Cellular: added setting of data carrier support for UART.

Author: Teppo Järvelin

UNITTESTS/features/cellular/framework/AT/at_cellularcontext/unittest.cmake

@@ -38,4 +38,6 @@ set(unittest-test-sources
   stubs/randLIB_stub.cpp
   stubs/Semaphore_stub.cpp
   stubs/us_ticker_stub.cpp
+  stubs/UARTSerial_stub.cpp
+  stubs/SerialBase_stub.cpp
 )

UNITTESTS/stubs/AT_CellularContext_stub.cpp

@@ -42,6 +42,14 @@ AT_CellularContext::~AT_CellularContext()
 {
 }
 
+void AT_CellularContext::set_file_handle(UARTSerial *serial, PinName dcd_pin, bool active_high)
+{
+}
+
+void AT_CellularContext::enable_hup(bool enable)
+{
+}
+
 void AT_CellularContext::set_file_handle(FileHandle *fh)
 {
 }

UNITTESTS/stubs/AT_CellularDevice_stub.cpp

@@ -64,7 +64,12 @@ nsapi_error_t AT_CellularDevice::release_at_handler(ATHandler *at_handler)
     }
 }
 
-CellularContext *create_context(FileHandle *fh = NULL, const char *apn = MBED_CONF_NSAPI_DEFAULT_CELLULAR_APN)
+CellularContext *AT_CellularDevice::create_context(UARTSerial *serial, const char *const apn, PinName dcd_pin,
+                                                   bool active_high)
+{
+}
+
+CellularContext *create_context(FileHandle *fh, const char *apn)
 {
 }
 

UNITTESTS/target_h/myCellularDevice.h

@@ -52,6 +52,12 @@ class myCellularDevice : public CellularDevice {
         return NSAPI_ERROR_OK;
     }
 
+    virtual CellularContext *create_context(UARTSerial *serial, const char *const apn, PinName dcd_pin,
+                                                   bool active_high)
+    {
+        return NULL;
+    }
+
     virtual CellularContext *create_context(FileHandle *fh = NULL, const char *apn = NULL)
     {
         EventQueue que;

features/cellular/framework/API/CellularContext.h

@@ -107,7 +107,6 @@ class CellularContext : public CellularBase {
     // friend of CellularDevice, so it's the only way to close or delete this class.
     friend class CellularDevice;
     virtual ~CellularContext() {}
-
 public: // from NetworkInterface
     virtual nsapi_error_t set_blocking(bool blocking) = 0;
     virtual NetworkStack *get_stack() = 0;
@@ -227,6 +226,15 @@ class CellularContext : public CellularBase {
      */
     virtual void set_file_handle(FileHandle *fh) = 0;
 
+    /** Set the UART serial used to communicate with the modem. Can be used to change default file handle.
+     *  File handle set with this method will use data carrier detect to be able to detect disconnection much faster in PPP mode.
+     *
+     *  @param serial       UARTSerial used in communication to modem. If null then the default file handle is used.
+     *  @param dcd_pin      Pin used to set data carrier detect on/off for the given UART
+     *  @param active_high  a boolean set to true if DCD polarity is active low
+     */
+    virtual void set_file_handle(UARTSerial *serial, PinName dcd_pin = NC, bool active_high = false) = 0;
+
 protected: // Device specific implementations might need these so protected
     enum ContextOperation {
         OP_INVALID      = -1,
@@ -245,6 +253,15 @@ class CellularContext : public CellularBase {
     */
     virtual void cellular_callback(nsapi_event_t ev, intptr_t ptr) = 0;
 
+    /** Enable or disable hang-up detection
+     *
+     *  When in PPP data pump mode, it is helpful if the FileHandle will signal hang-up via
+     *  POLLHUP, e.g., if the DCD line is deasserted on a UART. During command mode, this
+     *  signaling is not desired. enable_hup() controls whether this function should be
+     *  active.
+     */
+    virtual void enable_hup(bool enable) = 0;
+
     // member variables needed in target override methods
     NetworkStack *_stack; // must be pointer because of PPP
     nsapi_ip_stack_t _ip_stack_type;
@@ -259,6 +276,8 @@ class CellularContext : public CellularBase {
     const char *_apn;
     const char *_uname;
     const char *_pwd;
+    PinName _dcd_pin;
+    bool _active_high;
 };
 
