diff --git a/selfdrive/boardd/panda.cc b/selfdrive/boardd/panda.cc
index 75458974fc..751f735ca5 100644
--- a/selfdrive/boardd/panda.cc
+++ b/selfdrive/boardd/panda.cc
@@ -363,57 +363,49 @@ static uint8_t len_to_dlc(uint8_t len) {
   }
 }
 
-void Panda::pack_can_buffer(const capnp::List<cereal::CanData>::Reader &can_data_list,
-                         std::function<void(uint8_t *, size_t)> write_func) {
-  if (send.size() < (can_data_list.size() * CANPACKET_MAX_SIZE)) {
-    send.resize(can_data_list.size() * CANPACKET_MAX_SIZE);
+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];
   }
+}
 
-  int msg_count = 0;
-  while (msg_count < can_data_list.size()) {
-    uint32_t pos = 0;
-    while (pos < USB_TX_SOFT_LIMIT) {
-      if (msg_count == can_data_list.size()) { break; }
-      auto cmsg = can_data_list[msg_count];
-
-      // check if the message is intended for this panda
-      uint8_t bus = cmsg.getSrc();
-      if (bus < bus_offset || bus >= (bus_offset + PANDA_BUS_CNT)) {
-        msg_count++;
-        continue;
-      }
-      auto can_data = cmsg.getDat();
-      uint8_t data_len_code = len_to_dlc(can_data.size());
-      assert(can_data.size() <= ((hw_type == cereal::PandaState::PandaType::RED_PANDA) ? 64 : 8));
-      assert(can_data.size() == dlc_to_len[data_len_code]);
-
-      can_header header;
-      header.addr = cmsg.getAddress();
-      header.extended = (cmsg.getAddress() >= 0x800) ? 1 : 0;
-      header.data_len_code = data_len_code;
-      header.bus = bus - bus_offset;
-      memcpy(&send[pos], &header, CANPACKET_HEAD_SIZE);
-      memcpy(&send[pos+CANPACKET_HEAD_SIZE], can_data.begin(), can_data.size());
-
-      pos += CANPACKET_HEAD_SIZE + dlc_to_len[data_len_code];
-      msg_count++;
+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];
+
+  for (auto cmsg : can_data_list) {
+    // check if the message is intended for this panda
+    uint8_t bus = cmsg.getSrc();
+    if (bus < bus_offset || bus >= (bus_offset + PANDA_BUS_CNT)) {
+      continue;
     }
+    auto can_data = cmsg.getDat();
+    uint8_t data_len_code = len_to_dlc(can_data.size());
+    assert(can_data.size() <= ((hw_type == cereal::PandaState::PandaType::RED_PANDA) ? 64 : 8));
+    assert(can_data.size() == dlc_to_len[data_len_code]);
 
-    if (pos > 0) { // Helps not to spam with ZLP
-      // Counter needs to be inserted every 64 bytes (first byte of 64 bytes USB packet)
-      uint8_t counter = 0;
-      uint8_t to_write[USB_TX_SOFT_LIMIT+128];
-      int ptr = 0;
-      for (int i = 0; i < pos; i += 63) {
-        to_write[ptr] = counter;
-        int copy_size = ((pos - i) < 63) ? (pos - i) : 63;
-        memcpy(&to_write[ptr+1], &(send.data()[i]) , copy_size);
-        ptr += copy_size + 1;
-        counter++;
-      }
-      write_func(to_write, ptr);
+    can_header header;
+    header.addr = cmsg.getAddress();
+    header.extended = (cmsg.getAddress() >= 0x800) ? 1 : 0;
+    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());
+    if (pos >= USB_TX_SOFT_LIMIT) {
+      write_func(send_buf, pos);
+      pos = 0;
     }
   }
+
+  // send remaining packets
+  if (pos > 0) write_func(send_buf, pos);
 }
 
 void Panda::can_send(capnp::List<cereal::CanData>::Reader can_data_list) {
diff --git a/selfdrive/boardd/panda.h b/selfdrive/boardd/panda.h
index 79124a59b1..fe69189489 100644
--- a/selfdrive/boardd/panda.h
+++ b/selfdrive/boardd/panda.h
@@ -69,7 +69,6 @@ class Panda {
   libusb_context *ctx = NULL;
   libusb_device_handle *dev_handle = NULL;
   std::mutex usb_lock;
-  std::vector<uint8_t> send;
   std::vector<uint8_t> recv_buf;
   void handle_usb_issue(int err, const char func[]);
   void cleanup();