srd: onewire_link: Cosmetics, simplifications, doc fixes.

2 files changed, 196 insertions, 157 deletions

diff --git a/decoders/onewire_link/__init__.py b/decoders/onewire_link/__init__.py
index 5c7251d..cb03471 100644
--- a/decoders/onewire_link/__init__.py
+++ b/decoders/onewire_link/__init__.py
@@ -19,63 +19,73 @@
 ##
 
 '''
-1-Wire protocol decoder.
+1-Wire protocol decoder (link layer).
 
-The 1-Wire protocol enables bidirectional communication over a single wire (and
-ground) between a single master and one or multiple slaves. The protocol is
-layered.
-- Link layer (reset, presence detection, reading/writing bits)
-- Network layer (skip/search/match device ROM addresses)
-- Transport layer (transport data between 1-Wire master and device)
+The 1-Wire protocol enables bidirectional communication over a single wire
+(and ground) between a single master and one or multiple slaves. The protocol
+is layered:
 
-Link layer
+ - Link layer (reset, presence detection, reading/writing bits)
+ - Network layer (skip/search/match device ROM addresses)
+ - Transport layer (transport data between 1-Wire master and device)
+
+Link layer protocol details:
 
 Sample rate:
-A high enough sample rate is required to properly detect all the elements of
-the protocol. A lower sample rate can be used if the master does not use
-overdrive communication speed. The next minimal values should be used:
-- overdrive     available:   2MHz minimum, 5MHz suggested
-- overdrive not available: 400kHz minimum, 1MHz suggested
+A sufficiently high samplerate is required to properly detect all the elements
+of the protocol. A lower samplerate can be used if the master does not use
+overdrive communication speed. The following minimal values should be used:
+
+ - overdrive available: 2MHz minimum, 5MHz suggested
+ - overdrive not available: 400kHz minimum, 1MHz suggested
 
 Probes:
 1-Wire requires a single signal, but some master implementations might have a
-separate signal use to deliver power to the bus during temperature conversion
-as an example. This power signal is currently not parsed.
-- owr (1-Wire bus)
-- pwr (1-Wire power)
+separate signal used to deliver power to the bus during temperature conversion
+as an example. This power signal is currently not used.
+
+ - owr (1-Wire signal line)
+ - pwr (optional, dedicated power supply pin)
 
 Options:
-1-Wire is an asynchronous protocol, so the decoder must know the sample rate.
-The timing for sampling bits, presence and reset is calculated by the decoder,
+1-Wire is an asynchronous protocol, so the decoder must know the samplerate.
+The timing for sampling bits, presence, and reset is calculated by the decoder,
 but in case the user wishes to use different values, it is possible to
-configure the next timing values (number of sample rate periods):
-- overdrive              (if active the decoder will be prepared for overdrive)
-- cnt_normal_bit         (time for normal mode sample bit)
-- cnt_normal_slot        (time for normal mode data slot)
-- cnt_normal_presence    (time for normal mode sample presence)
-- cnt_normal_reset       (time for normal mode reset)
-- cnt_overdrive_bit      (time for overdrive mode sample bit)
-- cnt_overdrive_slot     (time for overdrive mode data slot)
-- cnt_overdrive_presence (time for overdrive mode sample presence)
-- cnt_overdrive_reset    (time for overdrive mode reset)
-This options should be configured only on very rare cases and the user should
+configure the following timing values (number of samplerate periods):
+
+ - overdrive              (if active the decoder will be prepared for overdrive)
+ - cnt_normal_bit         (time for normal mode sample bit)
+ - cnt_normal_slot        (time for normal mode data slot)
+ - cnt_normal_presence    (time for normal mode sample presence)
+ - cnt_normal_reset       (time for normal mode reset)
+ - cnt_overdrive_bit      (time for overdrive mode sample bit)
+ - cnt_overdrive_slot     (time for overdrive mode data slot)
+ - cnt_overdrive_presence (time for overdrive mode sample presence)
+ - cnt_overdrive_reset    (time for overdrive mode reset)
+
+These options should be configured only on very rare cases and the user should
 read the decoder source code to understand them correctly.
 
