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1538 killagreg 1
// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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// This code has been derived from the implementation of Stefan Engelke.
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// ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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/*
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    Copyright (c) 2008 Stefan Engelke <stefan@tinkerer.eu>
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    Permission is hereby granted, free of charge, to any person
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    obtaining a copy of this software and associated documentation
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    files (the "Software"), to deal in the Software without
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    restriction, including without limitation the rights to use, copy,
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    modify, merge, publish, distribute, sublicense, and/or sell copies
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    of the Software, and to permit persons to whom the Software is
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    furnished to do so, subject to the following conditions:
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    The above copyright notice and this permission notice shall be
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    included in all copies or substantial portions of the Software.
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    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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    HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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    WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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    DEALINGS IN THE SOFTWARE.
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    $Id: rcdsl.c 60 2008-08-21 07:50:48Z taser $
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    RCDSL.H and RCDSL.C is an INOFFICIAL implementation of the
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    communication protocol used by DSL receivers of Act Europe.
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    The DSL receivers have a serial communication port to connect
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    two receivers in diversity mode. Each receiver is sending the
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    received servo signals periodically over this port. This fact
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    can be used to connect the receiver to the control unit of the
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    model via UART instead of evaluating the PPM signal.
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    If you have any questions, fell free to send me an e-mail.
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*/
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/*
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Connection of DSL to SV1 of FC:
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( DSL Pin1 is on side of channel 4 )
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1. GND <--> pin 7 (GND)
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2. TXD <--> pin 3 (RXD1 Atmega644p)
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3. RXD <--> pin 4 (TXD1 Atmega644p) optional
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4. 5V  <--> pin 2 (5V)
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If a receiver is connected via PPM input at the same time, the PPM input will be disabled
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if a stable signal can be captured by the uart.
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Data are send at every 20 ms @ 38400 Baud 8-N-1
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Data Frame: |0xFF|0xFF|0x1F|FREQALLOC|??|RSSI|VBAT|??|CRC|10|CH0D1|CH0D0|CH1D1|CH1D0|CRC| ...etc
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FREQALLOC = 35, 40, 72
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RSSI = 0.. 255 // Received signal strength indicator
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VBAT = 0...255 // supply voltage (0.0V.. 7.8V)
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Servo Pair:   |0x1X|CHXD1|CHXD0|CHX+1D1|CHX+1D0|CRC|
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X is channel index of 1 servo value
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D1D0 is servo value as u16 in range of 7373 (1ms) to 14745 (2ms)
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there are 8 channels submitted, i.e 4 servo pairs
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Frame examples with signel received
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FFFF 1F23F079A304AD 1036012B1E6F 122AFB2AECB2 142B4D2B4404 1636872B33CE
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FFFF 1F23F079A304AD 1036002B1F6F 122AFE2AEBB0 142B4B2B4406 1636872B33CE
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FFFF 1F23F079A304AD 1035FF2B226E 122AFC2AEAB3 142B4E2B4304 1636882B33CD
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FFFF 1F23F079A304AD 1036022B1E6E 122AFB2AEEB0 142B4A2B4506 1636872B33CE
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FFFF 1F23F079A304AD 1036022B1E6E 122AFE2AEBB0 142B4B2B4406 1636882B33CD
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FFFF 1F23F079A304AD 1036012B1E6F 122AFD2AEAB2 142B4E2B4403 1636862B33CF
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FFFF 1F23F079A304AD 1036032B1D6E 122AFD2AEBB1 142B4C2B4504 1636862B33CF
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Frame examples with no signal received
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FFFF 1F23F000A30426
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FFFF 1F23F000A30426
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FFFF 1F23F000A30426
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FFFF 1F23F000A30426
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FFFF 1F23F000A30426
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FFFF 1F23F000A30426
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FFFF 1F23F000A30426
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*/
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#include <stdlib.h>
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#include "dsl.h"
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#include "rc.h"
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#include "eeprom.h"
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uint8_t dsl_RSSI = 0;
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uint8_t dsl_Battery = 0;
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uint8_t dsl_Allocation = 0;
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uint8_t PacketBuffer[6];
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typedef union
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{
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        int16_t Servo[2];
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        uint8_t  byte[4];
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} ChannelPair_t;
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ChannelPair_t ChannelPair;
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// This function is called, when a new servo signal is properly received.
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// Parameters: servo  - servo number (0-9)
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//             signal - servo signal between 7373 (1ms) and 14745 (2ms)
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void dsl_new_signal(uint8_t channel, int16_t signal)
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{
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    int16_t tmp;
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    uint8_t index = channel + 1; // mk channels start with 1
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        if(index > 0  &&  index < MAX_CHANNELS)
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        {
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                if(RC_Channels < index)  RC_Channels = index;
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                // signal from  DSL-receiver is between 7373 (1ms) und 14745 (2ms).
