Add carrier operated relay support to dvmbridge.

configs/bridge-config.example.yml

@@ -181,3 +181,13 @@ system:
     rtsPttPort: "/dev/ttyUSB0"
     # Hold-off time (ms) before clearing RTS PTT after last audio output.
     rtsPttHoldoffMs: 250
+
+    # CTS COR Configuration
+    # Flag indicating whether CTS-based COR detection is enabled.
+    ctsCorEnable: false
+    # Serial port device for CTS COR (e.g., /dev/ttyUSB0). Often same as RTS PTT.
+    ctsCorPort: "/dev/ttyUSB0"
+    # Flag indicating whether to invert COR logic (if true, COR LOW triggers instead of HIGH).
+    ctsCorInvert: false
+    # Hold-off time (ms) before ending call after CTS COR deasserts.
+    ctsCorHoldoffMs: 250

src/bridge/CtsCorController.cpp

@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Digital Voice Modem - Bridge
+ * GPLv2 Open Source. Use is subject to license terms.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ *  Copyright (C) 2025 Lorenzo L. Romero, K2LLR
+ */
+/**
+ * @file CtsCorController.cpp
+ * @ingroup bridge
+ */
+
+#include "Defines.h"
+#include "CtsCorController.h"
+
+#if !defined(_WIN32)
+#include <errno.h>
+#endif
+
+CtsCorController::CtsCorController(const std::string& port)
+    : m_port(port), m_isOpen(false), m_ownsFd(true)
+#if defined(_WIN32)
+    , m_fd(INVALID_HANDLE_VALUE)
+#else
+    , m_fd(-1)
+#endif // defined(_WIN32)
+{
+}
+
+CtsCorController::~CtsCorController()
+{
+    close();
+}
+
+bool CtsCorController::open(int reuseFd)
+{
+    if (m_isOpen)
+        return true;
+
+#if defined(_WIN32)
+    std::string deviceName = m_port;
+    if (deviceName.find("\\\\.\\") == std::string::npos) {
+        deviceName = "\\\\." + m_port;
+    }
+
+    m_fd = ::CreateFileA(deviceName.c_str(), GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
+    if (m_fd == INVALID_HANDLE_VALUE) {
+        ::LogError(LOG_HOST, "Cannot open CTS COR device - %s, err=%04lx", m_port.c_str(), ::GetLastError());
+        return false;
+    }
+
+    DCB dcb;
+    if (::GetCommState(m_fd, &dcb) == 0) {
+        ::LogError(LOG_HOST, "Cannot get the attributes for %s, err=%04lx", m_port.c_str(), ::GetLastError());
+        ::CloseHandle(m_fd);
+        m_fd = INVALID_HANDLE_VALUE;
+        return false;
+    }
+
+    dcb.BaudRate = 9600;
+    dcb.ByteSize = 8;
+    dcb.Parity = NOPARITY;
+    dcb.fParity = FALSE;
+    dcb.StopBits = ONESTOPBIT;
+    dcb.fInX = FALSE;
+    dcb.fOutX = FALSE;
+    dcb.fOutxCtsFlow = FALSE;
+    dcb.fOutxDsrFlow = FALSE;
+    dcb.fDsrSensitivity = FALSE;
+    dcb.fDtrControl = DTR_CONTROL_DISABLE;
+    dcb.fRtsControl = RTS_CONTROL_DISABLE;
+
+    if (::SetCommState(m_fd, &dcb) == 0) {
+        ::LogError(LOG_HOST, "Cannot set the attributes for %s, err=%04lx", m_port.c_str(), ::GetLastError());
+        ::CloseHandle(m_fd);
+        m_fd = INVALID_HANDLE_VALUE;
+        return false;
+    }
+
+#else
+    // If reusing an existing file descriptor from RTS PTT, don't open a new one
+    if (reuseFd >= 0) {
+        m_fd = reuseFd;
+        m_ownsFd = false; // Only COR can close file descriptor
+        ::LogInfo(LOG_HOST, "CTS COR Controller reusing file descriptor from RTS PTT on %s", m_port.c_str());
+        m_isOpen = true;
+        return true;
+    }
+
+    m_ownsFd = true; // COR owns the file descriptor
+
+    // Open port if not available
+    m_fd = ::open(m_port.c_str(), O_RDONLY | O_NOCTTY | O_NDELAY, 0);
+    if (m_fd < 0) {
+        // Try rw if ro fails
+        m_fd = ::open(m_port.c_str(), O_RDWR | O_NOCTTY | O_NDELAY, 0);
+        if (m_fd < 0) {
+            ::LogError(LOG_HOST, "Cannot open CTS COR device - %s", m_port.c_str());
+            return false;
+        }
+    }
+
+    if (::isatty(m_fd) == 0) {
+        ::LogError(LOG_HOST, "%s is not a TTY device", m_port.c_str());
+        ::close(m_fd);
+        m_fd = -1;
+        return false;
+    }
+
+    // Save current RTS state before configuring termios
+    int savedModemState = 0;