 /**

features/cellular/framework/API/CellularDevice.h

@@ -22,6 +22,7 @@
 #include "CellularStateMachine.h"
 #include "Callback.h"
 #include "ATHandler.h"
+#include "UARTSerial.h"
 
 namespace mbed {
 
@@ -102,6 +103,21 @@ class CellularDevice {
      */
     virtual CellularContext *create_context(FileHandle *fh = NULL, const char *apn = NULL) = 0;
 
+    /** Creates a new CellularContext interface. This API should be used if serial is UART and PPP mode used.
+     *  CellularContext created will use data carrier detect to be able to detect disconnection much faster in PPP mode.
+     *  UARTSerial usually is the same which was given for the CellularDevice.
+     *
+     *  @param serial       UARTSerial used in communication to modem. If null then the default file handle is used.
+     *  @param apn          access point to use with context, can be null.
+     *  @param dcd_pin      Pin used to set data carrier detect on/off for the given UART
+     *  @param active_high  a boolean set to true if DCD polarity is active low
+     *
+     *  @return         new instance of class CellularContext or NULL in case of failure
+     *
+     */
+    virtual CellularContext *create_context(UARTSerial *serial, const char *apn, PinName dcd_pin = NC,
+                                            bool active_high = false) = 0;
+
     /** Deletes the given CellularContext instance
      *
      *  @param context CellularContext to delete
@@ -113,6 +129,12 @@ class CellularDevice {
      */
     void stop();
 
+    /** Get the current FileHandle item used when communicating with the modem.
+     *
+     *  @return reference to FileHandle
+     */
+    FileHandle &get_file_handle() const;
+
     /** Get event queue that can be chained to main event queue.
      *  @return event queue
      */

features/cellular/framework/AT/ATHandler.cpp

@@ -154,6 +154,10 @@ void ATHandler::set_file_handle(FileHandle *fh)
 void ATHandler::set_is_filehandle_usable(bool usable)
 {
     _is_fh_usable = usable;
+    if (usable) {
+        // set file handle sigio and blocking mode back
+        set_file_handle(_fileHandle);
+    }
 }
 
 void ATHandler::set_urc_handler(const char *prefix, Callback<void()> callback)

features/cellular/framework/AT/AT_CellularContext.cpp

@@ -59,11 +59,13 @@ AT_CellularContext::AT_CellularContext(ATHandler &at, CellularDevice *device, co
     _cid = -1;
     _new_context_set = false;
     _next = NULL;
+    _dcd_pin = NC;
+    _active_high = false;
 }
 
 AT_CellularContext::~AT_CellularContext()
 {
-    tr_info("Delete CellularContext %s (%p)", _apn ? _apn : "", this);
+    tr_info("Delete CellularContext with apn: [%s] (%p)", _apn ? _apn : "", this);
 
     (void)disconnect();
 
@@ -79,6 +81,23 @@ void AT_CellularContext::set_file_handle(FileHandle *fh)
     _at.set_file_handle(_fh);
 }
 
+void AT_CellularContext::set_file_handle(UARTSerial *serial, PinName dcd_pin, bool active_high)
+{
+    tr_info("CellularContext serial %p", serial);
+    _dcd_pin = dcd_pin;
+    _active_high = active_high;
+    _fh = serial;
+    _at.set_file_handle(static_cast<FileHandle *>(serial));
+    enable_hup(false);
+}
+
+void AT_CellularContext::enable_hup(bool enable)
+{
+    if (_dcd_pin != NC) {
+        static_cast<UARTSerial *>(_fh)->set_data_carrier_detect(enable ? _dcd_pin : NC, _active_high);
+    }
+}
+
 nsapi_error_t AT_CellularContext::connect()
 {
     tr_info("CellularContext connect");
@@ -595,18 +614,25 @@ nsapi_error_t AT_CellularContext::open_data_channel()
     }
 
