From 7102205be3f20739bf55eb42c4177305f881fed0 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Fri, 1 Dec 2023 09:00:05 +1100
Subject: [PATCH] AP_Math: added crc_sum_of_bytes_16()

---
 libraries/AP_Math/crc.cpp | 14 ++++++++++----
 libraries/AP_Math/crc.h   |  5 ++++-
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/libraries/AP_Math/crc.cpp b/libraries/AP_Math/crc.cpp
index 985a02c290..de81543b48 100644
--- a/libraries/AP_Math/crc.cpp
+++ b/libraries/AP_Math/crc.cpp
@@ -599,13 +599,19 @@ uint8_t parity(uint8_t byte)
     return p;
 }
 
-// sums the bytes in the supplied buffer, returns that sum mod 256
-// (i.e. shoved into a uint8_t)
-uint8_t crc_sum_of_bytes(uint8_t *data, uint16_t count)
+// sums the bytes in the supplied buffer, returns that sum mod 0xFFFF
+uint16_t crc_sum_of_bytes_16(const uint8_t *data, uint16_t count)
 {
-    uint8_t ret = 0;
+    uint16_t ret = 0;
     for (uint32_t i=0; i<count; i++) {
         ret += data[i];
     }
     return ret;
 }
+
+// sums the bytes in the supplied buffer, returns that sum mod 256
+// (i.e. shoved into a uint8_t)
+uint8_t crc_sum_of_bytes(const uint8_t *data, uint16_t count)
+{
+    return crc_sum_of_bytes_16(data, count) & 0xFF;
+}
diff --git a/libraries/AP_Math/crc.h b/libraries/AP_Math/crc.h
index e0c024bc15..5aa39e70a8 100644
--- a/libraries/AP_Math/crc.h
+++ b/libraries/AP_Math/crc.h
@@ -66,4 +66,7 @@ uint8_t parity(uint8_t byte);
 
 // sums the bytes in the supplied buffer, returns that sum mod 256
 // (i.e. shoved into a uint8_t)
-uint8_t crc_sum_of_bytes(uint8_t *data, uint16_t count);
+uint8_t crc_sum_of_bytes(const uint8_t *data, uint16_t count);
+
+// sums the bytes in the supplied buffer, returns that sum mod 0xFFFF
+uint16_t crc_sum_of_bytes_16(const uint8_t *data, uint16_t count);