srd: usb: Add long description of the PIDs.

[libsigrokdecode.git] / decoders / usb / usb.py

diff --git a/decoders/usb/usb.py b/decoders/usb/usb.py
index 15b42a9ee5360e4b11763d2e27e3522a409f830d..529868e2121ea6cb86ff07ccc1fcd992f0136723 100644 (file)
--- a/decoders/usb/usb.py
+++ b/decoders/usb/usb.py
@@ -18,33 +18,67 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 ##
 
-# USB (full-speed) protocol decoder
+# USB (low-speed and full-speed) protocol decoder
 
 import sigrokdecode as srd
 
-# Symbols (used as states of our state machine, too)
+# Full-speed symbols (used as states of our state machine, too).
+# Note: Low-speed J and K are inverted compared to the full-speed J and K!
 syms = {
-        # (<dp>, <dm>): <state>
+        # (<dp>, <dm>): <symbol/state>
         (0, 0): 'SE0',
         (1, 0): 'J',
         (0, 1): 'K',
         (1, 1): 'SE1',
 }
 
-# ...
+# Packet IDs (PIDs).
+# The first 4 bits are the 'packet type' field, the last 4 bits are the
+# 'check field' (each bit in the check field must be the inverse of the resp.
+# bit in the 'packet type' field; if not, that's a 'PID error').
+# For the 4-bit strings, the left-most '1' or '0' is the LSB, i.e. it's sent
+# to the bus first.
 pids = {
-    '10000111': 'OUT',      # Tokens
-    '10010110': 'IN',
-    '10100101': 'SOF',
-    '10110100': 'SETUP',
-    '11000011': 'DATA0',    # Data
-    '11010010': 'DATA1',
-    '01001011': 'ACK',      # Handshake
-    '01011010': 'NAK',
-    '01111000': 'STALL',
-    '01101001': 'NYET',
+    # Tokens
+    '10000111': ['OUT', 'Address & EP number in host-to-function transaction'],
+    '10010110': ['IN', 'Address & EP number in function-to-host transaction'],
+    '10100101': ['SOF', 'Start-Of-Frame marker & frame number'],
+    '10110100': ['SETUP', 'Address & EP number in host-to-function transaction for SETUP to a control pipe'],
+
+    # Data
+    # Note: DATA2 and MDATA are HS-only.
+    '11000011': ['DATA0', 'Data packet PID even'],
+    '11010010': ['DATA1', 'Data packet PID odd'],
+    '11100001': ['DATA2', 'Data packet PID HS, high bandwidth isosynchronous transaction in a microframe'],
+    '11110000': ['MDATA', 'Data packet PID HS for split and high-bandwidth isosynchronous transactions'],
+
+    # Handshake
+    '01001011': ['ACK', 'Receiver accepts error-free packet'],
+    '01011010': ['NAK', 'Receiver cannot accept or transmitter cannot send'],
+    '01111000': ['STALL', 'EP halted or control pipe request unsupported'],
+    '01101001': ['NYET', 'No response yet from receiver'],
+
+    # Special
+    '00111100': ['PRE', 'Host-issued preamble; enables downstream bus traffic to low-speed devices'],
+    '00111100': ['ERR', 'Split transaction error handshake'],
+    '00011110': ['SPLIT', 'HS split transaction token'],
+    '00101101': ['PING', 'HS flow control probe for a bulk/control EP'],
+    '00001111': ['Reserved', 'Reserved PID'],
 }
 
+def get_sym(signalling, dp, dm):
+    # Note: Low-speed J and K are inverted compared to the full-speed J and K!
+    if signalling == 'low-speed':
+        s = syms[dp, dm]
+        if s == 'J':
+            return 'K'
+        elif s == 'K':
+            return 'J'
+        else:
+            return s
+    elif signalling == 'full-speed':
+       return syms[dp, dm]
+
 def bitstr_to_num(bitstr):
     if not bitstr:
         return 0
@@ -55,7 +89,7 @@ def bitstr_to_num(bitstr):
 def packet_decode(packet):
     sync = packet[:8]
     pid = packet[8:16]
-    pid = pids.get(pid, pid)
+    pid = pids.get(pid, (pid, ''))[0]
 
     # Remove CRC.
     if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
@@ -76,6 +110,7 @@ def packet_decode(packet):
     else:
         data = packet[16:]
 
+    # The SYNC pattern for low-speed/full-speed is KJKJKJKK (0001).
     if sync != '00000001':
         return 'SYNC INVALID!'
 
@@ -85,8 +120,8 @@ class Decoder(srd.Decoder):
     api_version = 1
     id = 'usb'
     name = 'USB'
-    longname = 'Universal Serial Bus'
-    desc = 'USB 1.x (full-speed) serial protocol.'
+    longname = 'Universal Serial Bus (LS/FS)'
+    desc = 'USB 1.x (low-speed and full-speed) serial protocol.'
     license = 'gplv2+'
     inputs = ['logic']
     outputs = ['usb']
@@ -95,7 +130,9 @@ class Decoder(srd.Decoder):
         {'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
     ]
     optional_probes = []
-    options = {}
+    options = {
+        'signalling': ['Signalling', 'full-speed'],
+    }
     annotations = [
         ['Text', 'Human-readable text']
     ]
@@ -109,10 +146,6 @@ class Decoder(srd.Decoder):
     def start(self, metadata):
         self.samplerate = metadata['samplerate']
 
-        if self.samplerate < 48000000:
-            raise Exception('Samplerate (%d) not sufficient for USB '
-                            'decoding, need at least 48MHz' % self.samplerate)
-
         # self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
         self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
 
@@ -127,7 +160,7 @@ class Decoder(srd.Decoder):
             # last change in the D+/D- lines.
             self.scount += 1
 
-            sym = syms[dp, dm]
+            sym = get_sym(self.options['signalling'], dp, dm)
 
             # Wait for a symbol change (i.e., change in D+/D- lines).
             if sym == self.sym:
@@ -142,7 +175,11 @@ class Decoder(srd.Decoder):
 
             # How many bits since the last transition?
             if self.packet != '' or self.sym != 'J':
-                bitcount = int((self.scount - 1) * 12000000 / self.samplerate)
+                if self.options['signalling'] == 'low-speed':
+                    bitrate = 1500000 # 1.5Mb/s (+/- 1.5%)
+                elif self.options['signalling'] == 'full-speed':
+                    bitrate = 12000000 # 12Mb/s (+/- 0.25%)
+                bitcount = int((self.scount - 1) * bitrate / self.samplerate)
             else:
                 bitcount = 0