spi: Tell stacked decoders about missing CS# signal.

[libsigrokdecode.git] / decoders / spi / pd.py

diff --git a/decoders/spi/pd.py b/decoders/spi/pd.py
index 97d5571c066a3d8ec6664de9ef04cc766b4d756b..25a9f85f9c059b662fefd203f7e364fdd0edfbb2 100644 (file)
--- a/decoders/spi/pd.py
+++ b/decoders/spi/pd.py
@@ -35,7 +35,9 @@ Packet:
  - 'BITS': <data1>/<data2> contain a list of bit values in this MOSI/MISO data
    item, and for each of those also their respective start-/endsample numbers.
  - 'CS CHANGE': <data1> is the old CS# pin value, <data2> is the new value.
-   Both data items are Python numbers (0/1), not strings.
+   Both data items are Python numbers (0/1), not strings. At the beginning of
+   the decoding a packet is generated with <data1> = -1 and <data2> being the
+   initial state of the CS# pin or -1 if the chip select pin is not supplied.
 
 Examples:
  ['CS-CHANGE', 1, 0]
@@ -116,12 +118,13 @@ class Decoder(srd.Decoder):
         self.misodata = self.mosidata = 0
         self.misobits = []
         self.mosibits = []
-        self.startsample = -1
+        self.ss_block = -1
         self.samplenum = -1
         self.cs_was_deasserted = False
         self.oldcs = -1
         self.oldpins = None
         self.have_cs = self.have_miso = self.have_mosi = None
+        self.no_cs_notification = False
 
     def metadata(self, key, value):
         if key == srd.SRD_CONF_SAMPLERATE:
@@ -134,7 +137,7 @@ class Decoder(srd.Decoder):
                 meta=(int, 'Bitrate', 'Bitrate during transfers'))
 
     def putw(self, data):
-        self.put(self.startsample, self.samplenum, self.out_ann, data)
+        self.put(self.ss_block, self.samplenum, self.out_ann, data)
 
     def putdata(self):
         # Pass MISO and MOSI bits and then data to the next PD up the stack.
@@ -175,7 +178,7 @@ class Decoder(srd.Decoder):
     def handle_bit(self, miso, mosi, clk, cs):
         # If this is the first bit of a dataword, save its sample number.
         if self.bitcount == 0:
-            self.startsample = self.samplenum
+            self.ss_block = self.samplenum
             self.cs_was_deasserted = False
             if self.have_cs:
                 active_low = (self.options['cs_polarity'] == 'active-low')
@@ -225,9 +228,9 @@ class Decoder(srd.Decoder):
 
         # Meta bitrate.
         elapsed = 1 / float(self.samplerate)
-        elapsed *= (self.samplenum - self.startsample + 1)
+        elapsed *= (self.samplenum - self.ss_block + 1)
         bitrate = int(1 / elapsed * self.options['wordsize'])
-        self.put(self.startsample, self.samplenum, self.out_bitrate, bitrate)
+        self.put(self.ss_block, self.samplenum, self.out_bitrate, bitrate)
 
         if self.have_cs and self.cs_was_deasserted:
             self.putw([4, ['CS# was deasserted during this data word!']])
@@ -281,4 +284,9 @@ class Decoder(srd.Decoder):
             if not (self.have_miso or self.have_mosi):
                 raise ChannelError('Either MISO or MOSI (or both) pins required.')
 
+            # Tell stacked decoders that we don't have a CS# signal.
+            if not self.no_cs_notification and not self.have_cs:
+                self.put(0, 0, self.out_python, ['CS-CHANGE', -1, -1])
+                self.no_cs_notification = True
+
             self.find_clk_edge(miso, mosi, clk, cs)