diff --git a/panda b/panda
index 2ae7b9a4d5..288e14cde9 160000
--- a/panda
+++ b/panda
@@ -1 +1 @@
-Subproject commit 2ae7b9a4d59101c0a1a9015feb3e835763db5686
+Subproject commit 288e14cde904a5755ebb32b0853631ac7fbf5968
diff --git a/selfdrive/boardd/panda.cc b/selfdrive/boardd/panda.cc
index 788cdf5cf1..db9bcbab51 100644
--- a/selfdrive/boardd/panda.cc
+++ b/selfdrive/boardd/panda.cc
@@ -169,22 +169,15 @@ static uint8_t len_to_dlc(uint8_t len) {
   }
 }
 
-static void write_packet(uint8_t *dest, int *write_pos, const uint8_t *src, size_t size) {
-  for (int i = 0, &pos = *write_pos; i < size; ++i, ++pos) {
-    // Insert counter every 64 bytes (first byte of 64 bytes USB packet)
-    if (pos % USBPACKET_MAX_SIZE == 0) {
-      dest[pos] = pos / USBPACKET_MAX_SIZE;
-      pos++;
-    }
-    dest[pos] = src[i];
-  }
-}
-
 void Panda::pack_can_buffer(const capnp::List<cereal::CanData>::Reader &can_data_list,
                             std::function<void(uint8_t *, size_t)> write_func) {
   int32_t pos = 0;
   uint8_t send_buf[2 * USB_TX_SOFT_LIMIT];
 
+  uint32_t magic = CAN_TRANSACTION_MAGIC;
+  memcpy(&send_buf[0], &magic, sizeof(uint32_t));
+  pos += sizeof(uint32_t);
+
   for (auto cmsg : can_data_list) {
     // check if the message is intended for this panda
     uint8_t bus = cmsg.getSrc();
@@ -202,16 +195,19 @@ void Panda::pack_can_buffer(const capnp::List<cereal::CanData>::Reader &can_data
     header.data_len_code = data_len_code;
     header.bus = bus - bus_offset;
 
-    write_packet(send_buf, &pos, (uint8_t *)&header, sizeof(can_header));
-    write_packet(send_buf, &pos, (uint8_t *)can_data.begin(), can_data.size());
+    memcpy(&send_buf[pos], (uint8_t *)&header, sizeof(can_header));
+    pos += sizeof(can_header);
+    memcpy(&send_buf[pos], (uint8_t *)can_data.begin(), can_data.size());
+    pos += can_data.size();
+
     if (pos >= USB_TX_SOFT_LIMIT) {
       write_func(send_buf, pos);
-      pos = 0;
+      pos = sizeof(uint32_t);
     }
   }
 
   // send remaining packets
-  if (pos > 0) write_func(send_buf, pos);
+  if (pos > sizeof(uint32_t)) write_func(send_buf, pos);
 }
 
 void Panda::can_send(capnp::List<cereal::CanData>::Reader can_data_list) {
@@ -235,20 +231,23 @@ bool Panda::can_receive(std::vector<can_frame>& out_vec) {
 
 bool Panda::unpack_can_buffer(uint8_t *data, int size, std::vector<can_frame> &out_vec) {
   recv_buf.clear();
-  for (int i = 0; i < size; i += USBPACKET_MAX_SIZE) {
-    if (data[i] != i / USBPACKET_MAX_SIZE) {
-      LOGE("CAN: MALFORMED USB RECV PACKET");
-      handle->comms_healthy = false;
-      return false;
-    }
-    int chunk_len = std::min(USBPACKET_MAX_SIZE, (size - i));
-    recv_buf.insert(recv_buf.end(), &data[i + 1], &data[i + chunk_len]);
+
+  if (size < sizeof(uint32_t)) {
+    return true;
+  }
+
+  uint32_t magic;
+  memcpy(&magic, &data[0], sizeof(uint32_t));
+  if (magic != CAN_TRANSACTION_MAGIC) {
+    LOGE("CAN: MALFORMED CAN RECV PACKET");
+    handle->comms_healthy = false;
+    return false;
   }
 
