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Added a bunch of notes about Radiosonde RX (help !)

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This commit is contained in:
furrtek 2017-10-06 05:35:25 +01:00
parent d3222c27ca
commit f00125879d
4 changed files with 93 additions and 23 deletions
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26
firmware/application/ui_sonde.cpp
View File

@ -53,14 +53,14 @@ SondeView::SondeView(NavigationView& nav) {
field_frequency.set_value(receiver_model.tuning_frequency());
field_frequency.set_step(receiver_model.frequency_step());
field_frequency.on_change = [this](rf::Frequency f) {
receiver_model.set_tuning_frequency(f);
set_target_frequency(f);
field_frequency.set_value(f);
};
field_frequency.on_edit = [this, &nav]() {
// TODO: Provide separate modal method/scheme?
auto new_view = nav.push<FrequencyKeypadView>(receiver_model.tuning_frequency());
new_view->on_changed = [this](rf::Frequency f) {
receiver_model.set_tuning_frequency(f);
set_target_frequency(f);
field_frequency.set_value(f);
};
};
@ -74,6 +74,8 @@ SondeView::SondeView(NavigationView& nav) {
static_cast<int8_t>(receiver_model.lna()),
static_cast<int8_t>(receiver_model.vga()),
});
set_target_frequency(402000000);
/*logger = std::make_unique<SondeLogger>();
if( logger ) {
@ -90,8 +92,15 @@ void SondeView::focus() {
field_vga.focus();
}
void SondeView::on_packet(const sonde::Packet& packet) {
text_debug.set("Got frame !");
void SondeView::on_packet(const baseband::Packet& packet) {
std::string bin_string;
for (size_t i = 0; i < 30; i++) {
bin_string += to_string_dec_uint(packet[i]);
}
text_debug.set(bin_string);
/*if( logger ) {
logger->on_packet(packet);
}*/
@ -100,4 +109,13 @@ void SondeView::on_packet(const sonde::Packet& packet) {
}*/
}
void SondeView::set_target_frequency(const uint32_t new_value) {
target_frequency_ = new_value;
radio::set_tuning_frequency(tuning_frequency());
}
uint32_t SondeView::tuning_frequency() const {
return target_frequency_ - (sampling_rate / 4);
}
} /* namespace ui */

11
firmware/application/ui_sonde.hpp
View File

@ -67,6 +67,7 @@ public:
private:
//std::unique_ptr<SondeLogger> logger { };
uint32_t target_frequency_ { };
FrequencyField field_frequency {
{ 0 * 8, 0 * 8 },
@ -96,12 +97,16 @@ private:
Message::ID::SondePacket,
[this](Message* const p) {
const auto message = static_cast<const SondePacketMessage*>(p);
const sonde::Packet packet { message->type, message->packet };
this->on_packet(packet);
//const sonde::Packet packet { message->type, message->packet };
//this->on_packet(packet);
this->on_packet(message->packet);
}
};
void on_packet(const sonde::Packet& packet);
//void on_packet(const sonde::Packet& packet);
void on_packet(const baseband::Packet& packet);
void set_target_frequency(const uint32_t new_value);
uint32_t tuning_frequency() const;
};
} /* namespace ui */

13
firmware/baseband/proc_sonde.cpp
View File

@ -28,22 +28,23 @@
#include "event_m4.hpp"
SondeProcessor::SondeProcessor() {
decim_0.configure(taps_200k_decim_0.taps, 33554432);
decim_1.configure(taps_200k_decim_1.taps, 131072);
decim_0.configure(taps_11k0_decim_0.taps, 33554432);
decim_1.configure(taps_11k0_decim_1.taps, 131072);
}
void SondeProcessor::execute(const buffer_c8_t& buffer) {
/* 2.4576MHz, 2048 samples */
const auto decim_0_out = decim_0.execute(buffer, dst_buffer);
const auto decimator_out = decim_1.execute(decim_0_out, dst_buffer);
const auto decim_1_out = decim_1.execute(decim_0_out, dst_buffer);
const auto decimator_out = decim_1_out;
/* 307.2kHz, 256 samples */
/* 38.4kHz, 32 samples */
feed_channel_stats(decimator_out);
for(size_t i=0; i<decimator_out.count; i++) {
if( mf_38k4_1t_19k2.execute_once(decimator_out.p[i]) ) {
clock_recovery_fsk_19k2(mf_38k4_1t_19k2.get_output());
if( mf.execute_once(decimator_out.p[i]) ) {
clock_recovery_fsk_4800(mf.get_output());
}
}
}

