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Auto Control

Finally, we will use this virtual joystick and the canbus client / service connection to control the Amiga to complete the full Virtual Joystick example.

Control the Amiga

This is done with a third forever-running asyncio task for sending CAN messages.

This task waits for a RUNNING canbus client state, to ensure there is feedback on the measured speeds before sending any commands. This is a must for closed loop control!

Once the canbus client is in a full RUNNING state, the task initializes the Bidirectional streaming RPC called sendCanbusMessage.

This passes a Python Generator that constructs and yields a SendCanbusMessageRequest containing a RawCanbusMessage, both proto definitions from canbus.proto.

The RawCanbusMessage encodes an AmigaRpdo1 auto control request that is forward by the canbus service to the Amiga dashboard. This includes requested state, speed, and angular rate of the Amiga. As you can see, the requested speed and angular rate are based on the position of the VirtualJoystickWidget.

tip

The AmigaRpdo1 message is only a request. The vehicle control unit (VCU) in the Amiga dashboard has safety critical logic that prevents unsafe auto control.

Because this is a bi-directional stream, a response is returned for each RawCanbusMessage the generator yields. We can check the status of each of these responses, and exit the generator loop if the service does not respond with a confirmed success. Once the canbus service is ready for streaming control again, it should re-initiate automatically.

generator details

The pose generator yields an AmigaRpdo1 (auto control command) for the canbus client to send on the bus at the specified period (recommended 50hz) based on the on-screen joystick position.

Each loop of the generator we sleep to enforce the ideal rate of streaming AmigaRpdo1 CAN messages, which is 50 hz. You can modify the period parameter, but go too slow and you lose responsiveness, and go too fast and you risk saturating the CAN bus, which can cause loss of communication between all components on the bus.

Add this as a task

Remember to add the send_can_msgs() method to the asyncio. Task in our list in app_func()!

Run it

Now sync the app to the Brain and launch it.

caution

Make sure all your cables are disconnected from the Amiga and no one is in the way of the Amiga before driving around!

Everything should look just like the last checkpoint, but now you can drive the Amiga the the virtual joystick!

Navigate to the auto tab on the dashboard and enter the Auto Ready state. The Brain should take control and enter the Auto Active state right away, allowing you to drive with the screen. You should see the state on the dashboard match that displayed on the Brain in your app.

auto_control