+    if (::ioctl(m_fd, TIOCMGET, &savedModemState) < 0) {
+        ::LogError(LOG_HOST, "Cannot get the control attributes for %s", m_port.c_str());
+        ::close(m_fd);
+        m_fd = -1;
+        return false;
+    }
+    bool savedRtsState = (savedModemState & TIOCM_RTS) != 0;
+
+    if (!setTermios()) {
+        ::close(m_fd);
+        m_fd = -1;
+        return false;
+    }
+
+    // Restore RTS to its original state
+    int currentModemState = 0;
+    if (::ioctl(m_fd, TIOCMGET, &currentModemState) < 0) {
+        ::LogError(LOG_HOST, "Cannot get the control attributes for %s after termios", m_port.c_str());
+        ::close(m_fd);
+        m_fd = -1;
+        return false;
+    }
+    bool currentRtsState = (currentModemState & TIOCM_RTS) != 0;
+    if (currentRtsState != savedRtsState) {
+        // Restore RTS to original state
+        if (savedRtsState) {
+            currentModemState |= TIOCM_RTS;
+        } else {
+            currentModemState &= ~TIOCM_RTS;
+        }
+        if (::ioctl(m_fd, TIOCMSET, &currentModemState) < 0) {
+            ::LogError(LOG_HOST, "Cannot restore RTS state for %s", m_port.c_str());
+            ::close(m_fd);
+            m_fd = -1;
+            return false;
+        }
+        ::LogDebug(LOG_HOST, "CTS COR: Restored RTS to %s on %s", savedRtsState ? "HIGH" : "LOW", m_port.c_str());
+    }
+#endif // defined(_WIN32)
+
+    ::LogInfo(LOG_HOST, "CTS COR Controller opened on %s (RTS preserved)", m_port.c_str());
+    m_isOpen = true;
+    return true;
+}
+
+void CtsCorController::close()
+{
+    if (!m_isOpen)
+        return;
+
+#if defined(_WIN32)
+    if (m_fd != INVALID_HANDLE_VALUE) {
+        ::CloseHandle(m_fd);
+        m_fd = INVALID_HANDLE_VALUE;
+    }
+#else
+    // Only close the file descriptor if we opened it ourselves
+    // If we're reusing a descriptor from RTS PTT, don't close it
+    if (m_fd != -1 && m_ownsFd) {
+        ::close(m_fd);
+        m_fd = -1;
+    } else if (m_fd != -1 && !m_ownsFd) {
+        m_fd = -1;
+    }
+#endif // defined(_WIN32)
+
+    m_isOpen = false;
+    ::LogInfo(LOG_HOST, "CTS COR Controller closed");
+}
+
+bool CtsCorController::isCtsAsserted()
+{
+    if (!m_isOpen)
+        return false;
+
+#if defined(_WIN32)
+    DWORD modemStat = 0;
+    if (::GetCommModemStatus(m_fd, &modemStat) == 0) {
+        ::LogError(LOG_HOST, "Cannot read modem status for %s, err=%04lx", m_port.c_str(), ::GetLastError());
+        return false;
+    }
+    return (modemStat & MS_CTS_ON) != 0;
+#else
+    int modemState = 0;
+    if (::ioctl(m_fd, TIOCMGET, &modemState) < 0) {
+        ::LogError(LOG_HOST, "Cannot get the control attributes for %s", m_port.c_str());
+        return false;
+    }
+    return (modemState & TIOCM_CTS) != 0;
+#endif // defined(_WIN32)
+}
+
+bool CtsCorController::setTermios()
+{
+#if !defined(_WIN32)
+    termios termios;
+    if (::tcgetattr(m_fd, &termios) < 0) {
+        ::LogError(LOG_HOST, "Cannot get the attributes for %s", m_port.c_str());
+        return false;
+    }
+
+    termios.c_iflag &= ~(IGNBRK | BRKINT | IGNPAR | PARMRK | INPCK);
+    termios.c_iflag &= ~(ISTRIP | INLCR | IGNCR | ICRNL);
+    termios.c_iflag &= ~(IXON | IXOFF | IXANY);
+    termios.c_oflag &= ~(OPOST);
+    // Important: Disable hardware flow control (CRTSCTS) to avoid affecting RTS
+    // We only want to read CTS, not control RTS
+    termios.c_cflag &= ~(CSIZE | CSTOPB | PARENB | CRTSCTS);
+    termios.c_cflag |= (CS8 | CLOCAL | CREAD);
+    termios.c_lflag &= ~(ISIG | ICANON | IEXTEN);
+    termios.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
+    termios.c_cc[VMIN] = 0;
+    termios.c_cc[VTIME] = 10;
+
+    ::cfsetospeed(&termios, B9600);
+    ::cfsetispeed(&termios, B9600);
+
+    if (::tcsetattr(m_fd, TCSANOW, &termios) < 0) {
+        ::LogError(LOG_HOST, "Cannot set the attributes for %s", m_port.c_str());
+        return false;
+    }
+#endif // !defined(_WIN32)
+
+    return true;
+}
+
+

