usb_packet: Document CRC5 ERROR and CRC16 ERROR packets.

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

diff --git a/decoders/usb_packet/pd.py b/decoders/usb_packet/pd.py
index 740435665d3c907e5465f1cfbfce589f01888d90..7120d52932824d073269d0c58628fac64ce4bbca 100644 (file)
--- a/decoders/usb_packet/pd.py
+++ b/decoders/usb_packet/pd.py
@@ -33,7 +33,9 @@ Packet:
  - 'ADDR', <addr>
  - 'EP', <ep>
  - 'CRC5', <crc5>
+ - 'CRC5 ERROR', <crc5>
  - 'CRC16', <crc16>
+ - 'CRC16 ERROR', <crc16>
  - 'EOP', <eop>
  - 'FRAMENUM', <framenum>
  - 'DATABYTE', <databyte>
@@ -142,8 +144,37 @@ def bitstr_to_num(bitstr):
     l.reverse()
     return int(''.join(l), 2)
 
+def reverse_number(num, count):
+    out = list(count * '0')
+    for i in range(0, count):
+        if num >> i & 1:
+            out[i] = '1';
+    return int(''.join(out), 2)
+
+def calc_crc5(bitstr):
+    poly5 = 0x25
+    crc5 = 0x1f
+    for bit in bitstr:
+        crc5 <<= 1
+        if int(bit) != (crc5 >> 5):
+            crc5 ^= poly5
+        crc5 &= 0x1f
+    crc5 ^= 0x1f
+    return reverse_number(crc5, 5)
+
+def calc_crc16(bitstr):
+    poly16 = 0x18005
+    crc16 = 0xffff
+    for bit in bitstr:
+        crc16 <<= 1
+        if int(bit) != (crc16 >> 16):
+            crc16 ^= poly16
+        crc16 &= 0xffff
+    crc16 ^= 0xffff
+    return reverse_number(crc16, 16)
+
 class Decoder(srd.Decoder):
-    api_version = 1
+    api_version = 2
     id = 'usb_packet'
     name = 'USB packet'
     longname = 'Universal Serial Bus (LS/FS) packet'
@@ -187,12 +218,11 @@ class Decoder(srd.Decoder):
         ('packet-invalid', 'Packet: Invalid'),
     )
     annotation_rows = (
-        ('fields', 'Packet fields', tuple(range(11 + 1))),
-        ('packet', 'Packets', tuple(range(12, 28 + 1))),
+        ('fields', 'Packet fields', tuple(range(10 + 1))),
+        ('packet', 'Packets', tuple(range(11, 28 + 1))),
     )
 
     def __init__(self):
-        self.samplenum = 0
         self.bits = []
         self.packet = []
         self.packet_summary = ''
@@ -221,6 +251,10 @@ class Decoder(srd.Decoder):
         for (bit, ss, es) in self.bits:
             packet += bit
 
+        if len(packet) < 8:
+            self.putp([28, ['Invalid packet (shorter than 8 bits)']])
+            return
+
         # Bits[0:7]: SYNC
         sync = packet[:7 + 1]
         self.ss, self.es = self.bits[0][1], self.bits[7][2]
@@ -234,9 +268,13 @@ class Decoder(srd.Decoder):
             self.putb([0, ['SYNC: %s' % sync, 'SYNC', 'S']])
         self.packet.append(sync)
 
+        if len(packet) < 16:
+            self.putp([28, ['Invalid packet (shorter than 16 bits)']])
+            return
+
         # Bits[8:15]: PID
         pid = packet[8:15 + 1]
-        pidname = pids.get(pid, (pid, ''))[0]
+        pidname = pids.get(pid, ('UNKNOWN', 'Unknown PID'))[0]
         self.ss, self.es = self.bits[8][1], self.bits[15][2]
         self.putpb(['PID', pidname])
         self.putb([2, ['PID: %s' % pidname, pidname, pidname[0]]])
@@ -244,6 +282,10 @@ class Decoder(srd.Decoder):
         self.packet_summary += pidname
 
         if pidname in ('OUT', 'IN', 'SOF', 'SETUP', 'PRE', 'PING'):
+            if len(packet) < 32:
+                self.putp([28, ['Invalid packet (shorter than 32 bits)']])
+                return
+
             if pidname == 'SOF':
                 # Bits[16:26]: Framenum
                 framenum = bitstr_to_num(packet[16:26 + 1])
@@ -272,9 +314,14 @@ class Decoder(srd.Decoder):
 
             # Bits[27:31]: CRC5
             crc5 = bitstr_to_num(packet[27:31 + 1])
+            crc5_calc = calc_crc5(packet[16:27])
             self.ss, self.es = self.bits[27][1], self.bits[31][2]
-            self.putpb(['CRC5', crc5])
-            self.putb([6, ['CRC5: 0x%02X' % crc5, 'CRC5', 'C']])
+            if crc5 == crc5_calc:
+                self.putpb(['CRC5', crc5])
+                self.putb([6, ['CRC5: 0x%02X' % crc5, 'CRC5', 'C']])
+            else:
+                self.putpb(['CRC5 ERROR', crc5])
+                self.putb([7, ['CRC5 ERROR: 0x%02X' % crc5, 'CRC5 ERR', 'CE', 'C']])
             self.packet.append(crc5)
         elif pidname in ('DATA0', 'DATA1', 'DATA2', 'MDATA'):
             # Bits[16:packetlen-16]: Data
@@ -290,7 +337,6 @@ class Decoder(srd.Decoder):
                                'DB: %02X' % db, '%02X' % db]])
                 databytes.append(db)
                 self.packet_summary += ' %02X' % db
-                data = data[8:]
             self.packet_summary += ' ]'
 
             # Convenience Python output (no annotation) for all bytes together.
@@ -300,9 +346,14 @@ class Decoder(srd.Decoder):
 
             # Bits[packetlen-16:packetlen]: CRC16
             crc16 = bitstr_to_num(packet[-16:])
+            crc16_calc = calc_crc16(packet[16:-16])
             self.ss, self.es = self.bits[-16][1], self.bits[-1][2]
-            self.putpb(['CRC16', crc16])
-            self.putb([9, ['CRC16: 0x%04X' % crc16, 'CRC16', 'C']])
+            if crc16 == crc16_calc:
+                self.putpb(['CRC16', crc16])
+                self.putb([9, ['CRC16: 0x%04X' % crc16, 'CRC16', 'C']])
+            else:
+                self.putpb(['CRC16 ERROR', crc16])
+                self.putb([10, ['CRC16 ERROR: 0x%04X' % crc16, 'CRC16 ERR', 'CE', 'C']])
             self.packet.append(crc16)
         elif pidname in ('ACK', 'NAK', 'STALL', 'NYET', 'ERR'):
             pass # Nothing to do, these only have SYNC+PID+EOP fields.
@@ -335,9 +386,7 @@ class Decoder(srd.Decoder):
             elif ptype == 'EOP':
                 self.es_packet = es
                 self.handle_packet()
+                self.packet, self.packet_summary = [], ''
                 self.bits, self.state = [], 'WAIT FOR SOP'
             else:
                 pass # TODO: Error
-        else:
-            raise Exception('Invalid state: %s' % self.state)
-