-  int pos = 0;
-  while (pos < recv_buf.size()) {
+  int pos = sizeof(uint32_t);
+  while (pos < size) {
     can_header header;
-    memcpy(&header, &recv_buf[pos], CANPACKET_HEAD_SIZE);
+    memcpy(&header, &data[pos], sizeof(can_header));
 
     can_frame &canData = out_vec.emplace_back();
     canData.busTime = 0;
@@ -262,9 +261,9 @@ bool Panda::unpack_can_buffer(uint8_t *data, int size, std::vector<can_frame> &o
     }
 
     const uint8_t data_len = dlc_to_len[header.data_len_code];
-    canData.dat.assign((char *)&recv_buf[pos + CANPACKET_HEAD_SIZE], data_len);
+    canData.dat.assign((char *)&data[pos + sizeof(can_header)], data_len);
 
-    pos += CANPACKET_HEAD_SIZE + data_len;
+    pos += sizeof(can_header) + data_len;
   }
   return true;
 }
diff --git a/selfdrive/boardd/tests/test_boardd_usbprotocol.cc b/selfdrive/boardd/tests/test_boardd_usbprotocol.cc
index c7d14fb0ef..cc3b4bce9a 100644
--- a/selfdrive/boardd/tests/test_boardd_usbprotocol.cc
+++ b/selfdrive/boardd/tests/test_boardd_usbprotocol.cc
@@ -48,7 +48,7 @@ PandaTest::PandaTest(uint32_t bus_offset_, int can_list_size, cereal::PandaState
     can.setAddress(i);
     can.setSrc(random_int(0, 3) + bus_offset);
     can.setDat(kj::ArrayPtr((uint8_t *)dat.data(), dat.size()));
-    total_pakets_size += CANPACKET_HEAD_SIZE + dat.size();
+    total_pakets_size += sizeof(can_header) + dat.size();
   }
 
   can_data_list = can_list.asReader();
@@ -58,14 +58,11 @@ PandaTest::PandaTest(uint32_t bus_offset_, int can_list_size, cereal::PandaState
 void PandaTest::test_can_send() {
   std::vector<uint8_t> unpacked_data;
   this->pack_can_buffer(can_data_list, [&](uint8_t *chunk, size_t size) {
-    int size_left = size;
-    for (int i = 0, counter = 0; i < size; i += USBPACKET_MAX_SIZE, counter++) {
-      REQUIRE(chunk[i] == counter);
-
-      const int len = std::min(USBPACKET_MAX_SIZE, size_left);
-      unpacked_data.insert(unpacked_data.end(), &chunk[i + 1], &chunk[i + len]);
-      size_left -= len;
-    }
+    uint32_t magic;
+    memcpy(&magic, &chunk[0], sizeof(uint32_t));
+
+    REQUIRE(magic == CAN_TRANSACTION_MAGIC);
+    unpacked_data.insert(unpacked_data.end(), &chunk[sizeof(uint32_t)], &chunk[size]);
   });
   REQUIRE(unpacked_data.size() == total_pakets_size);
 
@@ -73,9 +70,9 @@ void PandaTest::test_can_send() {
   INFO("test can message integrity");
   for (int pos = 0, pckt_len = 0; pos < unpacked_data.size(); pos += pckt_len) {
     can_header header;
-    memcpy(&header, &unpacked_data[pos], CANPACKET_HEAD_SIZE);
+    memcpy(&header, &unpacked_data[pos], sizeof(can_header));
     const uint8_t data_len = dlc_to_len[header.data_len_code];
-    pckt_len = CANPACKET_HEAD_SIZE + data_len;
+    pckt_len = sizeof(can_header) + data_len;
 
     REQUIRE(header.addr == cnt);
     REQUIRE(test_data.find(data_len) != test_data.end());