From 3bcd51536348265cf44ed326ccb568a06f96f761 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=2E=20David=20Ib=C3=A1=C3=B1ez?= <jdavid.ibp@gmail.com>
Date: Tue, 3 Aug 2021 12:19:19 +0200
Subject: [PATCH 2/3] Integration with RIOT, to support other boards
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For unknown boards (not directly supported by the library):

- Use micros() for timing, when sending a command

This has been tested with the remote-revb board.

Signed-off-by: J. David Ibáñez <jdavid.ibp@gmail.com>
---
 src/SDI12.h          | 10 +++++++++-
 src/SDI12_boards.cpp | 10 +++++++++-
 src/SDI12_boards.h   | 33 ++++++++++++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/SDI12.h b/src/SDI12.h
index 9ac77f7..6709771 100644
--- a/src/SDI12.h
+++ b/src/SDI12.h
@@ -191,11 +191,19 @@ enum LookaheadMode {
  * processor timer directly.
  */
 #define READTIME sdi12timer.SDI12TimerRead()
-#else
+
+#elif defined(TCNTX)
 /**
  * @brief The function or macro used to read the clock timer value.
  */
 #define READTIME TCNTX
+
+#else
+/**
+ * @brief The function or macro used to read the clock timer value.
+ */
+#define READTIME sdi12timer.SDI12TimerRead()
+
 #endif  // defined(ESP32) || defined(ESP8266)
 
 /**
diff --git a/src/SDI12_boards.cpp b/src/SDI12_boards.cpp
index beb28e8..2159eee 100644
--- a/src/SDI12_boards.cpp
+++ b/src/SDI12_boards.cpp
@@ -275,5 +275,13 @@ sdi12timer_t SDI12Timer::SDI12TimerRead(void) {
 }
 // Unknown board
 #else
-#error "Please define your board timer and pins"
+
+void         SDI12Timer::configSDI12TimerPrescale(void) {}
+void         SDI12Timer::resetSDI12TimerPrescale(void) {}
+sdi12timer_t SDI12Timer::SDI12TimerRead(void) {
+  // Its a one microsecond clock but we want 64uS ticks so divide by 64 i.e. right shift
+  // 6
+  return ((sdi12timer_t)(micros() >> 6));
+}
+
 #endif
diff --git a/src/SDI12_boards.h b/src/SDI12_boards.h
index d91eff4..686444f 100644
--- a/src/SDI12_boards.h
+++ b/src/SDI12_boards.h
@@ -511,7 +511,38 @@ class SDI12Timer {
 
 // Unknown board
 #else
-#error "Please define your board timer and pins"
+
+  /**
+   * @brief Read the processor micros and right shift 6 bits (ie, divide by 64) to get a
+   * 64µs tick.
+   *
+   * @return **sdi12timer_t** The current processor micros
+   */
+  sdi12timer_t SDI12TimerRead(void);
+
+/**
+ * @brief The number of "ticks" of the timer that occur within the timing of one bit
+ * at the SDI-12 baud rate of 1200 bits/second.
+ *
+ * 48MHz / 3 pre-prescaler = 16MHz
+ * 16MHz / 1024 prescaler = 15624 'ticks'/sec = 64 µs / 'tick'
+ * (1 sec/1200 bits) * (1 tick/64 µs) = 13.0208 ticks/bit
+ */
+#define TICKS_PER_BIT 13
+/**
+ * @brief The number of "ticks" of the timer per SDI-12 bit, shifted by 2^10.
+ *
+ * 1/(13.0208 ticks/bit) * 2^10 = 78.6432
+ */
+#define BITS_PER_TICK_Q10 79
+/**
+ * @brief A "fudge factor" to get the Rx to work well.   It mostly works to ensure that
+ * uneven tick increments get rounded up.
+ *
+ * @see https://github.com/SlashDevin/NeoSWSerial/pull/13
+ */
+#define RX_WINDOW_FUDGE 2
+
 #endif
 };
 
-- 
2.34.1