Add packet modulator for transmitting packet radio data packets (AX.25/APRS)

2026-07-25 19:44:12 -04:00 · 2020-09-18 16:36:27 +01:00
parent 27ac574db8
commit 2b48e969ba
55 changed files with 6931 additions and 15 deletions
@@ -0,0 +1,61 @@
+///////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2020 Jon Beniston, M7RCE                                        //
+//                                                                               //
+// This program 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 as version 3 of the License, or                  //
+// (at your option) any later version.                                           //
+//                                                                               //
+// This program 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 V3 for more details.                               //
+//                                                                               //
+// You should have received a copy of the GNU General Public License             //
+// along with this program. If not, see <http://www.gnu.org/licenses/>.          //
+///////////////////////////////////////////////////////////////////////////////////
+
+#include "crc.h"
+#include "QDebug.h"
+
+// Reverse bit ordering
+uint32_t crc::reverse(uint32_t val, int bits)
+{
+    uint32_t temp;
+    int i;
+
+    temp = 0;
+    for (i = 0; i < bits; i++)
+        temp |= ((val >> i) & 1) << (bits - 1 - i);
+    return temp;
+}
+
+// Calculate CRC for specified number of bits
+void crc::calculate(uint32_t data, int data_bits)
+{
+    uint32_t tmp;
+    uint32_t mask;
+    int bit, i;
+
+    // Reverse data order.
+    if (m_msb_first)
+        data = reverse (data, data_bits);
+
+    // Compute CRC.
+    tmp = m_crc;
+    for (i = 0; i < data_bits; i++) {
+        bit = ((data >> i) & 1) ^ (tmp & 1);
+        if (bit)
+            tmp = (tmp >> 1) ^ m_polynomial_rev;
+        else
+            tmp = tmp >> 1;
+    }
+    m_crc = tmp;
+}
+
+// Calculate CRC for specified array
+void crc::calculate(const uint8_t *data, int length)
+{
+    for(int i = 0; i < length; i++)
+        calculate(data[i], 8);
+}