From 38389d8fef88fe74944eb65e920616454fc1b36b Mon Sep 17 00:00:00 2001
From: Andy Spencer <andy753421@gmail.com>
Date: Mon, 3 Mar 2014 17:54:44 +0000
Subject: [PATCH] Start work on interfaces

---
 hw2/main.cpp | 120 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)

diff --git a/hw2/main.cpp b/hw2/main.cpp
index a43bc8e..436f750 100644
--- a/hw2/main.cpp
+++ b/hw2/main.cpp
@@ -1,8 +1,128 @@
 #include "mbed.h"
 
+/**
+ * Mode of operation:
+ *   Devices 1 and 2 synchronize clocks using serial messages.
+ *
+ *   1. Each serial message timestamped using the hardware timer capture
+ *      registers in both the sender and receiver.
+ *   2. The sender transmits the send timestamp during the next time-sync
+ *      message.
+ *   3. The receiver then compares the senders timestamp with it's own
+ *      timestamp for the corresponding messages and calculates an offset.
+ *   4. The offset is used to compensate the receivers local clock.
+ *
+ *   Time synchronization is performed in both directions.
+ */
+
+/***********************
+ * Message Definitions *
+ ***********************/
+
+#define MSG_HEADER 0x1234
+
+typedef enum {
+	MSG_ID_SYNC,       // Time synchronization
+	MSG_ID_EVENT,      // Event occurred
+} msgid_t;
+
+typedef struct {
+	uint32_t seconds;  // Seconds since 1970 (without leap seconds)
+	uint32_t nanosec;  // Nanoseconds since 'seconds'
+} ntime_t;
+
+typedef struct {
+	uint16_t header;   // Message Header
+	uint16_t mesgid;   // Message ID
+	uint16_t length;   // Body length
+	uint16_t cksum;    // Body checksum
+} header_t;
+
+typedef struct {
+	uint16_t seq;      // Current sequence counter
+	uint16_t prev;     // Sequence of previous message
+	ntime_t  time;     // Time of previous message
+} sync_msg_t;
+
+typedef struct {
+	uint16_t device;   // Device ID
+	uint16_t event;    // Event ID
+	ntime_t  time;     // Timestamp
+} event_msg_t;
+
+/*******************
+ * Timer functions *
+ *******************/
+
+/**
+ * Generate time stamp for an async event:
+ *   time:  drift compensated wall-clock time
+ *   stamp: event timestamp from Timer/PWM Module
+ */
+void time_stamp(ntime_t *time, uint32_t stamp)
+{
+	// todo
+}
+
+/**
+ * Compensate the Real-Time-Clock oscillator for
+ * temperature and drift errors. Called at 1Hz and
+ * synchronous to the RTC 1Hz output.
+ */
+void time_rtc_comp(void)
+{
+	// todo
+}
+
+/**
+ * Synchronize the timer internal state with updates
+ * from an external time sync message.
+ *   ours: our internal timestamp for the event
+ *   ref:  reference timestamp from the other device
+ */
+void time_ext_sync(ntime_t *ours, ntime_t *ref)
+{
+	// todo
+}
+
+/************************
+ * Serial I/O functions *
+ ************************/
+
+/**
+ * Output time sync message
+ */
+void serial_send_sync(void)
+{
+}
+
+/**
+ * Output external event received message
+ *   event: id of the received event
+ *   time:  compensated timestamp of the event 
+ */
+void serial_send_event(uint16_t event, ntime_t *time)
+{
+}
+
+/**
+ * Process serial receive messages
+ */
+void serial_receive(void)
+{
+}
+
+/********************
+ * Data definitions *
+ ********************/
+
 DigitalOut led1(LED1);
 DigitalOut led2(LED2);
 
+/********
+ * Main *
+ ********/
+
 int main(int argc, char **argv)
 {
     while (1) {
-- 
2.43.2