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                signal-= 11059;     // shift to neutral
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                signal/= 24;        // scale to mk rc resolution
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                if(abs(signal - PPM_in[index]) < 6)
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                {
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                        if(RC_Quality < 200)
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                        {
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                                RC_Quality += 10;
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                        }
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                        else
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                        {
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                                RC_Quality = 200;
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                                PPM_INPUT_OFF; // disable PPM input at ICP
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                        }
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                }
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                // calculate exponential history for signal
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                tmp = (3 * (PPM_in[index]) + signal) / 4;
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                if(tmp > signal+1) tmp--;
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                else if(tmp < signal-1) tmp++;
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                // calculate signal difference on good signal level
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                if(RC_Quality >= 180)  PPM_diff[index] = ((tmp - PPM_in[index]) / 3) * 3; // cut off lower 3 bit for noise reduction
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                else PPM_diff[index] = 0;
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                PPM_in[index] = tmp; // update channel value
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                if(index == 4)
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                {
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                        NewPpmData = 0;
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                }
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        }
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}
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// This function is called within dsl_parser(), when a complete
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// data packet with valid checksum has been received.
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void dsl_decode_packet(void)
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{
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    uint8_t  i;
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        // check for header condition
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        if((PacketBuffer[0] & 0xF0) == 0x10)
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        {
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                if(PacketBuffer[0] == 0x1F) // separate status frame
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                {
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                        dsl_Allocation  = PacketBuffer[1]; // Get frequency allocation
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                        // ??                   = PacketBuffer[2];
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                        dsl_RSSI                = PacketBuffer[3]; // Get signal quality
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                        dsl_Battery     = PacketBuffer[4]; // Get voltage of battery supply
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                        // ??                   = PacketBuffer[5];
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                        RC_RSSI                 = dsl_RSSI;
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                        PPM_in[0] = RC_RSSI;
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                        if(RC_RSSI == 0)
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                        {   // set to neutral attitude commands
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                                PPM_diff[ParamSet.ChannelAssignment[CH_NICK]] = 0;
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                                PPM_diff[ParamSet.ChannelAssignment[CH_ROLL]] = 0;
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                                PPM_diff[ParamSet.ChannelAssignment[CH_YAW]]  = 0;
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                                PPM_in[ParamSet.ChannelAssignment[CH_NICK]] = 0;
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                                PPM_in[ParamSet.ChannelAssignment[CH_ROLL]] = 0;
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                                PPM_in[ParamSet.ChannelAssignment[CH_YAW]]  = 0;
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                        }
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                }
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                else // probably a channel pair
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                {
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                        i = PacketBuffer[0] & 0x0F;   // last 4 bits of the header indicates the channel pair
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                        if(i < 10)// maximum 12 channels
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                        {
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                                // big to little endian
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                                ChannelPair.byte[1] = PacketBuffer[1];
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                                ChannelPair.byte[0] = PacketBuffer[2];
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                                ChannelPair.byte[3] = PacketBuffer[3];
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                                ChannelPair.byte[2] = PacketBuffer[4];
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                                dsl_new_signal(i,  ChannelPair.Servo[0]);
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                                dsl_new_signal(i+1,ChannelPair.Servo[1]);
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                        }
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                }
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        } // EOF header condition
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}
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// this function should be called within the UART RX ISR
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void dsl_parser(uint8_t c)
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{
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        static uint8_t last_c = 0;
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        static uint8_t crc      = 0;
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        static uint8_t cnt = 0;
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        static uint8_t packet_len = 0;
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        // check for sync condition
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        if ((c==0xFF) && (last_c==0xFF))
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        {
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                cnt = 0; // reset byte counter
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                crc = 0; // reset checksum
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                return;
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    }
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        if(cnt == 0) // begin of a packet
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        {
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                if(c == 0x1F)   packet_len = 5; // a status packet has 5 bytes + crc
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                else                    packet_len = 4; // a channel pair packet has 4 bytes + crc
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        }
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        if(cnt > packet_len) // packet complete, crc byte received
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        {
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                // calculate checksum
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                crc = ~crc;
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                if (crc == 0xFF) crc = 0xFE;
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                // if crc matches decode the packet
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        if (c == crc) dsl_decode_packet();
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        // handle next packet
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        cnt = 0;
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        crc = 0;
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        }
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        else // collect channel data bytes
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        {
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                PacketBuffer[cnt++] = c;
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                crc += c;
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        }
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        // store last byte for sync check
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        last_c = c;
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}