     _at.set_is_filehandle_usable(false);
-
+    enable_hup(true);
     /* Initialize PPP
      * If blocking: mbed_ppp_init() is a blocking call, it will block until
                   connected, or timeout after 30 seconds*/
-    return nsapi_ppp_connect(_at.get_file_handle(), callback(this, &AT_CellularContext::ppp_status_cb), _uname, _pwd, _ip_stack_type);
+    nsapi_error_t err = nsapi_ppp_connect(_at.get_file_handle(), callback(this, &AT_CellularContext::ppp_status_cb), _uname, _pwd, _ip_stack_type);
+    if (err) {
+        ppp_disconnected();
+    }
+
+    return err;
 }
 
 void AT_CellularContext::ppp_status_cb(nsapi_event_t ev, intptr_t ptr)
 {
     tr_debug("ppp_status_cb: event %d, ptr %d", ev, ptr);
     if (ev == NSAPI_EVENT_CONNECTION_STATUS_CHANGE && ptr == NSAPI_STATUS_GLOBAL_UP) {
         _is_connected = true;
+    } else if (ev == NSAPI_EVENT_CONNECTION_STATUS_CHANGE && ptr == NSAPI_STATUS_DISCONNECTED) {
+        ppp_disconnected();
     } else {
         _is_connected = false;
     }
@@ -617,6 +643,20 @@ void AT_CellularContext::ppp_status_cb(nsapi_event_t ev, intptr_t ptr)
     _device->cellular_callback(ev, ptr);
 }
 
+void AT_CellularContext::ppp_disconnected()
+{
+    enable_hup(false);
+
+    // after ppp disconnect if we wan't to use same at handler we need to set filehandle again to athandler so it
+    // will set the correct sigio and nonblocking
+    _at.lock();
+    _at.set_is_filehandle_usable(true);
+    if (!_at.sync(AT_SYNC_TIMEOUT)) { // consume extra characters after ppp disconnect, also it may take a while until modem listens AT commands
+        tr_error("AT sync failed after PPP Disconnect");
+    }
+    _at.unlock();
+}
+
 #endif //#if NSAPI_PPP_AVAILABLE
 
 nsapi_error_t AT_CellularContext::disconnect()
@@ -631,15 +671,7 @@ nsapi_error_t AT_CellularContext::disconnect()
         tr_error("CellularContext disconnect failed!");
         // continue even in failure due to ppp disconnect in any case releases filehandle
     }
-    // after ppp disconnect if we wan't to use same at handler we need to set filehandle again to athandler so it
-    // will set the correct sigio and nonblocking
-    _at.lock();
-    _at.set_file_handle(_at.get_file_handle());
-    _at.set_is_filehandle_usable(true);
-    if (!_at.sync(AT_SYNC_TIMEOUT)) { // consume extra characters after ppp disconnect, also it may take a while until modem listens AT commands
-        tr_error("AT sync failed after PPP Disconnect");
-    }
-    _at.unlock();
+    ppp_disconnected();
 #endif // NSAPI_PPP_AVAILABLE
     _at.lock();
 

features/cellular/framework/AT/AT_CellularContext.h

@@ -57,6 +57,8 @@ class AT_CellularContext : public CellularContext, public AT_CellularBase {
     virtual nsapi_error_t register_to_network();
     virtual nsapi_error_t attach_to_network();
     virtual void set_file_handle(FileHandle *fh);
+    virtual void set_file_handle(UARTSerial *serial, PinName dcd_pin = NC, bool active_high = false);
+    virtual void enable_hup(bool enable);
 
 protected:
     virtual void cellular_callback(nsapi_event_t ev, intptr_t ptr);
@@ -93,6 +95,7 @@ class AT_CellularContext : public CellularContext, public AT_CellularBase {
 #if NSAPI_PPP_AVAILABLE
     nsapi_error_t open_data_channel();
     void ppp_status_cb(nsapi_event_t ev, intptr_t ptr);
+    void ppp_disconnected();
 #endif // #if NSAPI_PPP_AVAILABLE
     nsapi_error_t do_activate_context();
     bool set_new_context(int cid);

features/cellular/framework/AT/AT_CellularDevice.cpp

@@ -167,6 +167,17 @@ CellularContext *AT_CellularDevice::get_context_list() const
     return _context_list;
 }
 
+CellularContext *AT_CellularDevice::create_context(UARTSerial *serial, const char *const apn, PinName dcd_pin,
+                                                   bool active_high)
+{
+    // Call FileHandle base version - explict upcast to avoid recursing into ourselves
+    CellularContext *ctx = create_context(static_cast<FileHandle *>(serial), apn);
+    if (serial) {
+        ctx->set_file_handle(serial, dcd_pin, active_high);
+    }
+    return ctx;
+}
+
 CellularContext *AT_CellularDevice::create_context(FileHandle *fh, const char *apn)
 {
     AT_CellularContext *ctx = create_context_impl(*get_at_handler(fh), apn);