src/bridge/CtsCorController.h

@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Digital Voice Modem - Bridge
+ * GPLv2 Open Source. Use is subject to license terms.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ *  Copyright (C) 2025 Lorenzo L. Romero, K2LLR
+ */
+/**
+ * @file CtsCorController.h
+ * @ingroup bridge
+ */
+#if !defined(__CTS_COR_CONTROLLER_H__)
+#define __CTS_COR_CONTROLLER_H__
+
+#include "Defines.h"
+#include "common/Log.h"
+
+#include <string>
+
+#if defined(_WIN32)
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#else
+#include <fcntl.h>
+#include <unistd.h>
+#include <termios.h>
+#include <sys/ioctl.h>
+#endif // defined(_WIN32)
+
+/**
+ * @brief This class implements CTS-based COR detection for the bridge.
+ * @ingroup bridge
+ */
+class HOST_SW_API CtsCorController {
+public:
+    /**
+     * @brief Initializes a new instance of the CtsCorController class.
+     * @param port Serial port device (e.g., /dev/ttyUSB0).
+     */
+    CtsCorController(const std::string& port);
+    /**
+     * @brief Finalizes a instance of the CtsCorController class.
+     */
+    ~CtsCorController();
+
+    /**
+     * @brief Opens the serial port for CTS readback.
+     * @param reuseFd Optional file descriptor to reuse (when sharing port with RTS PTT).
+     * @returns bool True, if port was opened successfully, otherwise false.
+     */
+    bool open(int reuseFd = -1);
+    /**
+     * @brief Closes the serial port.
+     */
+    void close();
+
+    /**
+     * @brief Reads the current CTS signal state.
+     * @returns bool True if CTS is asserted (active), otherwise false.
+     */
+    bool isCtsAsserted();
+
+private:
+    std::string m_port;
+    bool m_isOpen;
+    bool m_ownsFd; // true if we opened the fd, false if reusing from RTS PTT
+#if defined(_WIN32)
+    HANDLE m_fd;
+#else
+    int m_fd;
+#endif // defined(_WIN32)
+
+    /**
+     * @brief Sets the termios settings on the serial port.
+     * @returns bool True, if settings are set, otherwise false.
+     */
+    bool setTermios();
+};
+
+#endif // __CTS_COR_CONTROLLER_H__
+
+