+Protocol output format:
+TODO.
+
 Annotations:
-Link layer annotations show the next events:
-- NOTE/WARNING/ERROR
-  Possible sample rate related timing issues are reported.
-- RESET/PRESENCE True/False
-  The event is marked from the signal negative edge to the end of the reset
-  high period. It is also reported if there are any devices attached to the
-  bus.
-- BIT 0/1
-  The event is marked from the signal negative edge to the end of the data
-  slot. The value of each received bit is also provided.
+
+Link layer annotations show the following events:
+
+ - NOTE/WARNING/ERROR
+   Possible samplerate related timing issues are reported.
+ - Reset/presence true/false
+   The event is marked from the signal negative edge to the end of the reset
+   high period. It's also reported if there are any devices attached to the bus.
+ - Bit 0/1
+   The event is marked from the signal negative edge to the end of the data
+   slot. The value of each received bit is also provided.
 
 TODO:
-- check for protocol correctness, if events are timed inside prescribed limits
-- maybe add support for interrupts, check if this feature is deprecated
+- Check for protocol correctness, if events are timed inside prescribed limits.
+- Maybe add support for interrupts, check if this feature is deprecated.
 '''
 
-from .onewire_link    import *
+from .onewire_link import *
+
diff --git a/decoders/onewire_link/onewire_link.py b/decoders/onewire_link/onewire_link.py
index f4b7b30..d6aec2c 100644
--- a/decoders/onewire_link/onewire_link.py
+++ b/decoders/onewire_link/onewire_link.py
@@ -18,7 +18,7 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 ##
 
-# 1-Wire link layer protocol decoder
+# 1-Wire protocol decoder (link layer)
 
 import sigrokdecode as srd
 
@@ -26,7 +26,7 @@ class Decoder(srd.Decoder):
     api_version = 1
     id = 'onewire_link'
     name = '1-Wire link layer'
-    longname = '1-Wire serial communication bus'
+    longname = '1-Wire serial communication bus (link layer)'
     desc = 'Bidirectional, half-duplex, asynchronous serial bus.'
     license = 'gplv2+'
     inputs = ['logic']
@@ -38,200 +38,229 @@ class Decoder(srd.Decoder):
         {'id': 'pwr', 'name': 'PWR', 'desc': '1-Wire power'},
     ]
     options = {
-        'overdrive'             : ['Overdrive', 1],
-        'cnt_normal_bit'        : ['Time (in samplerate periods) for normal mode sample bit'     , 0],
-        'cnt_normal_slot'       : ['Time (in samplerate periods) for normal mode data slot'      , 0],
-        'cnt_normal_presence'   : ['Time (in samplerate periods) for normal mode sample presence', 0],
-        'cnt_normal_reset'      : ['Time (in samplerate periods) for normal mode reset'          , 0],
-        'cnt_overdrive_bit'     : ['Time (in samplerate periods) for overdrive mode sample bit'     , 0],
-        'cnt_overdrive_slot'    : ['Time (in samplerate periods) for overdrive mode data slot'      , 0],
-        'cnt_overdrive_presence': ['Time (in samplerate periods) for overdrive mode sample presence', 0],
-        'cnt_overdrive_reset'   : ['Time (in samplerate periods) for overdrive mode reset'          , 0],
+        'overdrive': ['Overdrive', 1],
+        # Time options (specified in number of samplerate periods):
+        'cnt_normal_bit': ['Normal mode sample bit time', 0],
+        'cnt_normal_slot': ['Normal mode data slot time', 0],
+        'cnt_normal_presence': ['Normal mode sample presence time', 0],
+        'cnt_normal_reset': ['Normal mode reset time', 0],
+        'cnt_overdrive_bit': ['Overdrive mode sample bit time', 0],
+        'cnt_overdrive_slot': ['Overdrive mode data slot time', 0],
+        'cnt_overdrive_presence': ['Overdrive mode sample presence time', 0],
+        'cnt_overdrive_reset': ['Overdrive mode reset time', 0],
     }
     annotations = [
         ['Link', 'Link layer events (reset, presence, bit slots)'],
     ]
 
     def __init__(self, **kwargs):
-        # Common variables
         self.samplenum = 0
         # Link layer variables
-        self.state   = 'WAIT FOR FALLING EDGE'
+        self.state = 'WAIT FOR FALLING EDGE'
         self.present = 0
-        self.bit     = 0
+        self.bit = 0
         self.bit_cnt = 0
         self.command = 0
         self.overdrive = 0
         # Event timing variables
-        self.fall    = 0
-        self.rise    = 0
+        self.fall = 0
+        self.rise = 0
 
     def start(self, metadata):
         self.out_proto = self.add(srd.OUTPUT_PROTO, 'onewire_link')
-        self.out_ann   = self.add(srd.OUTPUT_ANN  , 'onewire_link')
+        self.out_ann = self.add(srd.OUTPUT_ANN, 'onewire_link')
 
