# Overview

Performs sound level monitoring using a USB Benetech GM1356 sonometer.

Named after [Loud Howard](https://dilbert.com/strip/1995-04-21).

Big thanks to [Maciej Ciemborowicz](https://github.com/ciembor) for his work documenting the [USB protocol](https://github.com/dobra-noc/gm1356/blob/master/PROTOCOL.md) this device uses.

# Requirements
 - [hidapi](https://github.com/libusb/hidapi)
 - An OS which recognises the GM1356 as a USB device (ie. not OSX Big Sur).
 - A GM1356 sonometer (obviously)

# Usage

```text
bash$ ./howard -h
usage:  howard [OPTIONS] outputmode1 [ outputmode2 ... ]

Reads maximum noise level from a Benestar GM1356 sonometer
over a given interval, and optionally stores result in an
influxdb database.

Valid output modes are:
  short (single line to stdout)
  long  (multiple lines to stdout)
  db    (HTTP POST to influxdb, must also provide INFLUXDB OPTIONS - see below)

OPTIONS:
   -c           Run endlessly (also see -i and -w)
   -h           Show this usage text then exit.
   -i secs      Define time over which to get max decibels
   -t           Test mode - just probe for sononeter then exit
   -T           Influxdb test mode - just test influxdb connectivity then exit
   -w secs      Define period to wait between noise level checks
                insert will just be written to stdout.

INFLUXDB OPTIONS:
   -d dbname    Define influxdb database name
   -H hostname  Define influxdb hostname
   -p password  Define influxdb password
   -u username  Define influxdb password
   -y           Actually write to influxdb.  Without this,
```

# Graph of sample output

![sample output graph](https://cube.nethack.net/images/howard_graph.png "aircon.sh in action")

# Implementation Notes

 - The device seems to 'hang' periodically and cause all subsequent reads to timeout.  To work around this, after two concurrent timeouts I send an `IOCTL_USBDEVFS_RESET`.

 - I don't yet have configuration commands working, so the following need to be manually configured on the physical device:
  - slow/fast exponential time averaging
  - MAX mode
  - dBA vs dBC units