From 041f09896ab095ce1d36f2f40e7280e9cac1bab3 Mon Sep 17 00:00:00 2001
From: Matt Way <mattyway@gmail.com>
Date: Sat, 9 Dec 2023 09:57:11 +1100
Subject: [PATCH] Use PacketCRC helper

---
 HDPacketBuilder.h | 27 +++++--------------------
 PacketCRC.cpp     | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 PacketCRC.h       | 18 +++++++++++++++++
 3 files changed, 74 insertions(+), 22 deletions(-)
 create mode 100644 PacketCRC.cpp
 create mode 100644 PacketCRC.h

diff --git a/HDPacketBuilder.h b/HDPacketBuilder.h
index 695bbf8..d1e2360 100644
--- a/HDPacketBuilder.h
+++ b/HDPacketBuilder.h
@@ -1,4 +1,4 @@
-#include <CRC16.h>
+#include "PacketCRC.h"
 
 #define LENGTH_17                      (0x11)
 #define LENGTH_21                      (0x15)
@@ -15,7 +15,7 @@ uint8_t rollingCode2 = 0x82;
 
 uint8_t buf[32];
 
-CRC16 crc(0x755B, 0x0, 0xBA68, false, false);
+PacketCRC packetCRC;
 
 void setPacketLength(uint8_t);
 void setConstants();
@@ -140,26 +140,9 @@ void setProtocolVersion(uint8_t version) {
 }
 
 void calculateCRC() { // must be called after the buffer has been filled
-  crc.restart();
-  uint8_t length = buf[0];
-  switch(length) {
-    case 0x11:
-      crc.setXorOut(0xBA68);
-      break;
-    case 0x15:
-      crc.setXorOut(0xE10C);
-      break;
-    case 0x19:
-      crc.setXorOut(0x89A0);
-      break;
-    default:
-      Serial.print("Unsupported length (");
-      Serial.print(length);
-      Serial.println("). Cannot calculate CRC");
-      return;
-  }
-  crc.add(buf, length + 1);
-  uint16_t result = crc.calc();
+  uint8_t length = buf[1];
+  uint16_t result = packetCRC.calculate(buf);
+
   uint8_t checksum1 = (uint8_t)((result & 0xFF00) >> 8);
   uint8_t checksum2 = (uint8_t)(result & 0x00FF);
 
diff --git a/PacketCRC.cpp b/PacketCRC.cpp
new file mode 100644
index 0000000..e3ef255
--- /dev/null
+++ b/PacketCRC.cpp
@@ -0,0 +1,51 @@
+#include "PacketCRC.h"
+
+PacketCRC::PacketCRC() : crc(CRC16(0x755B, 0x0, 0xBA68, false, false)) {
+  // Constructor implementation (if needed)
+}
+
+PacketCRC::~PacketCRC() {
+  // Destructor implementation (if needed)
+}
+
+bool PacketCRC::check(const uint8_t* packet) {
+  uint8_t length = packet[1];
+  switch(length) {
+    case 0x11:
+    case 0x15:
+    case 0x19:
+      break;
+    default:
+      return false;
+  }
+
+  uint16_t result = calculate(packet);
+  uint8_t checksum1 = (uint8_t)((result & 0xFF00) >> 8);
+  uint8_t checksum2 = (uint8_t)(result & 0x00FF);
+
+  if (packet[length + 2] == checksum1 && packet[length + 3] == checksum2) {
+    return true;
+  }
+
+  return false;
+}
+
+uint16_t PacketCRC::calculate(const uint8_t* packet) {
+  crc.restart();
+  uint8_t length = packet[1];
+  switch(length) {
+    case 0x11:
+      crc.setXorOut(0x539E);
+      break;
+    case 0x15:
+      crc.setXorOut(0x3B0E);
+      break;
+    case 0x19:
+      crc.setXorOut(0x5C02);
+      break;
+    default:
+      return 0x0000;
+  }
+  crc.add(packet, length + 2);
+  return crc.calc();
+}
\ No newline at end of file
diff --git a/PacketCRC.h b/PacketCRC.h
new file mode 100644
index 0000000..e5d5512
--- /dev/null
+++ b/PacketCRC.h
@@ -0,0 +1,18 @@
+#ifndef PACKET_CRC_H
+#define PACKET_CRC_H
+
+#include <CRC16.h>
+
+class PacketCRC {
+public:
+    PacketCRC();
+    ~PacketCRC();
+
+    // Method to calculate CRC for a packet
+    bool check(const uint8_t* packet);
+    uint16_t calculate(const uint8_t* packet);
+private:
+    CRC16 crc;
+};
+
+#endif // PACKET_CRC_H
\ No newline at end of file