-        # check if samplerate is appropriate
         self.samplerate = metadata['samplerate']
-        if (self.options['overdrive']):
+
+        # Check if samplerate is appropriate.
+        if self.options['overdrive']:
             self.put(0, 0, self.out_ann, [0,
-              ['NOTE: Sample rate checks assume overdrive mode.']])
-            if   (self.samplerate < 2000000):
+                ['NOTE: Sample rate checks assume overdrive mode.']])
+            if self.samplerate < 2000000:
                 self.put(0, 0, self.out_ann, [0,
-                  ['ERROR: Sampling rate is too low must be above 2MHz for proper overdrive mode decoding.']])
-            elif (self.samplerate < 5000000):
+                    ['ERROR: Sampling rate is too low. Must be above 2MHz ' +
+                     'for proper overdrive mode decoding.']])
+            elif self.samplerate < 5000000:
                 self.put(0, 0, self.out_ann, [0,
-                  ['WARNING: Sampling rate is suggested to be above 5MHz for proper overdrive mode decoding.']])
+                  ['WARNING: Sampling rate is suggested to be above 5MHz ' +
+                   'for proper overdrive mode decoding.']])
         else:
             self.put(0, 0, self.out_ann, [0,
-              ['NOTE: Sample rate checks assume normal mode only.']])
-            if   (self.samplerate <  400000):
+                ['NOTE: Sample rate checks assume normal mode only.']])
+            if self.samplerate < 400000:
                 self.put(0, 0, self.out_ann, [0,
-                  ['ERROR: Sampling rate is too low must be above 400kHz for proper normal mode decoding.']])
+                    ['ERROR: Sampling rate is too low. Must be above ' +
+                     '400kHz for proper normal mode decoding.']])
             elif (self.samplerate < 1000000):
                 self.put(0, 0, self.out_ann, [0,
-                  ['WARNING: Sampling rate is suggested to be above 1MHz for proper normal mode decoding.']])
+                    ['WARNING: Sampling rate is suggested to be above ' +
+                     '1MHz for proper normal mode decoding.']])
 
-        # The default 1-Wire time base is 30us, this is used to calculate sampling times.
-        if (self.options['cnt_normal_bit']):
+        # The default 1-Wire time base is 30us. This is used to calculate
+        # sampling times.
+        samplerate = float(self.samplerate)
+        if self.options['cnt_normal_bit']:
             self.cnt_normal_bit = self.options['cnt_normal_bit']
         else:
-            self.cnt_normal_bit = int(float(self.samplerate) * 0.000015) - 1 # 15ns
-        if (self.options['cnt_normal_slot']):
+            self.cnt_normal_bit = int(samplerate * 0.000015) - 1 # 15ns
+        if self.options['cnt_normal_slot']:
             self.cnt_normal_slot = self.options['cnt_normal_slot']
         else:
-            self.cnt_normal_slot = int(float(self.samplerate) * 0.000060) - 1 # 60ns
-        if (self.options['cnt_normal_presence']):
+            self.cnt_normal_slot = int(samplerate * 0.000060) - 1 # 60ns
+        if self.options['cnt_normal_presence']:
             self.cnt_normal_presence = self.options['cnt_normal_presence']
         else:
-            self.cnt_normal_presence = int(float(self.samplerate) * 0.000075) - 1 # 75ns
-        if (self.options['cnt_normal_reset']):
+            self.cnt_normal_presence = int(samplerate * 0.000075) - 1 # 75ns
+        if self.options['cnt_normal_reset']:
             self.cnt_normal_reset = self.options['cnt_normal_reset']
         else:
-            self.cnt_normal_reset = int(float(self.samplerate) * 0.000480) - 1 # 480ns
-        if (self.options['cnt_overdrive_bit']):
+            self.cnt_normal_reset = int(samplerate * 0.000480) - 1 # 480ns
+        if self.options['cnt_overdrive_bit']:
             self.cnt_overdrive_bit = self.options['cnt_overdrive_bit']
         else:
-            self.cnt_overdrive_bit = int(float(self.samplerate) * 0.000002) - 1 # 2ns
-        if (self.options['cnt_overdrive_slot']):
+            self.cnt_overdrive_bit = int(samplerate * 0.000002) - 1 # 2ns
+        if self.options['cnt_overdrive_slot']:
             self.cnt_overdrive_slot = self.options['cnt_overdrive_slot']
         else:
-            self.cnt_overdrive_slot = int(float(self.samplerate) * 0.0000073) - 1 # 6ns+1.3ns
-        if (self.options['cnt_overdrive_presence']):
+            self.cnt_overdrive_slot = int(samplerate * 0.0000073) - 1 # 6ns+1.3ns
+        if self.options['cnt_overdrive_presence']:
             self.cnt_overdrive_presence = self.options['cnt_overdrive_presence']
         else:
-            self.cnt_overdrive_presence = int(float(self.samplerate) * 0.000010) - 1 # 10ns
-        if (self.options['cnt_overdrive_reset']):
+            self.cnt_overdrive_presence = int(samplerate * 0.000010) - 1 # 10ns
+        if self.options['cnt_overdrive_reset']:
             self.cnt_overdrive_reset = self.options['cnt_overdrive_reset']
         else:
-            self.cnt_overdrive_reset = int(float(self.samplerate) * 0.000048) - 1 # 48ns
+            self.cnt_overdrive_reset = int(samplerate * 0.000048) - 1 # 48ns
 
