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HWP Encoder BBB Agent

The optical encoder signals of the CHWP are captured by Beaglebone Black (BBB) boards with the IRIG-B timing reference. This agent receives and decodes UDP packets from BBB and publishes the data feeds.

Configuration File Examples

Below are useful configurations examples for the relevant OCS files and for running the agent in a docker container.

OCS Site Config

To configure the CHWP encoder BBB agent we need to add a HWPBBBAgent block to our ocs configuration file. Here is an example configuration block using all of the available arguments:

{'agent-class': 'HWPBBBAgent',
 'instance-id': 'HBA0',
 'arguments': [
   ['--port', '8080'],
   ]}
{'agent-class': 'HWPBBBAgent',
 'instance-id': 'HBA1',
 'arguments': [
   ['--port', '8081'],
   ]}

This is an example to run two agents because we usually have a couple of BBBs for A and B phase of the optical encoder for some redundancy. Multiple BBBs on the same network are distinguished by port numbers. You should assign a port for each BBB, which should be consistent with the setting on the BBB side.

Docker Compose

The CHWP BBB agent can be run via a Docker container. The following is an example of what to insert into your institution's docker-compose file. This again is an example to run multiple agents:

ocs-hwpbbb-agent-HBA0:
  image: simonsobs/socs:latest
  ports:
    - "8080:8080/udp"
  hostname: ocs-docker
  environment:
    - INSTANCE_ID=HBA0
  volumes:
    - ${OCS_CONFIG_DIR}:/config:ro

ocs-hwpbbb-agent-HBA1:
  image: simonsobs/socs:latest
  ports:
    - "8081:8081/udp"
  hostname: ocs-docker
  environment:
    - INSTANCE_ID=HBA1
  volumes:
    - ${OCS_CONFIG_DIR}:/config:ro

Description

session.data

The most recent data collected is stored in session.data in the following structure. The approx_hwp_freq is initialized by -1 and will be updated by non-negative rotation frequency if encoder agent is receiving encoder signal. If chwp is completely stopped, approx_hwp_freq will not be updated.:

>>> response.session['data']
{'approx_hwp_freq':      2.0,
 'encoder_last_updated': 1659486962.3731978,
 'irig_time':            1659486983,
 'irig_last_updated':    1659486983.8985631}

Agent API

socs.agents.hwp_encoder.agent.HWPBBBAgent