cmd/

Go CLI Programs

iotcorelogger and readtemp contain code that runs on the Raspberry Pi. iotcorelogger reads the temperature and logs it via AWS IoT Core, storing the data in Google Cloud Datastore (see the Docker image in the web directory).

From the root of this repository,

make

# Example device.json:
# {
#   "endpoint": "endpoint-name",
#   "device_id": "my-device",
#   "cert_path": "my-device.x509",
#   "priv_key_path": "my-device.pem"
# }
./out/iotcorelogger -aws-device device.json

# Print temp to stdout
./out/readtemp

Prerequisites

On your development machine / where you'll build (No, you do not need to build on the Raspberry Pi! In fact it is slow and painful to do so.):

1. Don't have Go installed? It's super easy.
2. You'll need the protocol buffer compiler, version 3.0.0 or higher. Follow the instructions here — all you have to do is download a pre-built release for your platform and make sure the compiler, protoc, is on your PATH.
3. You'll also need the protobuf compiler plugin that generates Go code. Follow the instructions here, or TL;DR: go get -u github.com/golang/protobuf/protoc-gen-go

Building

From the root of this repository,

make

Simple as that. This will build the iotcorelogger program for the host architecture as well as ARMv6 (e.g. Raspberry Pi Zero W) and ARMv7 (e.g. Raspberry Pi 3 B¹).

Full usage

usage: iotcorelogger [options]

Options:
  -aws-device string
      path to a device config file describing an AWS IoT Core device
  -dryrun
      set to true to print rather than publish measurements
  -port int
      port on which the device's web server should listen (default 8080)

iotcorelogger sensor and job configuration

The iotcorelogger program is told which sensors to use and the frequency at which to take measurements via a JSON job spec. A job has:

• A cronspec
• An operation, which must be one of "SETUP", "SENSE", or "SHUTDOWN"
• A list of sensors

Example of a simple config that gets a measurement from an MCP9808 temperature sensor every 2 minutes:

{
  "jobs": [
    {
      "cronspec": "0 */2 * * * *",
      "operation": "SENSE",
      "sensors": ["mcp9808"]
    }
  ]
}

Example of a more complex config that gets particulate matter measurements from an SDS011 sensor every 2 minutes, but that runs setup and shutdown jobs before taking measurements.

{
  "jobs": [
    {
      "cronspec": "35 1-59/2 * * * *",
      "operation": "SETUP",
      "sensors": [
        "sds011"
      ]
    },
    {
      "cronspec": "0 0-59/2 * * * *",
      "operation": "SENSE",
      "sensors": [
        "sds011"
      ]
    },
    {
      "cronspec": "8 0-59/2 * * * *",
      "operation": "SHUTDOWN",
      "sensors": [
        "sds011"
      ]
    }
  ]
}

The device receives this config from an AWS IoT Core Device Shadow. See Device Shadow service documentation here.

When a device connects to the MQTT broker it will either create a shadow if one doesn't exist, or fetch the current desired config from the shadow. Set the desired config in the device's shadow configuration to push it to the device; the device will receive and apply the new config any time it is changed.

Footnotes

¹ "How can this be!? The Raspberry Pi 3 B uses the BCM2837, a 64-bit ARMv8 SoC!" you exclaim. "That is correct," I reply, "but Raspbian is 32-bit only so the chip runs in 32-bit mode. It therefore cannot execute ARMv8 binaries."