diff --git a/grc/CMakeLists.txt b/grc/CMakeLists.txt
index c260c62..e76e60c 100644
--- a/grc/CMakeLists.txt
+++ b/grc/CMakeLists.txt
@@ -33,5 +33,6 @@ install(FILES
satnogs_frame_encoder.xml
satnogs_doppler_correction_cc.xml
satnogs_upsat_fsk_frame_acquisition.xml
- satnogs_upsat_fsk_frame_encoder.xml DESTINATION share/gnuradio/grc/blocks
+ satnogs_upsat_fsk_frame_encoder.xml
+ satnogs_whitening.xml DESTINATION share/gnuradio/grc/blocks
)
diff --git a/grc/satnogs_whitening.xml b/grc/satnogs_whitening.xml
new file mode 100644
index 0000000..66815b7
--- /dev/null
+++ b/grc/satnogs_whitening.xml
@@ -0,0 +1,38 @@
+
+
+ whitening
+ satnogs_whitening
+ satnogs
+ import satnogs
+ satnogs.whitening($mask, $seed, $order)
+
+
+ ...
+ ...
+ ...
+
+
+
+
+ in
+
+
+
+
+
+ out
+
+
+
diff --git a/include/satnogs/CMakeLists.txt b/include/satnogs/CMakeLists.txt
index 32e4a5d..802df56 100644
--- a/include/satnogs/CMakeLists.txt
+++ b/include/satnogs/CMakeLists.txt
@@ -46,5 +46,6 @@ install(FILES
doppler_fit.h
freq_drift.h
upsat_fsk_frame_acquisition.h
- upsat_fsk_frame_encoder.h DESTINATION include/satnogs
+ upsat_fsk_frame_encoder.h
+ whitening.h DESTINATION include/satnogs
)
diff --git a/include/satnogs/whitening.h b/include/satnogs/whitening.h
new file mode 100644
index 0000000..e68117f
--- /dev/null
+++ b/include/satnogs/whitening.h
@@ -0,0 +1,57 @@
+/* -*- c++ -*- */
+/*
+ * gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
+ *
+ * Copyright (C) 2016, Libre Space Foundation
+ *
+ * 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, either 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 for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see .
+ */
+
+#ifndef INCLUDED_SATNOGS_WHITENING_H
+#define INCLUDED_SATNOGS_WHITENING_H
+
+#include
+
+namespace gr
+{
+ namespace satnogs
+ {
+
+ /*!
+ * \brief Performs data whitening and de-whitening
+ *
+ */
+ class SATNOGS_API whitening
+ {
+ public:
+ whitening (uint32_t mask, uint32_t seed, uint32_t order);
+ ~whitening ();
+
+ void
+ reset();
+
+ void scramble(uint8_t *out, const uint8_t *in, size_t len);
+ void descramble(uint8_t *out, const uint8_t *in, size_t len);
+
+ private:
+ const size_t d_lut_len;
+ size_t d_lut_idx;
+ uint8_t *d_lut;
+ };
+
+ } // namespace satnogs
+} // namespace gr
+
+#endif /* INCLUDED_SATNOGS_WHITENING_H */
+
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index d7e88bb..870bf06 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -44,7 +44,8 @@ list(APPEND satnogs_sources
doppler_fit.cc
freq_drift.cc
upsat_fsk_frame_acquisition_impl.cc
- upsat_fsk_frame_encoder_impl.cc )
+ upsat_fsk_frame_encoder_impl.cc
+ whitening.cc )
set(satnogs_sources "${satnogs_sources}" PARENT_SCOPE)
if(NOT satnogs_sources)
diff --git a/lib/upsat_fsk_frame_acquisition_impl.cc b/lib/upsat_fsk_frame_acquisition_impl.cc
index bea3176..c150e1e 100644
--- a/lib/upsat_fsk_frame_acquisition_impl.cc
+++ b/lib/upsat_fsk_frame_acquisition_impl.cc
@@ -72,7 +72,8 @@ namespace gr
d_shifting_byte (0x0),
d_decoded_bytes (0),
d_decoded_bits (0),
- d_frame_len (0)
+ d_frame_len (0),
+ d_descrambler(0x21, 0x1FF, 9)
{
size_t i;
message_port_register_out (pmt::mp ("pdu"));
@@ -154,6 +155,7 @@ namespace gr
upsat_fsk_frame_acquisition_impl::have_frame_len ()
{
LOG_DEBUG("Enter frame len");
+ d_descrambler.reset();
d_state = HAVE_FRAME_LEN;
d_decoded_bytes = 0;
