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Relax BitTiming & BitTimingFd Validation (#1618)
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* add `strict` parameter to can.BitTiming

* add `strict` parameter to can.BitTimingFd

* use `strict` in `from_bitrate_and_segments` and `recreate_with_f_clock`

* cover `strict` parameter in tests

* pylint: disable=too-many-arguments
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@zariiii9003
zariiii9003 authored Sep 17, 2023
1 parent e09d35e commit db177b3
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Showing 4 changed files with 181 additions and 70 deletions.
160 changes: 105 additions & 55 deletions can/bit_timing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ def __init__(
tseg2: int,
sjw: int,
nof_samples: int = 1,
strict: bool = False,
) -> None:
"""
:param int f_clock:
Expand All @@ -56,6 +57,10 @@ def __init__(
In this case, the bit will be sampled three quanta in a row,
with the last sample being taken in the edge between TSEG1 and TSEG2.
Three samples should only be used for relatively slow baudrates.
:param bool strict:
If True, restrict bit timings to the minimum required range as defined in
ISO 11898. This can be used to ensure compatibility across a wide variety
of CAN hardware.
:raises ValueError:
if the arguments are invalid.
"""
Expand All @@ -68,19 +73,13 @@ def __init__(
"nof_samples": nof_samples,
}
self._validate()
if strict:
self._restrict_to_minimum_range()

def _validate(self) -> None:
if not 8 <= self.nbt <= 25:
raise ValueError(f"nominal bit time (={self.nbt}) must be in [8...25].")

if not 1 <= self.brp <= 64:
raise ValueError(f"bitrate prescaler (={self.brp}) must be in [1...64].")

if not 5_000 <= self.bitrate <= 2_000_000:
raise ValueError(
f"bitrate (={self.bitrate}) must be in [5,000...2,000,000]."
)

if not 1 <= self.tseg1 <= 16:
raise ValueError(f"tseg1 (={self.tseg1}) must be in [1...16].")

Expand All @@ -104,6 +103,18 @@ def _validate(self) -> None:
if self.nof_samples not in (1, 3):
raise ValueError("nof_samples must be 1 or 3")

def _restrict_to_minimum_range(self) -> None:
if not 8 <= self.nbt <= 25:
raise ValueError(f"nominal bit time (={self.nbt}) must be in [8...25].")

if not 1 <= self.brp <= 32:
raise ValueError(f"bitrate prescaler (={self.brp}) must be in [1...32].")

if not 5_000 <= self.bitrate <= 1_000_000:
raise ValueError(
f"bitrate (={self.bitrate}) must be in [5,000...1,000,000]."
)

@classmethod
def from_bitrate_and_segments(
cls,
Expand All @@ -113,6 +124,7 @@ def from_bitrate_and_segments(
tseg2: int,
sjw: int,
nof_samples: int = 1,
strict: bool = False,
) -> "BitTiming":
"""Create a :class:`~can.BitTiming` instance from bitrate and segment lengths.
Expand All @@ -134,6 +146,10 @@ def from_bitrate_and_segments(
In this case, the bit will be sampled three quanta in a row,
with the last sample being taken in the edge between TSEG1 and TSEG2.
Three samples should only be used for relatively slow baudrates.
:param bool strict:
If True, restrict bit timings to the minimum required range as defined in
ISO 11898. This can be used to ensure compatibility across a wide variety
of CAN hardware.
:raises ValueError:
if the arguments are invalid.
"""
Expand All @@ -149,6 +165,7 @@ def from_bitrate_and_segments(
tseg2=tseg2,
sjw=sjw,
nof_samples=nof_samples,
strict=strict,
)
if abs(bt.bitrate - bitrate) > bitrate / 256:
raise ValueError(
Expand All @@ -175,6 +192,11 @@ def from_registers(
:raises ValueError:
if the arguments are invalid.
"""
if not 0 <= btr0 < 2**16:
raise ValueError(f"Invalid btr0 value. ({btr0})")
if not 0 <= btr1 < 2**16:
raise ValueError(f"Invalid btr1 value. ({btr1})")

brp = (btr0 & 0x3F) + 1
sjw = (btr0 >> 6) + 1
tseg1 = (btr1 & 0xF) + 1
Expand Down Expand Up @@ -239,6 +261,7 @@ def from_sample_point(
tseg1=tseg1,
tseg2=tseg2,
sjw=sjw,
strict=True,
)
possible_solutions.append(bt)
except ValueError:
Expand Down Expand Up @@ -316,12 +339,12 @@ def sample_point(self) -> float:

@property
def btr0(self) -> int:
"""Bit timing register 0."""
"""Bit timing register 0 for SJA1000."""
return (self.sjw - 1) << 6 | self.brp - 1

@property
def btr1(self) -> int:
"""Bit timing register 1."""
"""Bit timing register 1 for SJA1000."""
sam = 1 if self.nof_samples == 3 else 0
return sam << 7 | (self.tseg2 - 1) << 4 | self.tseg1 - 1

