diff --git a/libraries/AP_Math/crc.cpp b/libraries/AP_Math/crc.cpp
index 6ab0612317..b57227d779 100644
--- a/libraries/AP_Math/crc.cpp
+++ b/libraries/AP_Math/crc.cpp
@@ -334,3 +334,16 @@ uint32_t crc_crc24(const uint8_t *bytes, uint16_t len)
     }
     return crc;
 }
+
+// simple 8 bit checksum used by FPort
+uint8_t crc_sum8(const uint8_t *p, uint8_t len)
+{
+    uint16_t sum = 0;
+    for (uint8_t i=0; i<len; i++) {
+        sum += p[i];
+        sum += sum >> 8;
+        sum &= 0xFF;              
+    }
+    sum = 0xff - ((sum & 0xff) + (sum >> 8));
+    return sum;
+}
diff --git a/libraries/AP_Math/crc.h b/libraries/AP_Math/crc.h
index e80eb77363..bf000cadcd 100644
--- a/libraries/AP_Math/crc.h
+++ b/libraries/AP_Math/crc.h
@@ -28,6 +28,9 @@ uint32_t crc_crc32(uint32_t crc, const uint8_t *buf, uint32_t size);
 uint32_t crc32_small(uint32_t crc, const uint8_t *buf, uint32_t size);
 uint32_t crc_crc24(const uint8_t *bytes, uint16_t len);
 
+// checksum used by SPORT/FPort
+uint8_t crc_sum8(const uint8_t *p, uint8_t len);
+
 // Copyright (C) 2010 Swift Navigation Inc.
 // Contact: Fergus Noble <fergus@swift-nav.com>
 uint16_t crc16_ccitt(const uint8_t *buf, uint32_t len, uint16_t crc);