66
firmware/baseband/proc_sonde.hpp
View File

@ -20,13 +20,61 @@
* Boston, MA 02110-1301, USA.
*/
/* Notes to self (or others, welcome !):
* Sharebrained wrote in matched_filter.hpp that taps should be those of a complex low-pass filter combined with a complex sinusoid, so
* that the filter shifts the spectrum where we want (signal of interest around 0Hz).
*
* In this baseband processor, after decim_0 and decim_1, the signal ends up being sampled at 38400Hz (2457600 / 8 / 8)
* Since the applied shift in ui_sonde.cpp is -fs/4 = -2457600/4 = -614400Hz to avoid the DC spike, the FSK signal ends up being
* shifted by 614400 / 8 / 8 = 9600Hz. So decim_1_out should look like this:
*
* _______________|__/'\__________
* -C A B C
*
* A is the DC spike at 0Hz
* B is the FSK signal shifted right at 9600Hz
* C is the bandwidth edge at 19200Hz
*
* Taps should be computed to shift the whole spectrum by -9600Hz ("left") so that it looks like this:
*
* ______________/'\______________
* -C D C
*
* A should have been filtered off ?
* D is B around 0Hz now
*
* Then the clock_recovery function should be happy :)
*
* Mathworks.com says:
* In the case of a single-rate FIR design, we simply multiply each set of coefficients by (aka 'heterodyne with') a complex exponential.
*
* Can SciPy's remez function be used for this ? See tools/firtest.py
* GnuRadio's firdes only outputs an odd number of taps
*
* ---------------------------------------------------------------------
*
* Looking at the AIS baseband processor:
*
* Copied everything necessary to get decim_1_out (so same 8 * 8 = 64 decimation factor)
* The samplerate is also the same (2457600)
* After the matching filter, the data is decimated by 2 so the final samplerate for clock_recovery is 38400 / 2 = 19200Hz.
* Like here, the shift used is fs/4, so decim_1_out should be looking similar.
* The AIS signal deviates by 2400 (4800Hz signal width), the symbol rate is 9600.
*
* The matched filter's input samplerate is 38400Hz, to get a 9600Hz shift it must use 4 taps ?
* To obtain unity gain, the sinusoid length must be / by the number of taps ?
*
* See ais_baseband.hpp
*
* */
#ifndef __PROC_SONDE_H__
#define __PROC_SONDE_H__
#include "baseband_processor.hpp"
#include "baseband_thread.hpp"
#include "rssi_thread.hpp"
#include "proc_tpms.hpp"
#include "proc_ais.hpp"
#include "channel_decimator.hpp"
#include "matched_filter.hpp"
@ -36,8 +84,6 @@
#include "packet_builder.hpp"
#include "baseband_packet.hpp"
#include "ook.hpp"
#include "message.hpp"
#include "portapack_shared_memory.hpp"
@ -63,13 +109,13 @@ private:
dst.size()
};
dsp::decimate::FIRC8xR16x24FS4Decim4 decim_0 { };
dsp::decimate::FIRC16xR16x16Decim2 decim_1 { };
dsp::decimate::FIRC8xR16x24FS4Decim8 decim_0 { };
dsp::decimate::FIRC16xR16x32Decim8 decim_1 { };
dsp::matched_filter::MatchedFilter mf { baseband::ais::square_taps_38k4_1t_p, 2 };
dsp::matched_filter::MatchedFilter mf_38k4_1t_19k2 { rect_taps_307k2_38k4_1t_19k2_p, 8 };
clock_recovery::ClockRecovery<clock_recovery::FixedErrorFilter> clock_recovery_fsk_19k2 {
38400, 19200, { 0.0555f },
// AIS: 19200, 9600
clock_recovery::ClockRecovery<clock_recovery::FixedErrorFilter> clock_recovery_fsk_4800 {
19200, 4800, { 0.0555f },
[this](const float raw_symbol) {
const uint_fast8_t sliced_symbol = (raw_symbol >= 0.0f) ? 1 : 0;
this->packet_builder_fsk_4800_M10.execute(sliced_symbol);
@ -78,7 +124,7 @@ private:
PacketBuilder<BitPattern, NeverMatch, FixedLength> packet_builder_fsk_4800_M10 {
{ 0b11001100110011001010011001001100, 32, 1 },
{ },
{ 102 * 8 },
{ 50 }, // { 102 * 8 },
[this](const baseband::Packet& packet) {
const SondePacketMessage message { sonde::Packet::Type::M10, packet };
shared_memory.application_queue.push(message);