Expand Down Expand Up @@ -373,6 +396,7 @@ def recreate_with_f_clock(self, f_clock: int) -> "BitTiming":
tseg2=self.tseg2,
sjw=self.sjw,
nof_samples=self.nof_samples,
strict=True,
)
except ValueError:
pass
Expand Down Expand Up @@ -474,7 +498,7 @@ class BitTimingFd(Mapping):
)
"""

def __init__(
def __init__( # pylint: disable=too-many-arguments
self,
f_clock: int,
nom_brp: int,
Expand All @@ -485,6 +509,7 @@ def __init__(
data_tseg1: int,
data_tseg2: int,
data_sjw: int,
strict: bool = False,
) -> None:
"""
Initialize a BitTimingFd instance with the specified parameters.
Expand Down Expand Up @@ -513,6 +538,10 @@ def __init__(
:param int data_sjw:
The Synchronization Jump Width for the data phase. This value determines
the maximum number of time quanta that the controller can resynchronize every bit.
:param bool strict:
If True, restrict bit timings to the minimum required range as defined in
ISO 11898. This can be used to ensure compatibility across a wide variety
of CAN hardware.
:raises ValueError:
if the arguments are invalid.
"""
Expand All @@ -528,32 +557,23 @@ def __init__(
"data_sjw": data_sjw,
}
self._validate()
if strict:
self._restrict_to_minimum_range()

def _validate(self) -> None:
if self.nbt < 8:
raise ValueError(f"nominal bit time (={self.nbt}) must be at least 8.")

if self.dbt < 8:
raise ValueError(f"data bit time (={self.dbt}) must be at least 8.")

if not 1 <= self.nom_brp <= 256:
raise ValueError(
f"nominal bitrate prescaler (={self.nom_brp}) must be in [1...256]."
)

if not 1 <= self.data_brp <= 256:
raise ValueError(
f"data bitrate prescaler (={self.data_brp}) must be in [1...256]."
)
for param, value in self._data.items():
if value < 0: # type: ignore[operator]
err_msg = f"'{param}' (={value}) must not be negative."
raise ValueError(err_msg)

if not 5_000 <= self.nom_bitrate <= 2_000_000:
if self.nom_brp < 1:
raise ValueError(
f"nom_bitrate (={self.nom_bitrate}) must be in [5,000...2,000,000]."
f"nominal bitrate prescaler (={self.nom_brp}) must be at least 1."
)

if not 25_000 <= self.data_bitrate <= 8_000_000:
if self.data_brp < 1:
raise ValueError(
f"data_bitrate (={self.data_bitrate}) must be in [25,000...8,000,000]."
f"data bitrate prescaler (={self.data_brp}) must be at least 1."
)

if self.data_bitrate < self.nom_bitrate:
Expand All @@ -562,30 +582,12 @@ def _validate(self) -> None:
f"equal to nom_bitrate (={self.nom_bitrate})"
)

if not 2 <= self.nom_tseg1 <= 256:
raise ValueError(f"nom_tseg1 (={self.nom_tseg1}) must be in [2...256].")

if not 1 <= self.nom_tseg2 <= 128:
raise ValueError(f"nom_tseg2 (={self.nom_tseg2}) must be in [1...128].")

if not 1 <= self.data_tseg1 <= 32:
raise ValueError(f"data_tseg1 (={self.data_tseg1}) must be in [1...32].")

if not 1 <= self.data_tseg2 <= 16:
raise ValueError(f"data_tseg2 (={self.data_tseg2}) must be in [1...16].")

if not 1 <= self.nom_sjw <= 128:
raise ValueError(f"nom_sjw (={self.nom_sjw}) must be in [1...128].")

if self.nom_sjw > self.nom_tseg2:
raise ValueError(
f"nom_sjw (={self.nom_sjw}) must not be "
f"greater than nom_tseg2 (={self.nom_tseg2})."
)

if not 1 <= self.data_sjw <= 16:
raise ValueError(f"data_sjw (={self.data_sjw}) must be in [1...128].")

if self.data_sjw > self.data_tseg2:
raise ValueError(
f"data_sjw (={self.data_sjw}) must not be "
Expand All @@ -604,8 +606,46 @@ def _validate(self) -> None:
f"(data_sample_point={self.data_sample_point:.2f}%)."
)

def _restrict_to_minimum_range(self) -> None:
# restrict to minimum required range as defined in ISO 11898
if not 8 <= self.nbt <= 80:
raise ValueError(f"Nominal bit time (={self.nbt}) must be in [8...80]")

if not 5 <= self.dbt <= 25:
raise ValueError(f"Nominal bit time (={self.dbt}) must be in [5...25]")

if not 1 <= self.data_tseg1 <= 16:
raise ValueError(f"data_tseg1 (={self.data_tseg1}) must be in [1...16].")

if not 2 <= self.data_tseg2 <= 8:
raise ValueError(f"data_tseg2 (={self.data_tseg2}) must be in [2...8].")

if not 1 <= self.data_sjw <= 8:
raise ValueError(f"data_sjw (={self.data_sjw}) must be in [1...8].")

