId,
     auto i = can->receives.find(messageId);
     if (i != can->receives.end()) {
       // Found, check if new enough
-      uint32_t now = GetPacketBaseTime();
+      uint32_t now = HAL_GetCANPacketBaseTime();
       if (now - i->second.lastTimeStamp > static_cast<uint32_t>(timeoutMs)) {
         // Timeout, return bad status
         *status = HAL_CAN_TIMEOUT;

hal/src/main/native/cpp/jni/CANAPIJNI.cpp

@@ -18,6 +18,18 @@ using namespace hal;
 using namespace wpi::java;
 
 extern "C" {
+
+/*
+ * Class:     edu_wpi_first_hal_CANAPIJNI
+ * Method:    getCANPacketBaseTime
+ * Signature: ()J
+ */
+JNIEXPORT jlong JNICALL
+Java_edu_wpi_first_hal_CANAPIJNI_getCANPacketBaseTime
+  (JNIEnv*, jclass)
+{
+  return HAL_GetCANPacketBaseTime();
+}
 /*
  * Class:     edu_wpi_first_hal_CANAPIJNI
  * Method:    initializeCAN

hal/src/main/native/include/hal/CANAPI.h

@@ -19,6 +19,15 @@
 extern "C" {
 #endif
 
+/**
+ * Reads the current value of the millisecond-resolution timer that the CAN API
+ * functions use as a time base.
+ *
+ * @return Current value of timer used as a base time by the CAN API in
+ * milliseconds.
+ */
+uint32_t HAL_GetCANPacketBaseTime(void);
+
 /**
  * Initializes a CAN device.
  *
@@ -111,8 +120,8 @@ void HAL_StopCANPacketRepeating(HAL_CANHandle handle, int32_t apiId,
  * @param[in] apiId              the ID to read (0-1023)
  * @param[out] data              the packet data (8 bytes)
  * @param[out] length            the received length (0-8 bytes)
- * @param[out] receivedTimestamp the packet received timestamp (based off of
- *                               CLOCK_MONOTONIC)
+ * @param[out] receivedTimestamp the packet received timestamp in ms (based off
+ *                               of CLOCK_MONOTONIC)
  * @param[out] status            Error status variable. 0 on success.
  */
 void HAL_ReadCANPacketNew(HAL_CANHandle handle, int32_t apiId, uint8_t* data,
@@ -127,8 +136,8 @@ void HAL_ReadCANPacketNew(HAL_CANHandle handle, int32_t apiId, uint8_t* data,
  * @param[in] apiId              the ID to read (0-1023)
  * @param[out] data              the packet data (8 bytes)
  * @param[out] length            the received length (0-8 bytes)
- * @param[out] receivedTimestamp the packet received timestamp (based off of
- *                               CLOCK_MONOTONIC)
+ * @param[out] receivedTimestamp the packet received timestamp in ms (based off
+ *                               of CLOCK_MONOTONIC)
  * @param[out] status            Error status variable. 0 on success.
  */
 void HAL_ReadCANPacketLatest(HAL_CANHandle handle, int32_t apiId, uint8_t* data,
@@ -144,8 +153,8 @@ void HAL_ReadCANPacketLatest(HAL_CANHandle handle, int32_t apiId, uint8_t* data,
  * @param[in] apiId              the ID to read (0-1023)
  * @param[out] data              the packet data (8 bytes)
  * @param[out] length            the received length (0-8 bytes)
- * @param[out] receivedTimestamp the packet received timestamp (based off of
- *                               CLOCK_MONOTONIC)
+ * @param[out] receivedTimestamp the packet received timestamp in ms (based off
+ *                               of CLOCK_MONOTONIC)
  * @param[out] timeoutMs         the timeout time for the packet
  * @param[out] status            Error status variable. 0 on success.
  */

hal/src/main/native/sim/CANAPI.cpp

@@ -35,13 +35,6 @@ struct CANStorage {
 static UnlimitedHandleResource<HAL_CANHandle, CANStorage, HAL_HandleEnum::CAN>*
     canHandles;
 
-static uint32_t GetPacketBaseTime() {
-  int status = 0;
-  auto basetime = HAL_GetFPGATime(&status);
-  // us to ms
-  return (basetime / 1000ull) & 0xFFFFFFFF;
-}
-
 namespace hal {
 namespace init {
 void InitializeCANAPI() {
@@ -71,6 +64,13 @@ static int32_t CreateCANId(CANStorage* storage, int32_t apiId) {
   return createdId;
 }
 
