uart: add FRAME Python annotation, communicate frame validity

Internally keep track of the UART frame's validity. Emit a FRAME Python
annotation for aborted as well as for completed frames. This obsoletes a
TODO comment in the STOP bit code path.

This annotation also spans the complete frame's length, including start
and parity and stop bits, which the DATA annotation doesn't cover.
Stacked decoders can individually decide whether to strictly reference
the mere data bits section or the complete UART frame which happened to
communicate the data value.

1 files changed, 16 insertions, 1 deletions

diff --git a/decoders/uart/pd.py b/decoders/uart/pd.py
index 2ba8c57..f89c6e5 100644
--- a/decoders/uart/pd.py
+++ b/decoders/uart/pd.py
@@ -41,6 +41,9 @@ This is the list of <ptype>s and their respective <pdata> values:
    the expected parity value, the second is the actual parity value.
  - TODO: Frame error?
  - 'BREAK': The data is always 0.
+ - 'FRAME': The data is always a tuple containing two items: The (integer)
+   value of the UART data, and a boolean which reflects the validity of the
+   UART frame.
 
 The <rxtx> field is 0 for RX packets, 1 for TX packets.
 '''
@@ -178,6 +181,7 @@ class Decoder(srd.Decoder):
         self.samplerate = None
         self.samplenum = 0
         self.frame_start = [-1, -1]
+        self.frame_valid = [None, None]
         self.startbit = [-1, -1]
         self.cur_data_bit = [0, 0]
         self.datavalue = [0, 0]
@@ -214,6 +218,7 @@ class Decoder(srd.Decoder):
     def wait_for_start_bit(self, rxtx, signal):
         # Save the sample number where the start bit begins.
         self.frame_start[rxtx] = self.samplenum
+        self.frame_valid[rxtx] = True
 
         self.state[rxtx] = 'GET START BIT'
 
@@ -225,6 +230,10 @@ class Decoder(srd.Decoder):
         if self.startbit[rxtx] != 0:
             self.putp(['INVALID STARTBIT', rxtx, self.startbit[rxtx]])
             self.putg([rxtx + 10, ['Frame error', 'Frame err', 'FE']])
+            self.frame_valid[rxtx] = False
+            es = self.samplenum + ceil(self.bit_width / 2.0)
+            self.putpse(self.frame_start[rxtx], es, ['FRAME', rxtx,
+                (self.datavalue[rxtx], self.frame_valid[rxtx])])
             self.state[rxtx] = 'WAIT FOR START BIT'
             return
 
@@ -331,6 +340,7 @@ class Decoder(srd.Decoder):
             # TODO: Return expected/actual parity values.
             self.putp(['PARITY ERROR', rxtx, (0, 1)]) # FIXME: Dummy tuple...
             self.putg([rxtx + 6, ['Parity error', 'Parity err', 'PE']])
+            self.frame_valid[rxtx] = False
 
         self.state[rxtx] = 'GET STOP BITS'
 
@@ -342,11 +352,16 @@ class Decoder(srd.Decoder):
         if self.stopbit1[rxtx] != 1:
             self.putp(['INVALID STOPBIT', rxtx, self.stopbit1[rxtx]])
             self.putg([rxtx + 10, ['Frame error', 'Frame err', 'FE']])
-            # TODO: Abort? Ignore the frame? Other?
+            self.frame_valid[rxtx] = False
 
         self.putp(['STOPBIT', rxtx, self.stopbit1[rxtx]])
         self.putg([rxtx + 4, ['Stop bit', 'Stop', 'T']])
 
+        # Pass the complete UART frame to upper layers.
+        es = self.samplenum + ceil(self.bit_width / 2.0)
+        self.putpse(self.frame_start[rxtx], es, ['FRAME', rxtx,
+            (self.datavalue[rxtx], self.frame_valid[rxtx])])
+
         self.state[rxtx] = 'WAIT FOR START BIT'
 
     def handle_break(self, rxtx):