if self.nom_brp == self.data_brp:
# shared prescaler
if not 2 <= self.nom_tseg1 <= 128:
raise ValueError(f"nom_tseg1 (={self.nom_tseg1}) must be in [2...128].")

if not 2 <= self.nom_tseg2 <= 32:
raise ValueError(f"nom_tseg2 (={self.nom_tseg2}) must be in [2...32].")

if not 1 <= self.nom_sjw <= 32:
raise ValueError(f"nom_sjw (={self.nom_sjw}) must be in [1...32].")
else:
# separate prescaler
if not 2 <= self.nom_tseg1 <= 64:
raise ValueError(f"nom_tseg1 (={self.nom_tseg1}) must be in [2...64].")

if not 2 <= self.nom_tseg2 <= 16:
raise ValueError(f"nom_tseg2 (={self.nom_tseg2}) must be in [2...16].")

if not 1 <= self.nom_sjw <= 16:
raise ValueError(f"nom_sjw (={self.nom_sjw}) must be in [1...16].")

@classmethod
def from_bitrate_and_segments(
def from_bitrate_and_segments( # pylint: disable=too-many-arguments
cls,
f_clock: int,
nom_bitrate: int,
Expand All @@ -616,6 +656,7 @@ def from_bitrate_and_segments(
data_tseg1: int,
data_tseg2: int,
data_sjw: int,
strict: bool = False,
) -> "BitTimingFd":
"""
Create a :class:`~can.BitTimingFd` instance with the bitrates and segments lengths.
Expand Down Expand Up @@ -644,6 +685,10 @@ def from_bitrate_and_segments(
:param int data_sjw:
The Synchronization Jump Width for the data phase. This value determines
the maximum number of time quanta that the controller can resynchronize every bit.
:param bool strict:
If True, restrict bit timings to the minimum required range as defined in
ISO 11898. This can be used to ensure compatibility across a wide variety
of CAN hardware.
:raises ValueError:
if the arguments are invalid.
"""
Expand All @@ -665,6 +710,7 @@ def from_bitrate_and_segments(
data_tseg1=data_tseg1,
data_tseg2=data_tseg2,
data_sjw=data_sjw,
strict=strict,
)

if abs(bt.nom_bitrate - nom_bitrate) > nom_bitrate / 256:
Expand Down Expand Up @@ -724,34 +770,36 @@ def from_sample_point(

possible_solutions: List[BitTimingFd] = []

sync_seg = 1

for nom_brp in range(1, 257):
nbt = round(int(f_clock / (nom_bitrate * nom_brp)))
if nbt < 8:
if nbt < 1:
break

effective_nom_bitrate = f_clock / (nbt * nom_brp)
if abs(effective_nom_bitrate - nom_bitrate) > nom_bitrate / 256:
continue

nom_tseg1 = int(round(nom_sample_point / 100 * nbt)) - 1
# limit tseg1, so tseg2 is at least 1 TQ
nom_tseg1 = min(nom_tseg1, nbt - 2)
# limit tseg1, so tseg2 is at least 2 TQ
nom_tseg1 = min(nom_tseg1, nbt - sync_seg - 2)
nom_tseg2 = nbt - nom_tseg1 - 1

nom_sjw = min(nom_tseg2, 128)

for data_brp in range(1, 257):
dbt = round(int(f_clock / (data_bitrate * data_brp)))
if dbt < 8:
if dbt < 1:
break

effective_data_bitrate = f_clock / (dbt * data_brp)
if abs(effective_data_bitrate - data_bitrate) > data_bitrate / 256:
continue

data_tseg1 = int(round(data_sample_point / 100 * dbt)) - 1
# limit tseg1, so tseg2 is at least 1 TQ
data_tseg1 = min(data_tseg1, dbt - 2)
# limit tseg1, so tseg2 is at least 2 TQ
data_tseg1 = min(data_tseg1, dbt - sync_seg - 2)
data_tseg2 = dbt - data_tseg1 - 1

data_sjw = min(data_tseg2, 16)
Expand All @@ -767,6 +815,7 @@ def from_sample_point(
data_tseg1=data_tseg1,
data_tseg2=data_tseg2,
data_sjw=data_sjw,
strict=True,
)
possible_solutions.append(bt)
except ValueError:
Expand Down Expand Up @@ -971,6 +1020,7 @@ def recreate_with_f_clock(self, f_clock: int) -> "BitTimingFd":
data_tseg1=self.data_tseg1,
data_tseg2=self.data_tseg2,
data_sjw=self.data_sjw,
strict=True,
)
except ValueError:
pass
Expand Down
6 changes: 4 additions & 2 deletions can/util.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -250,14 +250,16 @@ def _create_bus_config(config: Dict[str, Any]) -> typechecking.BusConfig:
**{
key: int(config[key])
for key in typechecking.BitTimingFdDict.__annotations__
}
},
strict=False,
)
elif set(typechecking.BitTimingDict.__annotations__).issubset(config):
config["timing"] = can.BitTiming(
**{
key: int(config[key])
for key in typechecking.BitTimingDict.__annotations__
}
},
strict=False,
)
except (ValueError, TypeError):
pass
Expand Down
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