+uint32_t HAL_GetCANPacketBaseTime() {
+  int status = 0;
+  auto basetime = HAL_GetFPGATime(&status);
+  // us to ms
+  return (basetime / 1000ull) & 0xFFFFFFFF;
+}
+
 HAL_CANHandle HAL_InitializeCAN(HAL_CANManufacturer manufacturer,
                                 int32_t deviceId, HAL_CANDeviceType deviceType,
                                 int32_t* status) {
@@ -275,7 +275,7 @@ void HAL_ReadCANPacketTimeout(HAL_CANHandle handle, int32_t apiId,
     auto i = can->receives.find(messageId);
     if (i != can->receives.end()) {
       // Found, check if new enough
-      uint32_t now = GetPacketBaseTime();
+      uint32_t now = HAL_GetCANPacketBaseTime();
       if (now - i->second.lastTimeStamp > static_cast<uint32_t>(timeoutMs)) {
         // Timeout, return bad status
         *status = HAL_CAN_TIMEOUT;
@@ -307,7 +307,7 @@ void HAL_ReadCANPeriodicPacket(HAL_CANHandle handle, int32_t apiId,
     auto i = can->receives.find(messageId);
     if (i != can->receives.end()) {
       // Found, check if new enough
-      uint32_t now = GetPacketBaseTime();
+      uint32_t now = HAL_GetCANPacketBaseTime();
       if (now - i->second.lastTimeStamp < static_cast<uint32_t>(periodMs)) {
         *status = 0;
         // Read the data from the stored message into the output
@@ -337,7 +337,7 @@ void HAL_ReadCANPeriodicPacket(HAL_CANHandle handle, int32_t apiId,
     auto i = can->receives.find(messageId);
     if (i != can->receives.end()) {
       // Found, check if new enough
-      uint32_t now = GetPacketBaseTime();
+      uint32_t now = HAL_GetCANPacketBaseTime();
       if (now - i->second.lastTimeStamp > static_cast<uint32_t>(timeoutMs)) {
         // Timeout, return bad status
         *status = HAL_CAN_TIMEOUT;

wpilibc/src/main/native/cpp/CAN.cpp

@@ -131,3 +131,7 @@ bool CAN::ReadPacketTimeout(int apiId, int timeoutMs, CANData* data) {
     return true;
   }
 }
+
+uint64_t CAN::GetTimestampBaseTime() {
+  return HAL_GetCANPacketBaseTime();
+}

wpilibc/src/main/native/include/frc/CAN.h

@@ -10,8 +10,11 @@
 
 namespace frc {
 struct CANData {
+  /** Contents of the CAN packet. */
   uint8_t data[8];
+  /** Length of packet in bytes. */
   int32_t length;
+  /** CAN frame timestamp in milliseconds. */
   uint64_t timestamp;
 };
 
@@ -158,6 +161,15 @@ class CAN {
    */
   bool ReadPacketTimeout(int apiId, int timeoutMs, CANData* data);
 
+  /**
+   * Reads the current value of the millisecond-resolution timer that CANData
+   * timestamps are based on
+   *
+   * @return Current value of timer used as a base time for CANData timestamps
+   * in milliseconds
+   */
+  static uint64_t GetTimestampBaseTime();
+
   static constexpr HAL_CANManufacturer kTeamManufacturer = HAL_CAN_Man_kTeamUse;
   static constexpr HAL_CANDeviceType kTeamDeviceType =
       HAL_CAN_Dev_kMiscellaneous;

wpilibj/src/main/java/edu/wpi/first/wpilibj/CAN.java

@@ -172,4 +172,15 @@ public class CAN implements Closeable {
   public boolean readPacketTimeout(int apiId, int timeoutMs, CANData data) {
     return CANAPIJNI.readCANPacketTimeout(m_handle, apiId, timeoutMs, data);
   }
+
+  /**
+   * Reads the current value of the millisecond-resolution timer that {@link CANData} timestamps are
+   * based on.
+   *
+   * @return Current value of timer used as a base time for {@link CANData} timestamps in
+   *     milliseconds
+   */
+  public static long getTimestampBaseTime() {
+    return CANAPIJNI.getCANPacketBaseTime();
+  }
 }