## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
-## along with this program; if not, write to the Free Software
-## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+## along with this program; if not, see <http://www.gnu.org/licenses/>.
##
import sigrokdecode as srd
+class SamplerateError(Exception):
+ pass
+
class Decoder(srd.Decoder):
- api_version = 1
+ api_version = 3
id = 'can'
name = 'CAN'
longname = 'Controller Area Network'
license = 'gplv2+'
inputs = ['logic']
outputs = ['can']
- probes = (
+ channels = (
{'id': 'can_rx', 'name': 'CAN RX', 'desc': 'CAN bus line'},
)
options = (
('ack-delimiter', 'ACK delimiter'),
('stuff-bit', 'Stuff bit'),
('warnings', 'Human-readable warnings'),
+ ('bit', 'Bit'),
+ )
+ annotation_rows = (
+ ('bits', 'Bits', (15, 17)),
+ ('fields', 'Fields', tuple(range(15))),
+ ('warnings', 'Warnings', (16,)),
)
- def __init__(self, **kwargs):
+ def __init__(self):
+ self.reset()
+
+ def reset(self):
self.samplerate = None
self.reset_variables()
def start(self):
- # self.out_python = self.register(srd.OUTPUT_PYTHON)
self.out_ann = self.register(srd.OUTPUT_ANN)
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
self.bit_width = float(self.samplerate) / float(self.options['bitrate'])
- self.bitpos = (self.bit_width / 100.0) * self.options['sample_point']
+ self.sample_point = (self.bit_width / 100.0) * self.options['sample_point']
# Generic helper for CAN bit annotations.
def putg(self, ss, es, data):
- left, right = int(self.bitpos), int(self.bit_width - self.bitpos)
+ left, right = int(self.sample_point), int(self.bit_width - self.sample_point)
self.put(ss - left, es + right, self.out_ann, data)
# Single-CAN-bit annotation using the current samplenum.
self.ss_bit12 = None
self.ss_databytebits = []
- # Return True if we reached the desired bit position, False otherwise.
- def reached_bit(self, bitnum):
- bitpos = int(self.sof + (self.bit_width * bitnum) + self.bitpos)
- if self.samplenum >= bitpos:
- return True
- return False
+ # Poor man's clock synchronization. Use signal edges which change to
+ # dominant state in rather simple ways. This naive approach is neither
+ # aware of the SYNC phase's width nor the specific location of the edge,
+ # but improves the decoder's reliability when the input signal's bitrate
+ # does not exactly match the nominal rate.
+ def dom_edge_seen(self, force = False):
+ self.dom_edge_snum = self.samplenum
+ self.dom_edge_bcount = self.curbit
+
+ def bit_sampled(self):
+ # EMPTY
+ pass
+
+ # Determine the position of the next desired bit's sample point.
+ def get_sample_point(self, bitnum):
+ samplenum = self.dom_edge_snum
+ samplenum += int(self.bit_width * (bitnum - self.dom_edge_bcount))
+ samplenum += int(self.sample_point)
+ return samplenum
def is_stuff_bit(self):
# CAN uses NRZ encoding and bit stuffing.
# After 5 identical bits, a stuff bit of opposite value is added.
+ # But not in the CRC delimiter, ACK, and end of frame fields.
+ if len(self.bits) > self.last_databit + 17:
+ return False
last_6_bits = self.rawbits[-6:]
if last_6_bits not in ([0, 0, 0, 0, 0, 1], [1, 1, 1, 1, 1, 0]):
return False
# Stuff bit. Keep it in self.rawbits, but drop it from self.bits.
- self.putx([15, ['Stuff bit: %d' % self.rawbits[-1],
- 'SB: %d' % self.rawbits[-1], 'SB']])
self.bits.pop() # Drop last bit.
