From eebed918e904dad99d1d912b86e928564d0f0a46 Mon Sep 17 00:00:00 2001
From: Richard Meadows <richardeoin@gmail.com>
Date: Sun, 15 Mar 2015 21:35:42 +0000
Subject: [PATCH] Measure error of xosc in hz relative to gps timepulse

---
 firmware/src/main.c |  4 +++-
 firmware/src/xosc.c | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/firmware/src/main.c b/firmware/src/main.c
index 22d2e11..d0ab5d4 100644
--- a/firmware/src/main.c
+++ b/firmware/src/main.c
@@ -291,7 +291,9 @@ void init(void)
 
 void xosc_measure_callback(uint32_t result)
 {
-  result++;
+  int32_t error = result - XOSC_FREQUENCY;
+
+  error++;
 }
 
 uint8_t telemetry_trigger_flag = 0;
diff --git a/firmware/src/xosc.c b/firmware/src/xosc.c
index fc7e426..aa7c9f7 100644
--- a/firmware/src/xosc.c
+++ b/firmware/src/xosc.c
@@ -235,6 +235,7 @@ void measure_xosc_disable(enum xosc_measurement_t measurement_t) {
  */
 void TC2_Handler(void) {
   uint32_t capture_value;
+  uint32_t source_freq;
 
   if (tc_get_status(TC2) & TC_STATUS_CHANNEL_0_MATCH) {
     tc_clear_status(TC2, TC_STATUS_CHANNEL_0_MATCH);
@@ -247,9 +248,19 @@ void TC2_Handler(void) {
       /* Measurement done. Read off data */
       capture_value = tc_get_capture_value(TC2, 0);
 
+      /* Calcuate the frequency of XOSC relative to this source */
+      switch (_measurement_t) {
+      case XOSC_MEASURE_OSC8M:
+        source_freq = capture_value * XOSC_COUNT_RESOLUTION;
+        break;
+      case XOSC_MEASURE_TIMEPULSE:
+        source_freq = capture_value * XOSC_COUNT_RESOLUTION * GPS_TIMEPULSE_FREQ;
+        break;
+      }
+
       /* Callback if we have one */
       if (_callback) {
-        _callback(capture_value * XOSC_COUNT_RESOLUTION);
+        _callback(source_freq);
       }
 
       /* Disable measurement system */