diff --git a/grc/satellites/upsat/satnogs_upsat_fsk_frame_acquisition.xml b/grc/satellites/upsat/satnogs_upsat_fsk_frame_acquisition.xml
index 9db4794..698f2e8 100644
--- a/grc/satellites/upsat/satnogs_upsat_fsk_frame_acquisition.xml
+++ b/grc/satellites/upsat/satnogs_upsat_fsk_frame_acquisition.xml
@@ -3,7 +3,7 @@
UPSAT FSK Frame Acquisition
satnogs_upsat_fsk_frame_acquisition
import satnogs
- satnogs.upsat_fsk_frame_acquisition($preamble, $sync_word, $whitening, $manchester, $check_crc, $ax_25, $whitening_mask, $whitening_seed, $whitening_order)
+ satnogs.upsat_fsk_frame_acquisition($preamble, $sync_word, $whitening, $manchester, $check_crc, $ax_25, $whitening_mask, $whitening_seed, $whitening_order, $packet_len)
Frame Preamble
@@ -87,12 +87,19 @@
int
-
+
Whitening order
whitening_order
17
int
+
+
+ Packet length
+ packet_len
+ 0
+ int
+
in
diff --git a/include/satnogs/upsat_fsk_frame_acquisition.h b/include/satnogs/upsat_fsk_frame_acquisition.h
index a5cf465..3d28b9b 100644
--- a/include/satnogs/upsat_fsk_frame_acquisition.h
+++ b/include/satnogs/upsat_fsk_frame_acquisition.h
@@ -68,6 +68,10 @@ namespace gr
* @param whitening_mask the polynomial of the scrambler
* @param whitening_seed the initial seed of the scrambler
* @param whitening_order the size of the scrambler's LFSR
+ * @param packet_len if set to 0 the decoder enters the variable
+ * packet length mode, where the packet length is indicated from the
+ * first byte after the SYNC word. Otherwise this field specifies the
+ * payload length in bytes.
*/
static sptr
make (const std::vector &preamble,
@@ -76,7 +80,8 @@ namespace gr
bool ax25_format = false,
uint32_t whitening_mask = 0x1001,
uint32_t whitening_seed = 0x1FF,
- uint32_t whitening_order = 17);
+ uint32_t whitening_order = 17,
+ size_t packet_len = 0);
};
} // namespace satnogs
diff --git a/lib/upsat_fsk_frame_acquisition_impl.cc b/lib/upsat_fsk_frame_acquisition_impl.cc
index 53a1c2c..92213a2 100644
--- a/lib/upsat_fsk_frame_acquisition_impl.cc
+++ b/lib/upsat_fsk_frame_acquisition_impl.cc
@@ -42,14 +42,16 @@ namespace gr
bool check_crc, bool ax25_format,
uint32_t whitening_mask,
uint32_t whitening_seed,
- uint32_t whitening_order)
+ uint32_t whitening_order,
+ size_t packet_len)
{
return gnuradio::get_initial_sptr (
new upsat_fsk_frame_acquisition_impl (preamble, sync_word, whitening,
manchester, check_crc,
ax25_format, whitening_mask,
whitening_seed,
- whitening_order));
+ whitening_order,
+ packet_len));
}
/*
@@ -59,7 +61,8 @@ namespace gr
const std::vector &preamble,
const std::vector &sync_word, bool whitening, bool manchester,
bool check_crc, bool ax25_format, uint32_t whitening_mask,
- uint32_t whitening_seed, uint32_t whitening_order) :
+ uint32_t whitening_seed, uint32_t whitening_order,
+ size_t packet_len) :
gr::sync_block ("upsat_fsk_frame_acquisition",
gr::io_signature::make (1, 1, sizeof(float)),
gr::io_signature::make (0, 0, 0)),
@@ -78,6 +81,7 @@ namespace gr
d_manchester (manchester),
d_check_crc (check_crc),
d_is_ax25 (ax25_format),
+ d_var_packet_len(packet_len == 0),
d_state (SEARCHING),
d_shifting_byte (0x0),
d_decoded_bytes (0),
