About

Receive monitoring data from a squeow AM transmitter.

read.py will (using decoder.py) connect to a serial port, print values to stdout, and send values to a webserver

webserver.py is such a webserver. It provides an authenticated API for receiving values (most likely by read.py) and an unauthenticated API to get values.

Howto

Dependencies

apt install python3-fastapi python3-serial python3-requests

Run

./read.py -v --baudrate 115200 --wait --device /dev/pts/17 --http-endpoint http://127.0.0.1:8000 --http-auth-file password.txt

uvicorn webserver:app

Serial protocol

Goals

receive-only

if you only want to receive data, you shouldn't need to ask for data. This makes it possible to connect a serial port to multiple receivers!

machine and human-readable

this software will parse messages, but even if you don't have it around, you should be able to read messages just opening minicom.

High level description

Messages are started by the 0x01 ascii character (SOH start of heading) and ended by 0x0A ("\n", NL, new line). A messages needs to be entirely ascii.

There are two types of messages:

• log messages
• dump messages

Dump messages

Example: DMP freq=1234567 temp1=78 temp2=50 alm_temp=0 ros=4095 alm_ros=1

DMP is just a prefix to indicate the kind of message. Follows a space-separated sequence of key-values. A value is any string (including numbers, but no spaces). Please only use lowercase letters, numbers, and underscore ([a-z0-9_]). Values can only be integral positive numbers. Booleans don't have any specific form of support.

It is allowed to send dump messages which only inform the receiver about a part of the state, and not all of it. It's the receiver's responsibility to keep track of the whole state, and updating it whenever a new dump message arrives.

Log messages

Examples :

LOG I starting
LOG E overcurrent protection

LOG is just a prefix. Then a space Then a single capital letter indicating the severity of the message. Then a space. Whatever follows is the actual message

This makes it possible for debug messages to be sent.

Monitoring

None of the software provided will include monitoring functionalities. However, it will be easy to integrate with an existing monitoring service:

Nagios

This check will verify whether the alarm for temp1 is off

/usr/lib/nagios/plugins/check_http --regex '^0$' -I 127.0.0.1 -p 8000 --url=/variables/alm_temp1

If you want to check whether the squeow microcontroller is still alive, this will check that the last message was received from the microcontroller less than 100s ago.

/usr/lib/nagios/plugins/check_http --regex '^squeow_time_since_last_seen [0-9][0-9]?$' -I 127.0.0.1 -p 8000 --url=/metrics

Prometheus

a /metrics endpoint is exposed with the common metric=value format, which is easily to integrate into your prometheus instance.

Adding something like this at the end of the scrape_configs section of your prometheus.yml could be enough:

- job_name: 'squeow'

  # Override the global default and scrape targets from this job every 5 seconds.
  scrape_interval: 5s
  scrape_timeout: 5s

  # metrics_path defaults to '/metrics'
  # scheme defaults to 'http'.

  static_configs:
    - targets: ['localhost:8000']

Development

Simulate a serial port

you might want to avoid developing with the squeow microcontroller actually connected to your computer, and just simulate it.

if you want to do so, run:

socat -d -d pty,raw,echo=0 pty,raw,echo=0

Now, read the output; the first two lines would be sth like

2013/11/01 13:47:27 socat[2506] N PTY is /dev/pts/2
2013/11/01 13:47:27 socat[2506] N PTY is /dev/pts/3

This means that your read.py must use --device /dev/pts/2.

To simulate the reception of a message from the microcontroller, do this

echo -e '\x01DMP freq=1234567 temp1=78 temp2=50 alm_temp=0 ros=4095 alm_ros=1' > /dev/pts/3