openpilot support for panda nak (#1324)

panda

@@ -1 +1 @@
-Subproject commit 51e0a55d6d5fce5a9edf4178baccd4b2a4e23290
+Subproject commit 5440de0fdee3f04a1b1a15291854d2a183af5f67

selfdrive/boardd/boardd.cc

@@ -568,10 +568,19 @@ void can_send(SubSocket *subscriber) {
   int sent;
   pthread_mutex_lock(&usb_lock);
 
+
   if (!fake_send) {
     do {
-      err = libusb_bulk_transfer(dev_handle, 3, (uint8_t*)send, msg_count*0x10, &sent, TIMEOUT);
-      if (err != 0 || msg_count*0x10 != sent) { handle_usb_issue(err, __func__); }
+      // Try sending can messages. If the receive buffer on the panda is full it will NAK
+      // and libusb will try again. After 5ms, it will time out. We will drop the messages.
+      err = libusb_bulk_transfer(dev_handle, 3, (uint8_t*)send, msg_count*0x10, &sent, 5);
+      if (err == LIBUSB_ERROR_TIMEOUT) {
+        LOGW("Transmit buffer full");
+        break;
+      } else if (err != 0 || msg_count*0x10 != sent) {
+        LOGW("Error");
+        handle_usb_issue(err, __func__);
+      }
     } while(err != 0);
   }