Suga koubou
SMPTE timedode (LTC) decode library for mbed
SMPTE timedode (LTC) decode library
SMPTEタイムコードをデコード（受信）・エンコード（送信）するライブラリです。
平衡／不平衡／サウンド等によるLTC信号は、適当な回路で整形して入力してください。
出力は適当なドライバ回路を設けてください。
簡易的なプログラムのため、細かいフラグなどは無視しています。
LPC1768 専用、Timer 2 を占有します。
Sample
Import programLTC_SMPTE_sample
SMPTE timedode (LTC) decode library for mbed https://developer.mbed.org/users/okini3939/code/LTC_SMPTE/
Last commit 13 Apr 2018 by 
Suga koubou
Diff: LTC_SMPTE.cpp
- Revision:
- 0:8d19e2158eb4
- Child:
- 1:63ceee4bfd05
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/LTC_SMPTE.cpp Mon Nov 16 12:51:43 2015 +0000
@@ -0,0 +1,129 @@
+/**
+ * SMPTE timedode (LTC) decode library for mbed
+ * Copyright (c) 2015 Suga
+ * Released under the MIT License: http://mbed.org/license/mit
+ */
+/** @file
+ * @brief SMPTE timedode (LTC) decode library for mbed
+ */
+
+#include "LTC_SMPTE.h"
+
+// pulse width: 416.7us(30fps)
+// 80bit x 30frame/s --> 416.7us/bit
+#define ONE_TIME_MIN 100
+#define ONE_TIME_MAX 250
+#define ZERO_TIME_MIN 300
+#define ZERO_TIME_MAX 500
+
+LTC_SMPTE::LTC_SMPTE (PinName input) : _input(input) {
+
+ mode = 0;
+ count = 0;
+ oneflg = 0;
+ direction = 0;
+ received = 0;
+
+ _input.mode(PullUp);
+ _input.fall(this, <C_SMPTE::isr_change);
+ _input.rise(this, <C_SMPTE::isr_change);
+ _timer.start();
+}
+
+void LTC_SMPTE::isr_change () {
+ int b, t;
+
+ t = _timer.read_us();
+ _timer.reset();
+
+ if (t >= ONE_TIME_MIN && t < ONE_TIME_MAX) {
+ if (oneflg == 0) {
+ oneflg = 1;
+ return;
+ } else {
+ oneflg = 0;
+ b = 1;
+ }
+ } else
+ if (t >= ZERO_TIME_MIN && t < ZERO_TIME_MAX) {
+ oneflg = 0;
+ b = 0;
+ } else {
+ return;
+ }
+
+ if (mode == 0) {
+ // sync word
+ if (b) {
+ // 1
+ if (count == 12) {
+ // error
+ count = 0;
+ } else
+ if (count == 13) {
+ // fwd
+ direction = 1;
+ count = 0;
+ mode = 1;
+ bit = 1;
+ } else {
+ count ++;
+ }
+ } else {
+ // 0
+ if (count == 12) {
+ count ++;
+ } else
+ if (count == 13) {
+ // rev
+ direction = -1;
+ count = 0;
+ mode = 1;
+ bit = 1;
+ } else {
+ // error
+ count = 0;
+ }
+ }
+
+ } else {
+ // time code
+ if (b) {
+ code[count] |= bit; // 1
+ } else {
+ code[count] &= ~bit; // 0
+ }
+ bit <<= 1;
+ if (bit >= 0x100) {
+ bit = 1;
+ count ++;
+ if (count >= 8) {
+ count = 0;
+ mode = 0;
+ parse_code();
+ }
+ }
+ }
+}
+
+void LTC_SMPTE::parse_code () {
+ frame = (code[1] & 0x03) * 10 + (code[0] & 0x0f);
+ sec = (code[3] & 0x07) * 10 + (code[2] & 0x0f);
+ min = (code[5] & 0x07) * 10 + (code[4] & 0x0f);
+ hour = (code[7] & 0x03) * 10 + (code[6] & 0x0f);
+ drop = code[1] & (1<<2) ? 1 : 0;
+ received = 1;
+}
+
+void LTC_SMPTE::read (int *hour, int *min, int *sec, int *frame, int *dir) {
+ *hour = this->hour;
+ *min = this->min;
+ *sec = this->sec;
+ *frame = this->frame;
+ if (dir) *dir = this->direction;
+ received = 0;
+}
+
+int LTC_SMPTE::isReceived () {
+ return received;
+}