-        # organize values into lists
-        self.cnt_bit      = [self.cnt_normal_bit     , self.cnt_overdrive_bit     ]
+        # Organize values into lists.
+        self.cnt_bit = [self.cnt_normal_bit, self.cnt_overdrive_bit]
         self.cnt_presence = [self.cnt_normal_presence, self.cnt_overdrive_presence]
-        self.cnt_reset    = [self.cnt_normal_reset   , self.cnt_overdrive_reset   ]
-        self.cnt_slot     = [self.cnt_normal_slot    , self.cnt_overdrive_slot    ]
-
-        # Check if sample times are in the allowed range
-        time_min = float(self.cnt_normal_bit  ) / self.samplerate
-        time_max = float(self.cnt_normal_bit+1) / self.samplerate
-        if ( (time_min < 0.000005) or (time_max > 0.000015) ) :
-           self.put(0, 0, self.out_ann, [0,
-             ['WARNING: The normal mode data sample time interval (%2.1fus-%2.1fus) should be inside (5.0us, 15.0us).'
-               % (time_min*1000000, time_max*1000000)]])
-        time_min = float(self.cnt_normal_presence  ) / self.samplerate
-        time_max = float(self.cnt_normal_presence+1) / self.samplerate
-        if ( (time_min < 0.0000681) or (time_max > 0.000075) ) :
-           self.put(0, 0, self.out_ann, [0,
-             ['WARNING: The normal mode presence sample time interval (%2.1fus-%2.1fus) should be inside (68.1us, 75.0us).'
-               % (time_min*1000000, time_max*1000000)]])
-        time_min = float(self.cnt_overdrive_bit  ) / self.samplerate
-        time_max = float(self.cnt_overdrive_bit+1) / self.samplerate
-        if ( (time_min < 0.000001) or (time_max > 0.000002) ) :
-           self.put(0, 0, self.out_ann, [0,
-             ['WARNING: The overdrive mode data sample time interval (%2.1fus-%2.1fus) should be inside (1.0us, 2.0us).'
-               % (time_min*1000000, time_max*1000000)]])
-        time_min = float(self.cnt_overdrive_presence  ) / self.samplerate
-        time_max = float(self.cnt_overdrive_presence+1) / self.samplerate
-        if ( (time_min < 0.0000073) or (time_max > 0.000010) ) :
-           self.put(0, 0, self.out_ann, [0,
-             ['WARNING: The overdrive mode presence sample time interval (%2.1fus-%2.1fus) should be inside (7.3us, 10.0us).'
-               % (time_min*1000000, time_max*1000000)]])
+        self.cnt_reset = [self.cnt_normal_reset, self.cnt_overdrive_reset]
+        self.cnt_slot = [self.cnt_normal_slot, self.cnt_overdrive_slot]
+
+        # Check if sample times are in the allowed range.
+
+        time_min = float(self.cnt_normal_bit) / self.samplerate
+        time_max = float(self.cnt_normal_bit + 1) / self.samplerate
+        if (time_min < 0.000005) or (time_max > 0.000015):
+            self.put(0, 0, self.out_ann, [0,
+                ['WARNING: The normal mode data sample time interval ' +
+                 '(%2.1fus-%2.1fus) should be inside (5.0us, 15.0us).'
+                 % (time_min * 1000000, time_max * 1000000)]])
+
+        time_min = float(self.cnt_normal_presence) / self.samplerate
+        time_max = float(self.cnt_normal_presence + 1) / self.samplerate
+        if (time_min < 0.0000681) or (time_max > 0.000075):
+            self.put(0, 0, self.out_ann, [0,
+                ['WARNING: The normal mode presence sample time interval ' +
+                 '(%2.1fus-%2.1fus) should be inside (68.1us, 75.0us).'
+                 % (time_min * 1000000, time_max * 1000000)]])
+
+        time_min = float(self.cnt_overdrive_bit) / self.samplerate
+        time_max = float(self.cnt_overdrive_bit + 1) / self.samplerate
+        if (time_min < 0.000001) or (time_max > 0.000002):
+            self.put(0, 0, self.out_ann, [0,
+                ['WARNING: The overdrive mode data sample time interval ' +
+                 '(%2.1fus-%2.1fus) should be inside (1.0us, 2.0us).'
+                 % (time_min * 1000000, time_max * 1000000)]])
+
+        time_min = float(self.cnt_overdrive_presence) / self.samplerate
+        time_max = float(self.cnt_overdrive_presence + 1) / self.samplerate
+        if (time_min < 0.0000073) or (time_max > 0.000010):
+            self.put(0, 0, self.out_ann, [0,
+                ['WARNING: The overdrive mode presence sample time interval ' +
+                 '(%2.1fus-%2.1fus) should be inside (7.3us, 10.0us).'
+                 % (time_min*1000000, time_max*1000000)]])
 
