1
0
mirror of https://github.com/f4exb/sdrangel.git synced 2024-11-05 08:21:16 -05:00
sdrangel/plugins/channelrx/demodendoftrain/endoftrainpacket.cpp
2024-03-03 13:40:42 +00:00

100 lines
3.8 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2024 Jon Beniston, M7RCE <jon@beniston.com> //
// Copyright (C) 2018 Eric Reuter //
// //
// 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 "endoftrainpacket.h"
#include "util/crc.h"
// Reverse order of bits
static quint32 reverse(quint32 x)
{
x = (((x & 0xaaaaaaaa) >> 1) | ((x & 0x55555555) << 1));
x = (((x & 0xcccccccc) >> 2) | ((x & 0x33333333) << 2));
x = (((x & 0xf0f0f0f0) >> 4) | ((x & 0x0f0f0f0f) << 4));
x = (((x & 0xff00ff00) >> 8) | ((x & 0x00ff00ff) << 8));
return((x >> 16) | (x << 16));
}
// Reverse order of bits, for specified number of bits
static quint32 reverseBits(quint32 x, int bits)
{
return reverse(x) >> (32-bits);
}
// Decode end-of-train packet
// Defined in:
// AAR MSRP (Manual of Standards and Recommended Practices) - Section K Part II Locomotive Electronics and Train Consist System Architecture - S-9152 End of Train Communication
// but not readily available, so see:
// https://patents.google.com/patent/US5374015A/en
// https://rdso.indianrailways.gov.in/uploads/files/TC0156_15_02_2022.pdf
bool EndOfTrainPacket::decode(const QByteArray& packet)
{
//qDebug() << packet.toHex();
if (packet.size() != 8) {
return false;
}
m_chainingBits = packet[0] & 0x3;
m_batteryCondition = (packet[0] >> 2) & 0x3;
m_type = (packet[0] >> 4) & 0x7;
m_address = ((packet[2] & 0xff) << 9) | ((packet[1] & 0xff) << 1) | ((packet[0] >> 7) & 0x1);
m_pressure = packet[3] & 0x7f;
m_discretionary = (packet[3] >> 7) & 1;
m_batteryCharge = packet[4] & 0x7f;
m_valveCircuitStatus = (packet[4] >> 7) & 1;
m_confirmation = packet[5] & 1;
m_turbine = (packet[5] >> 1) & 1;
m_motion = (packet[5] >> 2) & 1;
m_markerLightBatteryCondition = (packet[5] >> 3) & 1;
m_markerLightStatus = (packet[5] >> 4) & 1;
// Calculate and compare CRC
crc crc18(18, 0x39A0F, true, 0, 0x2b770);
// 45-bits are protected
crc18.calculate(packet[5] & 0x1f, 5);
crc18.calculate(packet[4] & 0xff, 8);
crc18.calculate(packet[3] & 0xff, 8);
crc18.calculate(packet[2] & 0xff, 8);
crc18.calculate(packet[1] & 0xff, 8);
crc18.calculate(packet[0] & 0xff, 8);
m_crc = ((packet[7] & 0xff) << 11) | ((packet[6] & 0xff) << 3) | ((packet[5] >> 5) & 0x7);
m_crcCalculated = reverseBits(crc18.get(), 18);
m_crcValid = m_crc == m_crcCalculated;
if (crc18.get() != m_crc) {
qDebug() << "CRC Mismatch: " << QString::number(crc18.get(), 16) << QString::number(m_crc, 16);
}
m_dataHex = QString(packet.toHex());
return m_crcValid;
}