d_decoded_bits = 0;
@@ -243,10 +245,20 @@ namespace gr
case HAVE_FRAME_LEN:
d_decoded_bits++;
if(d_decoded_bits == 8) {
- /* Frame length field is needed for the CRC calculation */
- d_pdu[0] = d_shifting_byte;
- /* CRC is not included in the frame length field, but we want it */
- d_frame_len = 1 + d_shifting_byte + sizeof(uint16_t);
+
+ /* Length field has been whitened if the option is enabled */
+ if(d_whitening){
+ /* Frame length field is needed for the CRC calculation */
+ d_descrambler.descramble(d_pdu, &d_shifting_byte, 1);
+ /* CRC is not included in the frame length field, but we want it */
+ d_frame_len = 1 + d_pdu[0] + sizeof(uint16_t);
+ }
+ else{
+ /* Frame length field is needed for the CRC calculation */
+ d_pdu[0] = d_shifting_byte;
+ /* CRC is not included in the frame length field, but we want it */
+ d_frame_len = 1 + d_shifting_byte + sizeof(uint16_t);
+ }
have_payload();
}
break;
@@ -258,6 +270,9 @@ namespace gr
d_decoded_bytes++;
if (d_decoded_bytes == d_frame_len) {
+ if(d_whitening){
+ d_descrambler.descramble(d_pdu+1, d_pdu+1, d_frame_len - 1);
+ }
if(!d_check_crc){
message_port_pub (
pmt::mp ("pdu"),
diff --git a/lib/upsat_fsk_frame_acquisition_impl.h b/lib/upsat_fsk_frame_acquisition_impl.h
index ad8a1cb..750224e 100644
--- a/lib/upsat_fsk_frame_acquisition_impl.h
+++ b/lib/upsat_fsk_frame_acquisition_impl.h
@@ -23,6 +23,7 @@
#include
#include
+#include
namespace gr
{
@@ -59,6 +60,7 @@ namespace gr
size_t d_decoded_bytes;
size_t d_decoded_bits;
size_t d_frame_len;
+ whitening d_descrambler;
uint8_t *d_pdu;
inline void
diff --git a/lib/upsat_fsk_frame_encoder_impl.cc b/lib/upsat_fsk_frame_encoder_impl.cc
index 8fae92a..7b2e0f6 100644
--- a/lib/upsat_fsk_frame_encoder_impl.cc
+++ b/lib/upsat_fsk_frame_encoder_impl.cc
@@ -66,7 +66,8 @@ namespace gr
d_max_pdu_len(d_preamble_len + d_sync_word_len + sizeof(uint8_t)
+ UPSAT_MAX_FRAME_LEN + sizeof(uint16_t)),
d_encoded(0),
- d_pdu_len(0)
+ d_pdu_len(0),
+ d_scrambler(0x21, 0x1FF, 9)
{
/* Simplify the logic of the output samples handling */
set_output_multiple(8);
@@ -181,6 +182,16 @@ namespace gr
d_pdu_len += sizeof(uint16_t);
}
+ /*
+ * Whitening is performed on all byes except preamble and SYNC fields
+ */
+ if(d_whitening){
+ d_scrambler.reset();
+ d_scrambler.scramble (d_pdu + d_preamble_len + d_sync_word_len,
+ d_pdu + d_preamble_len + d_sync_word_len,
+ d_pdu_len + 1);
+ }
+
d_pdu_len += d_preamble_len + d_sync_word_len + 1;
}
diff --git a/lib/upsat_fsk_frame_encoder_impl.h b/lib/upsat_fsk_frame_encoder_impl.h
index cffd0c6..0952e0d 100644
--- a/lib/upsat_fsk_frame_encoder_impl.h
+++ b/lib/upsat_fsk_frame_encoder_impl.h
@@ -22,6 +22,7 @@
#define INCLUDED_SATNOGS_UPSAT_FSK_FRAME_ENCODER_IMPL_H
#include
+#include
namespace gr
{
@@ -42,6 +43,7 @@ namespace gr
const size_t d_max_pdu_len;
size_t d_encoded;
size_t d_pdu_len;
+ whitening d_scrambler;
uint8_t *d_pdu;
inline void
diff --git a/lib/whitening.cc b/lib/whitening.cc
new file mode 100644
index 0000000..3c54afa
--- /dev/null
+++ b/lib/whitening.cc
@@ -0,0 +1,109 @@
+/* -*- c++ -*- */
+/*
+ * gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
+ *
+ * Copyright (C) 2016, Libre Space Foundation
+ *
+ * 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, either 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 for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see .
