From 4b954f39544aed4e7d2f2633ac87b14f128f21bf Mon Sep 17 00:00:00 2001
From: df8oe <df8oe@gmx.de>
Date: Fri, 9 Jun 2017 18:51:06 +0200
Subject: [PATCH] fixed missing function

---
 main.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/main.c b/main.c
index 5b13fa1..339138f 100644
--- a/main.c
+++ b/main.c
@@ -233,6 +233,22 @@ void send_rtty_packet() {
   send_cun++;
 }
 
+uint16_t gps_CRC16_checksum(char *string) {
+  uint16_t crc = 0xffff;
+  char i;
+  while (*(string) != 0) {
+    crc = crc ^ (*(string++) << 8);
+    for (i = 0; i < 8; i++) {
+      if (crc & 0x8000)
+        crc = (uint16_t) ((crc << 1) ^ 0x1021);
+      else
+        crc <<= 1;
+    }
+  }
+  return crc;
+}
+
+
 #ifdef  DEBUG
 void assert_failed(uint8_t* file, uint32_t line)
 {