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Vehicle Researcher
23bbf52578
286b7e58b capitalize docker command 0adfc7e77 add canErrorPersistent event c8be73d10 use github url instead of gitlab mirror 8e2d212a3 add pre-commit static analysis (#48) f27222f8f add gpsOK flag to liveLocationKalman 4bb1eb826 submaster always conflates 30838d40a C++ implementation of SubMaster and PubMaster (#42) c1a6d75d1 Fix potential segfault in MSGQPubSocket::connect (#45) 67fae6afc Use ZMQ on MacOS (#46) 01cdf832c add default values for backwards compat c96381b0d add OK flags to locationd output d589d5e3d add white panda deprecation events 856c9812d mark unused car events as deprecated 4f68db8f6 remove unnecessary new event type 9073b9b1b Library cleanup (#43) 7a786d9ce move remaining alerts to car events d6f10a4b9 add alert event type git-subtree-dir: cereal git-subtree-split: 286b7e58b5e7ede697370acc77fc7cca21d69764
What is cereal?
cereal is both a messaging spec for robotics systems as well as generic high performance IPC pub sub messaging with a single publisher and multiple subscribers.
Imagine this use case:
- A sensor process reads gyro measurements directly from an IMU and publishes a sensorEvents packet
- A calibration process subscribes to the sensorEvents packet to use the IMU
- A localization process subscribes to the sensorEvents packet to use the IMU also
Messaging Spec
You'll find the message types in log.capnp. It uses Cap'n proto and defines one struct called Event.
All Events have a logMonoTime and a valid. Then a big union defines the packet type.
Pub Sub Backends
cereal supports two backends, one based on zmq, the other called msgq, a custom pub sub based on shared memory that doesn't require the bytes to pass through the kernel.
Example
import cereal.messaging as messaging
# in subscriber
sm = messaging.SubMaster(['sensorEvents'])
while 1:
sm.update()
print(sm['sensorEvents'])
# in publisher
pm = messaging.PubMaster(['sensorEvents'])
dat = messaging.new_message('sensorEvents', size=1)
dat.sensorEvents[0] = {"gyro": {"v": [0.1, -0.1, 0.1]}}
pm.send('sensorEvents', dat)