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#include "dsl.h"
#include "rc.h"
/*
Connection of DSL to SV1 of FC:
( DSL Pin1 is on side of channel 4 )
1. GND <--> pin 7 (GND)
2. TXD <--> pin 3 (RXD1 Atmega644p)
3. RXD <--> pin 4 (TXD1 Atmega644p) optional
4. 5V <--> pin 2 (5V)
Do not connect the receiver via PPM-Sumsignal output the same time.
Data are send at 38400baud8n1
Data Frame: |0xFF|0xFF|0x1F|FREQALLOC|??|RSSI|VBAT|??|CRC|10|CH0D1|CH0D0|CH1D1|CH1D0|CRC| ...etc
FREQALLOC = 35, 40, 72
RSSI = 0.. 255 // Received signal strength indicator
VBAT = 0...255 // supply voltage (0.0V.. 8.2V)
Servo Pair: |0x1X|CHXD1|CHXD0|CHX+1D1|CHX+1D0|CRC|
X is channel index of 1 servo value
D1D0 is servo value as u16 in range of 7373 (1ms) to 14745 (2ms)
there are 8 channels submitted, i.e 4 servo pairs
Frame examples with signel received
FFFF 1F23F079A304AD 1036012B1E6F 122AFB2AECB2 142B4D2B4404 1636872B33CE
FFFF 1F23F079A304AD 1036002B1F6F 122AFE2AEBB0 142B4B2B4406 1636872B33CE
FFFF 1F23F079A304AD 1035FF2B226E 122AFC2AEAB3 142B4E2B4304 1636882B33CD
FFFF 1F23F079A304AD 1036022B1E6E 122AFB2AEEB0 142B4A2B4506 1636872B33CE
FFFF 1F23F079A304AD 1036022B1E6E 122AFE2AEBB0 142B4B2B4406 1636882B33CD
FFFF 1F23F079A304AD 1036012B1E6F 122AFD2AEAB2 142B4E2B4403 1636862B33CF
FFFF 1F23F079A304AD 1036032B1D6E 122AFD2AEBB1 142B4C2B4504 1636862B33CF
Frame examples with no signal received
FFFF 1F23F000A30426
FFFF 1F23F000A30426
FFFF 1F23F000A30426
FFFF 1F23F000A30426
FFFF 1F23F000A30426
FFFF 1F23F000A30426
FFFF 1F23F000A30426
*/
uint8_t dsl_RSSI = 0;
uint8_t dsl_Battery = 0;
uint8_t dsl_Allocation = 0;
uint8_t PacketBuffer[6];
typedef union
{
int16_t Servo[2];
uint8_t byte[4];
} ChannelPair_t;
ChannelPair_t ChannelPair;
// This function is called, when a new servo signal is properly received.
// Parameters: servo - servo number (0-9)
// signal - servo signal between 7373 (1ms) and 14745 (2ms)
void dsl_new_signal(uint8_t channel, int16_t signal)
{
int16_t tmp;
uint8_t index = channel + 1; // mk channels start with 1
// signal from DSL-receiver is between 7373 (1ms) und 14745 (2ms).
signal-= 11059; // shift to neutral
signal/= 24; // scale to mk rc resolution
// calculate exponential history for signal
tmp = (3 * (PPM_in[index]) + signal) / 4;
if(tmp > signal+1) tmp--; else
if(tmp < signal-1) tmp++;
// calculate signal difference on good signal level
if(RC_Quality >= 195) PPM_diff[index] = ((tmp - PPM_in[index]) / 3) * 3; // cut off lower 3 bit for noise reduction
else PPM_diff[index] = 0;
PPM_in[index] = tmp; // update channel value
if(index == 4)
{
NewPpmData = 0;
NewRCFrames++;
}
}
// This function is called within dsl_parser(), when a complete
// data packet with valid checksum has been received.
void dsl_decode_packet(void)
{
uint8_t i;
// check for header condition
if((PacketBuffer[0] & 0xF0) == 0x10)
{
if(PacketBuffer[0] == 0x1F) // separate status frame
{
dsl_Allocation = PacketBuffer[1]; // Get frequency allocation
// ?? = PacketBuffer[2];
dsl_RSSI = PacketBuffer[3]; // Get signal quality
RC_Quality = (212 * (uint16_t)dsl_RSSI) / 128; // have to be scaled approx. by a factor of 1.66 to get 200 at full level
if(RC_Quality > 255) RC_Quality = 255;
dsl_Battery = PacketBuffer[4]; // Get voltage of battery supply
// ?? = PacketBuffer[5];
if(dsl_RSSI == 0)
{
for (i = 0; i<5; i++)
{
PPM_diff[i] = 0;
PPM_in[i] = 0;
}
}
}
else // probably a channel pair
{
i = PacketBuffer[0] & 0x0F; // last 4 bits of the header indicates the channel pair
if(i < 10)// maximum 12 channels
{
// big to little endian
ChannelPair.byte[1] = PacketBuffer[1];
ChannelPair.byte[0] = PacketBuffer[2];
ChannelPair.byte[3] = PacketBuffer[3];
ChannelPair.byte[2] = PacketBuffer[4];
dsl_new_signal(i, ChannelPair.Servo[0]);
dsl_new_signal(i+1,ChannelPair.Servo[1]);
}
}
} // EOF header condition
}
// this function should be called within the UART RX ISR
void dsl_parser(uint8_t c)
{
static uint8_t last_c = 0;
static uint8_t crc = 0;
static uint8_t cnt = 0;
static uint8_t packet_len = 0;
// check for sync condition
if ((c==0xFF) && (last_c==0xFF))
{
cnt = 0; // reset byte counter
crc = 0; // reset checksum
return;
}
if(cnt == 0) // begin of a packet
{
if(c == 0x1F) packet_len = 5; // a status packet has 5 bytes + crc
else packet_len = 4; // a channel pair packet has 4 bytes + crc
}
if(cnt > packet_len) // packet complete, crc byte received
{
// calculate checksum
crc = ~crc;
if (crc == 0xFF) crc = 0xFE;
// if crc matches decode the packet
if (c == crc) dsl_decode_packet();
// handle next packet
cnt = 0;
crc = 0;
}
else // collect channel data bytes
{
PacketBuffer[cnt++] = c;
crc += c;
}
// store last byte for sync check
last_c = c;
}