@@ -106,6 +110,9 @@ namespace gr
d_pdu = new uint8_t[UPSAT_MAX_FRAME_LEN];
d_ax25_tmp_buf = new uint8_t[2 * UPSAT_MAX_FRAME_LEN * 8];
d_ax25_buf = new uint8_t[2 * UPSAT_MAX_FRAME_LEN];
+
+ /* If the fixed packet length is set, store the expected frame size */
+ d_frame_len = packet_len;
}
/*
@@ -180,7 +187,12 @@ namespace gr
{
LOG_DEBUG("Enter have payload");
d_state = HAVE_PAYLOAD;
- d_decoded_bytes = 1;
+ if(d_var_packet_len) {
+ d_decoded_bytes = 1;
+ }
+ else {
+ d_decoded_bytes = 0;
+ }
d_decoded_bits = 0;
}
@@ -219,7 +231,11 @@ namespace gr
uint16_t crc_calc;
size_t ax25_frame_len = 0;
ax25_decode_status_t status;
+ size_t payload_len;
+ uint8_t *payload;
+
const float *in = (const float *) input_items[0];
+
for (i = 0; i < noutput_items; i++) {
slice_and_shift (in[i]);
@@ -276,7 +292,12 @@ namespace gr
if (d_shifting_byte == d_sync_word[d_decoded_bytes]) {
d_decoded_bytes++;
if (d_decoded_bytes == d_sync_word_len) {
- have_frame_len ();
+ if(d_var_packet_len) {
+ have_frame_len ();
+ }
+ else{
+ have_payload();
+ }
}
}
else {
@@ -307,6 +328,15 @@ namespace gr
case HAVE_PAYLOAD:
d_decoded_bits++;
if (d_decoded_bits == 8) {
+ if(d_var_packet_len) {
+ payload = d_pdu + 1;
+ payload_len = d_frame_len - 1;
+ }
+ else{
+ payload = d_pdu;
+ payload_len = d_frame_len;
+ }
+
d_decoded_bits = 0;
d_pdu[d_decoded_bytes] = d_shifting_byte;
d_decoded_bytes++;
@@ -314,9 +344,9 @@ namespace gr
if (d_decoded_bytes == d_frame_len) {
if (d_is_ax25) {
- unpack_ax25_bytes (d_frame_len - 1);
+ unpack_ax25_bytes (payload_len);
status = ax25_decode (d_ax25_buf, &ax25_frame_len,
- d_ax25_tmp_buf, (d_frame_len - 1) * 8);
+ d_ax25_tmp_buf, payload_len * 8);
if (status == AX25_DEC_OK) {
/* Skip the AX.25 header */
message_port_pub (
@@ -335,15 +365,14 @@ namespace gr
}
if (d_whitening) {
- d_descrambler.descramble (d_pdu + 1, d_pdu + 1,
- d_frame_len - 1);
+ d_descrambler.descramble (payload, payload, payload_len);
}
if (!d_check_crc) {
message_port_pub (
pmt::mp ("pdu"),
- pmt::make_blob (d_pdu + 1,
- d_frame_len - 1 - sizeof(uint16_t)));
+ pmt::make_blob (payload,
+ payload_len - sizeof(uint16_t)));
reset_state ();
break;
}
@@ -357,8 +386,8 @@ namespace gr
if (crc_calc == crc_received) {
message_port_pub (
pmt::mp ("pdu"),
- pmt::make_blob (d_pdu + 1,
- d_frame_len - 1 - sizeof(uint16_t)));
+ pmt::make_blob (payload,
+ payload_len - sizeof(uint16_t)));
}
else {
LOG_WARN("Frame with wrong CRC got 0x%x calc 0x%x",
diff --git a/lib/upsat_fsk_frame_acquisition_impl.h b/lib/upsat_fsk_frame_acquisition_impl.h
index ed5b970..74e760e 100644
--- a/lib/upsat_fsk_frame_acquisition_impl.h
+++ b/lib/upsat_fsk_frame_acquisition_impl.h
@@ -57,6 +57,7 @@ namespace gr
const bool d_manchester;
const bool d_check_crc;
const bool d_is_ax25;
+ const bool d_var_packet_len;
decoding_state_t d_state;
uint8_t d_shifting_byte;
size_t d_decoded_bytes;
@@ -92,7 +93,8 @@ namespace gr
bool check_crc, bool ax25_format,
uint32_t whitening_mask,
uint32_t whitening_seed,
- uint32_t whitening_order);
+ uint32_t whitening_order,
+ size_t packet_len);
~upsat_fsk_frame_acquisition_impl ();
// Where all the action really happens