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include
+#include
+#include
+
+namespace gr {
+ namespace satnogs {
+
+ /**
+ * Data whitening and de-whitening class
+ * @param mask the polynomial mask
+ * @param seed the initial seed
+ * @param order the order of the shift register. This is equal to the
+ * number of memory stages.
+ */
+ whitening::whitening (uint32_t mask, uint32_t seed, uint32_t order) :
+ d_lut_len (std::pow (2, order)),
+ d_lut_idx (0)
+ {
+ size_t i;
+ size_t j;
+ uint32_t cnt;
+ uint32_t shift_reg = seed;
+
+ if (order > 32) {
+ throw std::invalid_argument ("The maximum allowed order is 32");
+ }
+
+ d_lut = new uint8_t[d_lut_len];
+
+ for (i = 0; i < d_lut_len; i++) {
+ d_lut[i] = shift_reg & 0xFF;
+ for (j = 0; j < 8; j++) {
+ cnt = bit_count (shift_reg & mask) % 2;
+ shift_reg = shift_reg >> 1;
+ shift_reg |= cnt << (order - 1);
+ }
+ }
+ }
+
+ whitening::~whitening()
+ {
+ delete [] d_lut;
+ }
+
+ /**
+ * Resets the scrambler (or the descrambler) to the initial stage and
+ * the initial seed.
+ */
+ void
+ whitening::reset ()
+ {
+ d_lut_idx = 0;
+ }
+
+ /**
+ * Performs data scrambling
+ * @param out the output buffer
+ * @param in the input buffer
+ * @param len the number of the bytes to be scrambled
+ */
+ void
+ whitening::scramble (uint8_t* out, const uint8_t* in, size_t len)
+ {
+ size_t i;
+ for(i = 0; i < len; i++){
+ out[i] = in[i] ^ d_lut[ (d_lut_idx + i ) % d_lut_len];
+ }
+ d_lut_idx = (d_lut_idx + len ) % d_lut_len;
+ }
+
+ /**
+ * Performs data de-scrambling
+ * @param out the output buffer
+ * @param in the input buffer
+ * @param len the number of the bytes to be de-scrambled
+ */
+ void
+ whitening::descramble (uint8_t* out, const uint8_t* in, size_t len)
+ {
+ scramble(out, in, len);
+ }
+
+ } /* namespace satnogs */
+} /* namespace gr */
+
diff --git a/swig/satnogs_swig.i b/swig/satnogs_swig.i
index ebec1e7..9e1f567 100644
--- a/swig/satnogs_swig.i
+++ b/swig/satnogs_swig.i
@@ -27,6 +27,7 @@
#include "satnogs/frame_encoder.h"
#include "satnogs/upsat_fsk_frame_acquisition.h"
#include "satnogs/upsat_fsk_frame_encoder.h"
+#include "satnogs/whitening.h"
%}
@@ -65,3 +66,4 @@ GR_SWIG_BLOCK_MAGIC2(satnogs, doppler_correction_cc);
GR_SWIG_BLOCK_MAGIC2(satnogs, upsat_fsk_frame_acquisition);
%include "satnogs/upsat_fsk_frame_encoder.h"
GR_SWIG_BLOCK_MAGIC2(satnogs, upsat_fsk_frame_encoder);
+%include "satnogs/whitening.h"