     def report(self):
         pass
 
     def decode(self, ss, es, data):
         for (self.samplenum, (owr, pwr)) in data:
-
             # State machine.
             if self.state == 'WAIT FOR FALLING EDGE':
                 # The start of a cycle is a falling edge.
-                if (owr == 0):
+                if owr == 0:
                     # Save the sample number for the falling edge.
                     self.fall = self.samplenum
-                    # Go to waiting for sample time
+                    # Go to waiting for sample time.
                     self.state = 'WAIT FOR DATA SAMPLE'
             elif self.state == 'WAIT FOR DATA SAMPLE':
-                # Sample data bit
-                if (self.samplenum - self.fall == self.cnt_bit[self.overdrive]):
-                    self.bit  = owr
+                # Sample data bit.
+                t = self.samplenum - self.fall
+                if t == self.cnt_bit[self.overdrive]:
+                    self.bit = owr
                     self.state = 'WAIT FOR DATA SLOT END'
             elif self.state == 'WAIT FOR DATA SLOT END':
-                # A data slot ends in a recovery period, otherwise, this is probably a reset
-                if (self.samplenum - self.fall == self.cnt_slot[self.overdrive]):
-                    if (owr):
-                        self.put(self.fall, self.samplenum, self.out_ann, [0, ['BIT: %01x' % self.bit]])
-                        self.put(self.fall, self.samplenum, self.out_proto, ['BIT', self.bit])
-                        # Checking the first command to see if overdrive mode should be entered
-                        if   (self.bit_cnt <= 8):
-                            self.command = self.command | (self.bit << self.bit_cnt)
-                        elif (self.bit_cnt == 8):
-                            if (self.command in [0x3c, 0x69]):
-                                self.put(self.fall, self.cnt_bit[self.overdrive], self.out_ann, [0, ['ENTER OVERDRIVE MODE']])
-                        # Incrementing the bit counter
+                # A data slot ends in a recovery period, otherwise, this is
+                # probably a reset.
+                t = self.samplenum - self.fall
+                if t == self.cnt_slot[self.overdrive]:
+                    if owr:
+                        self.put(self.fall, self.samplenum, self.out_ann,
+                                 [0, ['BIT: %01x' % self.bit]])
+                        self.put(self.fall, self.samplenum, self.out_proto,
+                                 ['BIT', self.bit])
+
+                        # Checking the first command to see if overdrive mode
+                        # should be entered.
+                        if self.bit_cnt <= 8:
+                            self.command |= (self.bit << self.bit_cnt)
+                        elif self.bit_cnt == 8 and self.command in [0x3c, 0x69]:
+                            self.put(self.fall, self.cnt_bit[self.overdrive],
+                                     self.out_ann,
+                                     [0, ['ENTER OVERDRIVE MODE']])
+                        # Increment the bit counter.
                         self.bit_cnt += 1
-                        # Wait for next slot
+                        # Wait for next slot.
                         self.state = 'WAIT FOR FALLING EDGE'
                     else:
-                        # This seems to be a reset slot, wait for its end
+                        # This seems to be a reset slot, wait for its end.
                         self.state = 'WAIT FOR RISING EDGE'
             elif self.state == 'WAIT FOR RISING EDGE':
                 # The end of a cycle is a rising edge.
-                if (owr):
-                    # Check if this was a reset cycle
