Add the POCSAG transmitter.

2026-05-07 13:37:48 +00:00 · 2018-06-06 20:27:46 +01:00 · 2018-06-06 20:27:46 +01:00 · 20a0a875f3
commit 20a0a875f3
parent d6c1bea80a
12 changed files with 335 additions and 44 deletions
--- a/POCSAGTX.cpp
+++ b/POCSAGTX.cpp
@ -0,0 +1,128 @@
+/*
+ *   Copyright (C) 2009-2018 by Jonathan Naylor G4KLX
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "Config.h"
+#include "Globals.h"
+#include "POCSAGTX.h"
+
+const uint16_t POCSAG_PREAMBLE_LENGTH_BYTES = 576U / 8U;
+
+const uint16_t POCSAG_FRAME_LENGTH_BYTES = 17U * sizeof(uint32_t);
+
+const uint16_t POCSAG_RADIO_SYMBOL_LENGTH = 20U;
+
+const q15_t POCSAG_LEVEL0[] = { 3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155,  3155};
+const q15_t POCSAG_LEVEL1[] = {-3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155, -3155};
+
+const uint8_t POCSAG_SYNC = 0xAAU;
+
+CPOCSAGTX::CPOCSAGTX() :
+m_buffer(4000U),
+m_poBuffer(),
+m_poLen(0U),
+m_poPtr(0U),
+m_txDelay(POCSAG_PREAMBLE_LENGTH_BYTES)
+{
+}
+
+void CPOCSAGTX::process()
+{
+  if (m_buffer.getData() == 0U && m_poLen == 0U)
+    return;
+
+  if (m_poLen == 0U) {
+    if (!m_tx) {
+      for (uint16_t i = 0U; i < m_txDelay; i++)
+        m_poBuffer[m_poLen++] = POCSAG_SYNC;
+    } else {
+      for (uint8_t i = 0U; i < POCSAG_FRAME_LENGTH_BYTES; i++) {
+        uint8_t c = m_buffer.get();
+        m_poBuffer[m_poLen++] = c;
+      }
+    }
+
+    m_poPtr = 0U;
+  }
+
+  if (m_poLen > 0U) {
+    uint16_t space = io.getSpace();
+    
+    while (space > (8U * POCSAG_RADIO_SYMBOL_LENGTH)) {
+      uint8_t c = m_poBuffer[m_poPtr++];
+      writeByte(c);
+
+      space -= 8U * POCSAG_RADIO_SYMBOL_LENGTH;
+      
+      if (m_poPtr >= m_poLen) {
+        m_poPtr = 0U;
+        m_poLen = 0U;
+        return;
+      }
+    }
+  }
+}
+
+uint8_t CPOCSAGTX::writeData(const uint8_t* data, uint8_t length)
+{
+  if (length != POCSAG_FRAME_LENGTH_BYTES)
+    return 4U;
+
+  uint16_t space = m_buffer.getSpace();
+  if (space < POCSAG_FRAME_LENGTH_BYTES)
+    return 5U;
+
+  for (uint8_t i = 0U; i < POCSAG_FRAME_LENGTH_BYTES; i++)
+    m_buffer.put(data[i]);
+
+  return 0U;
+}
+
+void CPOCSAGTX::writeByte(uint8_t c)
+{
+  q15_t buffer[POCSAG_RADIO_SYMBOL_LENGTH * 8U];
+
+  const uint8_t MASK = 0x80U;
+
+  uint8_t n = 0U;
+  for (uint8_t i = 0U; i < 8U; i++, c <<= 1, n += POCSAG_RADIO_SYMBOL_LENGTH) {
+    switch (c & MASK) {
+      case 0x80U:
+        ::memcpy(buffer + n, POCSAG_LEVEL1, POCSAG_RADIO_SYMBOL_LENGTH * sizeof(q15_t));
+        break;
+      default:
+        ::memcpy(buffer + n, POCSAG_LEVEL0, POCSAG_RADIO_SYMBOL_LENGTH * sizeof(q15_t));
+        break;
+    }
+  }
+
+  io.write(STATE_POCSAG, buffer, POCSAG_RADIO_SYMBOL_LENGTH * 8U);
+}
+
+void CPOCSAGTX::setTXDelay(uint8_t delay)
+{
+  m_txDelay = POCSAG_PREAMBLE_LENGTH_BYTES + uint16_t(delay);
+
+  if (m_txDelay > 1200U)
+    m_txDelay = 1200U;
+}
+
+uint8_t CPOCSAGTX::getSpace() const
+{
+  return m_buffer.getSpace() / POCSAG_FRAME_LENGTH_BYTES;
+}
+