Parsing DSDL definitions

Create a file named namespace_a/Foo.uavcan with the following content:

uavcan.Timestamp timestamp
uint8 MY_FAVORITE_CHAR = '\x42'

Create another file named namespace_b/Bar.uavcan with the following content:

float16 x
float16[<8] y
---
uint6 JUST_ENOUGH = 42
float64 answer
namespace_a.Foo foo

Place the standard DSDL definitions into the directory dsdl/ (just clone or symlink the DSDL repository into the current directory).

The resulting directory structure should look like this:

namespace_a/
    Foo.uavcan
namespace_b/
    Bar.uavcan
dsdl/
    uavcan/
        ...
...

Put this code into a file in the current directory:

#
# PyDroneCAN DSDL parser demo.
# Read the package docstrings for details.
#

# pydronecan supports Python 2.7 and Python 3.x
from __future__ import print_function
from dronecan import dsdl

# Root namespace directories:
NAMESPACE_DIRS = ['namespace_a/', 'namespace_b/']

# Where to look for the referenced types (standard UAVCAN types):
SEARCH_DIRS = ['dsdl/uavcan']

# Run the DSDL parser:
types = dsdl.parse_namespaces(NAMESPACE_DIRS, SEARCH_DIRS)

# Print what we got
ATTRIBUTE_INDENT = ' ' * 3

def print_attributes(fields, constants):
    for a in fields:
        print(ATTRIBUTE_INDENT, a.type.full_name, a.name, end='  # ')
        # Add a bit of relevant information for this type:
        if a.type.category == a.type.CATEGORY_COMPOUND:
            print('DSDL signature: 0x%08X' % a.type.get_dsdl_signature())
        if a.type.category == a.type.CATEGORY_ARRAY:
            print('Max array size: %d' % a.type.max_size)
        if a.type.category == a.type.CATEGORY_PRIMITIVE:
            print('Bit length: %d' % a.type.bitlen)
    for a in constants:
        print(ATTRIBUTE_INDENT, a.type.full_name, a.name, '=', a.value, '#', a.init_expression)

for t in types:
    print(t.full_name)
    if t.kind == t.KIND_MESSAGE:
        print_attributes(t.fields, t.constants)
    elif t.kind == t.KIND_SERVICE:
        print_attributes(t.request_fields, t.request_constants)
        print(ATTRIBUTE_INDENT, '---')
        print_attributes(t.response_fields, t.response_constants)

Make sure the PyDroneCAN package is installed, then run the script. The output should look like this:

namespace_a.Foo
    uavcan.Timestamp timestamp  # DSDL signature: 0xF776DD8697A8DB73
    saturated uint8 MY_FAVORITE_CHAR = 66 # '\x42'
namespace_b.Bar
    saturated float16 x  # Bit length: 16
    saturated float16[<=7] y  # Max array size: 7
    ---
    saturated float64 answer  # Bit length: 64
    namespace_a.Foo foo  # DSDL signature: 0xFE327FCBE8C6F7D
    saturated uint6 JUST_ENOUGH = 42 # 42

For a real world usage example it’s recommended to refer to Libuavcan, which implements a DSDL compiler based on the DSDL parsing module from PyDroneCAN.

Parsing DSDL definitions

Pydronecan

License