-                    if (self.samplenum - self.fall > self.cnt_normal_reset):
+                if owr:
+                    # Check if this was a reset cycle.
+                    t = self.samplenum - self.fall
+                    if t > self.cnt_normal_reset:
                         # Save the sample number for the falling edge.
                         self.rise = self.samplenum
-                        self.state = "WAIT FOR PRESENCE DETECT"
-                        # Exit overdrive mode
-                        if (self.overdrive):
-                            self.put(self.fall, self.cnt_bit[self.overdrive], self.out_ann, [0, ['EXIT OVERDRIVE MODE']])
+                        self.state = 'WAIT FOR PRESENCE DETECT'
+                        # Exit overdrive mode.
+                        if self.overdrive:
+                            self.put(self.fall, self.cnt_bit[self.overdrive],
+                                     self.out_ann, [0, ['EXIT OVERDRIVE MODE']])
                             self.overdrive = 0
-                        # Clear command bit counter and data register
+                        # Clear command bit counter and data register.
                         self.bit_cnt = 0
                         self.command = 0
-                    elif ((self.samplenum - self.fall > self.cnt_overdrive_reset) and (self.overdrive)):
+                    elif (t > self.cnt_overdrive_reset) and self.overdrive:
                         # Save the sample number for the falling edge.
                         self.rise = self.samplenum
                         self.state = "WAIT FOR PRESENCE DETECT"
                     # Otherwise this is assumed to be a data bit.
-                    else :
+                    else:
                         self.state = "WAIT FOR FALLING EDGE"
             elif self.state == 'WAIT FOR PRESENCE DETECT':
-                # Sample presence status
-                if (self.samplenum - self.rise == self.cnt_presence[self.overdrive]):
+                # Sample presence status.
+                t = self.samplenum - self.rise
+                if t == self.cnt_presence[self.overdrive]:
                     self.present = owr
                     self.state = 'WAIT FOR RESET SLOT END'
             elif self.state == 'WAIT FOR RESET SLOT END':
                 # A reset slot ends in a long recovery period
-                if (self.samplenum - self.rise == self.cnt_reset[self.overdrive]):
-                    if (owr):
-                        self.put(self.fall, self.samplenum, self.out_ann, [0, ['RESET/PRESENCE: %s' % ('False' if self.present else 'True')]])
-                        self.put(self.fall, self.samplenum, self.out_proto, ['RESET/PRESENCE', not self.present])
-                        # Wait for next slot
+                t = self.samplenum - self.rise
+                if t == self.cnt_reset[self.overdrive]:
+                    if owr:
+                        self.put(self.fall, self.samplenum, self.out_ann,
+                                 [0, ['RESET/PRESENCE: %s'
+                                 % ('False' if self.present else 'True')]])
+                        self.put(self.fall, self.samplenum, self.out_proto,
+                                 ['RESET/PRESENCE', not self.present])
+                        # Wait for next slot.
                         self.state = 'WAIT FOR FALLING EDGE'
                     else:
-                        # This seems to be a reset slot, wait for its end
+                        # This seems to be a reset slot, wait for its end.
                         self.state = 'WAIT FOR RISING EDGE'
             else:
-                raise Exception('Invalid state: %d' % self.state)
+                raise Exception('Invalid state: %s' % self.state)