Import grbl v1.1h
diff --git a/grbl/serial.h b/grbl/serial.h
new file mode 100644
index 0000000..5a3f776
--- /dev/null
+++ b/grbl/serial.h
@@ -0,0 +1,62 @@
+/*
+ serial.c - Low level functions for sending and recieving bytes via the serial port
+ Part of Grbl
+
+ Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
+ Copyright (c) 2009-2011 Simen Svale Skogsrud
+
+ Grbl is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ Grbl is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Grbl. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef serial_h
+#define serial_h
+
+
+#ifndef RX_BUFFER_SIZE
+ #define RX_BUFFER_SIZE 128
+#endif
+#ifndef TX_BUFFER_SIZE
+ #ifdef USE_LINE_NUMBERS
+ #define TX_BUFFER_SIZE 112
+ #else
+ #define TX_BUFFER_SIZE 104
+ #endif
+#endif
+
+#define SERIAL_NO_DATA 0xff
+
+
+void serial_init();
+
+// Writes one byte to the TX serial buffer. Called by main program.
+void serial_write(uint8_t data);
+
+// Fetches the first byte in the serial read buffer. Called by main program.
+uint8_t serial_read();
+
+// Reset and empty data in read buffer. Used by e-stop and reset.
+void serial_reset_read_buffer();
+
+// Returns the number of bytes available in the RX serial buffer.
+uint8_t serial_get_rx_buffer_available();
+
+// Returns the number of bytes used in the RX serial buffer.
+// NOTE: Deprecated. Not used unless classic status reports are enabled in config.h.
+uint8_t serial_get_rx_buffer_count();
+
+// Returns the number of bytes used in the TX serial buffer.
+// NOTE: Not used except for debugging and ensuring no TX bottlenecks.
+uint8_t serial_get_tx_buffer_count();
+
+#endif