Move packet timestamping into baseband.

Now reads the RTC peripheral at the end of each received packet.
TODO: Improve resolution to milliseconds or better.
TODO: Work back from end of packet to compute timestamp for beginning of packet.
TODO: Reuse ChibiOS RTC code, which isn't used now because ChibiOS on M0 core is responsible for RTC configuration, and including ChibiOS RTC API on M4 will also try to initialize/manage the peripheral.

firmware/common/ais_packet.cpp

@@ -128,8 +128,8 @@ bool Packet::is_valid() const {
 	return length_valid() && crc_ok();
 }
 
-rtc::RTC Packet::received_at() const {
-	return received_at_;
+Timestamp Packet::received_at() const {
+	return packet_.timestamp();
 }
 
 uint32_t Packet::message_id() const {

firmware/common/ais_packet.hpp

@@ -25,9 +25,6 @@
 #include "baseband_packet.hpp"
 #include "field_reader.hpp"
 
-#include "lpc43xx_cpp.hpp"
-using namespace lpc43xx;
-
 #include <cstdint>
 #include <cstddef>
 #include <string>
@@ -51,10 +48,8 @@ using MMSI = uint32_t;
 class Packet {
 public:
 	constexpr Packet(
-		const rtc::RTC& received_at,
 		const baseband::Packet& packet
 	) : packet_ { packet },
-		received_at_ { received_at },
 		field_ { packet_ }
 	{
 	}
@@ -63,7 +58,7 @@ public:
 	
 	bool is_valid() const;
 
-	rtc::RTC received_at() const;
+	Timestamp received_at() const;
 
 	uint32_t message_id() const;
 	MMSI user_id() const;
@@ -85,7 +80,6 @@ private:
 	using CRCReader = FieldReader<baseband::Packet, BitRemapNone>;
 	
 	const baseband::Packet packet_;
-	const rtc::RTC received_at_;
 	const Reader field_;
 
 	const size_t fcs_length = 16;

firmware/common/baseband_packet.hpp

@@ -22,6 +22,8 @@
 #ifndef __BASEBAND_PACKET_H__
 #define __BASEBAND_PACKET_H__
 
+#include "baseband.hpp"
+
 #include <cstddef>
 #include <bitset>
 
@@ -29,6 +31,14 @@ namespace baseband {
 
 class Packet {
 public:
+	void set_timestamp(const Timestamp& value) {
+		timestamp_ = value;
+	}
+	
+	Timestamp timestamp() const {
+		return timestamp_;
+	}
+
 	void add(const bool symbol) {
 		if( count < capacity() ) {
 			data[count++] = symbol;
@@ -53,6 +63,7 @@ public:
 
 private:
 	std::bitset<1408> data;
+	Timestamp timestamp_ { };
 	size_t count { 0 };
 };
 

firmware/common/buffer.hpp

@@ -25,16 +25,50 @@
 #include <cstdint>
 #include <cstddef>
 
+/* LPC43xx RTC structure. Avoiding using the ChibiOS-defined structure because
+ * it pulls in all sorts of dependencies and initialization and other stuff that
+ * the M0 needs to remain in control of.
+ *
+ * But yes, this is a hack, and something better is needed. It's too tangled of
+ * a knot to tackle at the moment, though...
+ */
+#if defined(LPC43XX_M4)
+#include "lpc43xx_m4.h"
+
+struct Timestamp {
+	uint32_t tv_date { 0 };
+	uint32_t tv_time { 0 };
+
+	static Timestamp now() {
+		// Code stolen from LPC43xx rtc_lld.c
+		Timestamp timestamp;
+	    do {
+			timestamp.tv_time = LPC_RTC->CTIME0;
+			timestamp.tv_date = LPC_RTC->CTIME1;
+	    } while( (timestamp.tv_time != LPC_RTC->CTIME0) || (timestamp.tv_date != LPC_RTC->CTIME1) );
+	    return timestamp;
+	}
+};
+#endif
+
+#if defined(LPC43XX_M0)
+#include "lpc43xx_cpp.hpp"
+
+using Timestamp = lpc43xx::rtc::RTC;
+#endif
+
 template<typename T>
 struct buffer_t {
 	T* const p;
 	const size_t count;
 	const uint32_t sampling_rate;
+	const Timestamp timestamp;
 
 	constexpr buffer_t(
 	) : p { nullptr },
 		count { 0 },
-		sampling_rate { 0 }
+		sampling_rate { 0 },
+		timestamp { }
 	{
 	}
 
@@ -42,17 +76,20 @@ struct buffer_t {
 		const buffer_t<T>& other
 	) : p { other.p },
 		count { other.count },
-		sampling_rate { other.sampling_rate }
+		sampling_rate { other.sampling_rate },
+		timestamp { other.timestamp }
 	{
 	}
 
 	constexpr buffer_t(
 		T* const p,
 		const size_t count,
-		const uint32_t sampling_rate = 0
+		const uint32_t sampling_rate = 0,
+		const Timestamp timestamp = { }
 	) : p { p },
 		count { count },
-		sampling_rate { sampling_rate }
+		sampling_rate { sampling_rate },
+		timestamp { timestamp }
 	{
 	}
 };

firmware/common/ert_packet.cpp

@@ -33,8 +33,8 @@ bool Packet::is_valid() const {
 	return true;
 }
 
-rtc::RTC Packet::received_at() const {
-	return received_at_;
+Timestamp Packet::received_at() const {
+	return packet_.timestamp();
 }
 
 Packet::Type Packet::type() const {

firmware/common/ert_packet.hpp

@@ -29,9 +29,6 @@
 #include "baseband_packet.hpp"
 #include "manchester.hpp"
 
-#include "lpc43xx_cpp.hpp"
-using namespace lpc43xx;
-
 namespace ert {
 
 using ID = uint32_t;
@@ -46,11 +43,9 @@ public:
 	};
 
 	Packet(
-		const rtc::RTC& received_at,
 		const Type type,
 		const baseband::Packet& packet
 	) : packet_ { packet },
-		received_at_ { received_at },
 		decoder_ { packet_ },
 		reader_ { decoder_ },
 		type_ { type }
@@ -61,7 +56,7 @@ public:
 	
 	bool is_valid() const;
 
-	rtc::RTC received_at() const;
+	Timestamp received_at() const;
 
 	Type type() const;
 	ID id() const;
@@ -75,7 +70,6 @@ private:
 	using Reader = FieldReader<ManchesterDecoder, BitRemapNone>;
 
 	const baseband::Packet packet_;
-	const rtc::RTC received_at_;
 	const ManchesterDecoder decoder_;
 	const Reader reader_;
 	const Type type_;