return True
elif bitnum == (self.last_databit + 16):
self.putx([12, ['CRC delimiter: %d' % can_rx,
'CRC d: %d' % can_rx, 'CRC d']])
+ if can_rx != 1:
+ self.putx([16, ['CRC delimiter must be a recessive bit']])
# ACK slot bit (dominant: ACK, recessive: NACK)
elif bitnum == (self.last_databit + 17):
elif bitnum == (self.last_databit + 18):
self.putx([14, ['ACK delimiter: %d' % can_rx,
'ACK d: %d' % can_rx, 'ACK d']])
+ if can_rx != 1:
+ self.putx([16, ['ACK delimiter must be a recessive bit']])
# Remember start of EOF (see below).
elif bitnum == (self.last_databit + 19):
# End of frame (EOF), 7 recessive bits
elif bitnum == (self.last_databit + 25):
self.putb([2, ['End of frame', 'EOF', 'E']])
+ if self.rawbits[-7:] != [1, 1, 1, 1, 1, 1, 1]:
+ self.putb([16, ['End of frame (EOF) must be 7 recessive bits']])
self.reset_variables()
return True
self.putb([10, ['Data length code: %d' % self.dlc,
'DLC: %d' % self.dlc, 'DLC']])
self.last_databit = 18 + (self.dlc * 8)
+ if self.dlc > 8:
+ self.putb([16, ['Data length code (DLC) > 8 is not allowed']])
# Remember all databyte bits, except the very last one.
elif bitnum in range(19, self.last_databit):
# Get the index of the current CAN frame bit (without stuff bits).
bitnum = len(self.bits) - 1
- # For debugging.
- # self.putx([0, ['Bit %d (CAN bit %d): %d' % \
- # (self.curbit, bitnum, can_rx)]])
-
# If this is a stuff bit, remove it from self.bits and ignore it.
if self.is_stuff_bit():
+ self.putx([15, [str(can_rx)]])
self.curbit += 1 # Increase self.curbit (bitnum is not affected).
return
+ else:
+ self.putx([17, [str(can_rx)]])
# Bit 0: Start of frame (SOF) bit
if bitnum == 0:
- if can_rx == 0:
- self.putx([1, ['Start of frame', 'SOF', 'S']])
- else:
+ self.putx([1, ['Start of frame', 'SOF', 'S']])
+ if can_rx != 0:
self.putx([16, ['Start of frame (SOF) must be a dominant bit']])
# Remember start of ID (see below).
self.id = int(''.join(str(d) for d in self.bits[1:]), 2)
s = '%d (0x%x)' % (self.id, self.id),
self.putb([3, ['Identifier: %s' % s, 'ID: %s' % s, 'ID']])
+ if (self.id & 0x7f0) == 0x7f0:
+ self.putb([16, ['Identifier bits 10..4 must not be all recessive']])
# RTR or SRR bit, depending on frame type (gets handled later).
elif bitnum == 12:
self.curbit += 1
- def decode(self, ss, es, data):
- if self.samplerate is None:
- raise Exception("Cannot decode without samplerate.")
- for (self.samplenum, pins) in data:
-
- (can_rx,) = pins
+ def decode(self):
+ if not self.samplerate:
+ raise SamplerateError('Cannot decode without samplerate.')
+ while True:
# State machine.
if self.state == 'IDLE':
# Wait for a dominant state (logic 0) on the bus.
- if can_rx == 1:
- continue
+ (can_rx,) = self.wait({0: 'l'})
self.sof = self.samplenum
+ self.dom_edge_seen(force = True)
self.state = 'GET BITS'
elif self.state == 'GET BITS':
# Wait until we're in the correct bit/sampling position.
- if not self.reached_bit(self.curbit):
- continue
- self.handle_bit(can_rx)
- else:
- raise Exception("Invalid state: %s" % self.state)
-
+ pos = self.get_sample_point(self.curbit)
+ (can_rx,) = self.wait([{'skip': pos - self.samplenum}, {0: 'f'}])
+ if self.matched[1]:
+ self.dom_edge_seen()
+ if self.matched[0]:
+ self.handle_bit(can_rx)
+ self.bit_sampled()
projects / libsigrokdecode.git / blobdiff