diff -r aa3d55f78563 -r 3b50c46fca56 gpib.py
--- a/gpib.py	Tue Dec 11 00:07:54 2007 +0100
+++ b/gpib.py	Fri Dec 14 00:21:47 2007 +0100
@@ -9,15 +9,138 @@
 class ConnectionError(Exception):
     pass
 
+GPIB_CONTROLLER = 1
+GPIB_DEVICE = 0
+
+# IEEE 488.2 Status Byte constants
+MAV = 0x10 # Message AVailable: bit 4 of the Status Byte
+ESB = 0x20 # Event Status Bit: bit 5 of the Status Byte
+MSS = 0x40 # Master Summary Status bit: bit 6 of the Status Byte (NOT
+           # sent in response to a serial poll)
+RQS = 0x40 # Request Service: bit 6 of the Status Byte (when sent in
+           # response to a serial poll)
+
+# SESR constants (Standard Event Status Register)
+PON = 0x80 # Power On: Power has been turned On since last register
+           # read access
+URQ = 0x40 # User Request: the user has activated some device control
+           # (whatever the Remote Local state is)
+CME = 0x20 # Command Error
+EXE = 0x10 # Execution Error
+DDE = 0x08 # Device Dependant Error
+QYE = 0x04 # QuerY Error (attempt to read data while Output Queue is
+           # empty, or data in the OQ was lost)
+RQC = 0x02 # Request Control: tell the CiC that the device wants to
+           # become the CiC
+OPC = 0x01 # Operation Complete: device has completed any pending
+           # operation (ready to accept new commands). This bit is
+           # generated in response to a OPC command.
+
+#####################
+# HP3562A constants
+
+# GPIB buffer size is 3x80 characters lines
+
+# HP3562A Status Byte
+RQS = 0x40 # Request Service: when sent in response to a serial poll
+ERR = 0x20 # ERRor: GPIB error
+RDY = 0x10 #ReaDY: ready to accept GPIB commands
+
+
 class GPIB(object):
     _retries = 15
     def __init__(self, device="/dev/ttyUSB0", baudrate=115200, timeout=0.1,
                     address=0, mode=1):        
+        """
+        Create a new GPIB controller for the Prologix USB-GPIB device
+        located on serial device 'device'.        
+        """
         self._cnx = serial.Serial(port=device, baudrate=baudrate, timeout=timeout)
         self._timeout = timeout
         
         self.set_mode(mode)
         self.set_address(address)
+        
+    def set_address(self, address):
+        """
+        Set the address of the GPIB device:
+        
+        - if the device is the Controller In Charge, this is the
+          address of the device commands are sent to,
+
+        - if the device is in GPIB_DEVICE mode, this is its address.
+        """
+        self._set_cmd('addr', address)
+        self._adress = address
+        
+    def set_mode(self, mode):
+        """
+        Set GPIB device mode to 'mode':
+        
+        - GPIB_CONTROLLER: set the device as the Controller In Charge
+          on the GPIB bus
+
+        - GPIB_DEVICE: set the device as a standard GPIB device on the
+          bus.
+        """
+        self._set_cmd('mode', mode)
+        self._mode = mode
+
+    def set_controler(self):
+        """
+        Set GPIB device the Controller In Charge on the GPIB bus.
+        """
+        self.set_mode(1)
+
+    def set_device(self):
+        """
+        Set the GPIB device as a simple device on the GPIB bus.        
+        """
+        self.set_mode(0)
+
+    def send_command(self, cmd):
+        """
+        Send the specified GPIB command on the bus (must be the CIC),
+        and read the answer.
+        """
+        assert self._mode == 1
+        self._cnx.write(cmd+'\r')
+        time.sleep(self._timeout) # required?
+        ret = self._cnx.readlines()
+        return ''.join(ret)
+
+    def check_srq(self):
+        """
+        Check the SRQ line
+        """
+        assert self._mode == 1, "must be the Controller In Charge"
+        self._cnx.write('++srq\r')
+        ret = self._cnx.readline().strip()
+        if ret:
+            return bool(int(ret))
+        return None
+
+    def poll(self):
+        """
+        Poll every address, and return a dictionnary
+         {add: status, ...}        
+        """
+        assert self._mode == 1, "must be the Controller In Charge"
+        dico = {}
+        for add in range(31):
+            self._cnx.write('++spoll %d\r'%i)
+            ret = self._cnx.readline().strip()
+            if ret:
+                dico[i] = int(ret)
+        return dico
+    
+    def _read(self):
+        for i in range(self._retries):
+            rdata = self._cnx.readline()
+            if rdata.strip() != "":
+                break
+            time.sleep(self._timeout)
+        return rdata
 
     def _set_cmd(self, cmd, value):
         self._cnx.write('++%s %d\r'%(cmd, value))
@@ -25,19 +148,4 @@
         rval = self._read().strip()
         if not rval.isdigit() or int(rval) != value:
             raise ConnectionError("Can't set GPIB %s to %s [ret=%s]"%(cmd, value, repr(rval)))
-        
-    def set_address(self, address):        
-        self._set_cmd('addr', address)
-        self._adress = address
-        
-    def set_mode(self, mode):
-        self._set_cmd('mode', mode)
-        self._mode = mode
-        
-    def _read(self):
-        for i in range(self._retries):
-            rdata = self._cnx.readline()
-            if rdata.strip() != "":
-                break
-            time.sleep(self._timeout)
-        return rdata
+