Add support for newer SIMCom devices

This patch adds support to event driven calls for newer SIMCom devices
such as the SIM7100, SIM7500, and SIM7600.

These devices support the command "AT+CLCC=1" which sets the modem to
print the CLCC output on every call status change. I made an effort to
to probe modem upport for automatic reporting by trying setting AT+CLCC
to 1. The untested assumption is that the command will fail if the modem
does not support it.

The regular expressions used for _handleCallAnswered,
_handleCallInitiated, and _handleCallEnded are simply a copy and paste
from the regular expression used for CLCC, replacing what was on the
third group by a fixed number representing the call status. For example,
using the number 6 to indicate that the call was disconnected.

To detect the newer devices I used the availability of the +SIMCOMATI
command but I am not really sure how reliable this is. My concern is of
false positives for devices that could support the +SIMCOMATI and not
support the automatic reporting of "AT+CLCC=1".

This was tested on an SIM7600G.

Signed-off-by: Peter Senna Tschudin <[email protected]>

gsmmodem/modem.py

@@ -255,6 +255,8 @@ def connect(self, pin=None, waitingForModemToStartInSeconds=0):
                 enableWind = True
             elif '+ZPAS' in commands:
                 callUpdateTableHint = 3 # ZTE
+            if '+SIMCOMATI' in commands:
+                callUpdateTableHint = 4 # SIMCom
         else:
             # Try to enable general notifications on Wavecom-like device
             enableWind = True
@@ -323,6 +325,38 @@ def connect(self, pin=None, waitingForModemToStartInSeconds=0):
             self._waitForCallInitUpdate = False # ZTE modems do not provide "call initiated" updates
             if commands == None: # ZTE uses standard +VTS for DTMF
                 Call.dtmfSupport = True
+        elif callUpdateTableHint == 4: # SIMCom (Tested on SIM7600)
+            self.log.info('Loading SIMCOM call state update table')
+            self._mustPollCallStatus = False
+            Call.dtmfSupport = True
+            try:
+                # Enables automatic reporting of the list of current calls
+                # when the call status changes
+                self.write('AT+CLCC=1')
+            except CommandError:
+                # Modem does not support automatic reporting of the list of
+                # current calls when the call status changes
+                self.log.info('Will use polling for call state updates')
+                self._mustPollCallStatus = True
+
+            # This works well with the SIM7600G for example
+            if not self._mustPollCallStatus:
+                # Using the field <stat> of the AT+CLCC command. Notice the
+                # numbers between groups 1 and 2 on the following regexes
+                #
+                # The possible values are:
+                #   0 – active
+                #   1 – held
+                #   2 – dialing (MO call)
+                #   3 – alerting (MO call)
+                #   4 – incoming (MT call)
+                #   5 – waiting (MT call)
+                #   6 – disconnect
+                self._callStatusUpdates = (
+                    (re.compile('^\+CLCC:\s+\d+,\d,0,\d,[^,],"([^,]*)",\d+$'), self._handleCallAnswered),
+                    (re.compile('^\+CLCC:\s+\d+,\d,2,\d,[^,],"([^,]*)",\d+$'), self._handleCallInitiated),
+                    (re.compile('^\+CLCC:\s+\d+,\d,6,\d,[^,],"([^,]*)",\d+$'), self._handleCallEnded),
+                    (re.compile('^BUSY$'), self._handleCallRejected))
         else:
             # Unknown modem - we do not know what its call updates look like. Use polling instead
             self.log.info('Unknown/generic modem type - will use polling for call state updates')
@@ -567,7 +601,7 @@ def supportedCommands(self):
         except (TimeoutException, CommandError):
             # Try interactive command recognition
             commands = []
-            checkable_commands = ['^CVOICE', '+VTS', '^DTMF', '^USSDMODE', '+WIND', '+ZPAS', '+CSCS', '+CNUM']
+            checkable_commands = ['^CVOICE', '+VTS', '^DTMF', '^USSDMODE', '+WIND', '+ZPAS', '+CSCS', '+CNUM', '+SIMCOMATI']
 
             # Check if modem is still alive
             try: