Go iDot

Table of Contents

• Introduction
• Building
• Usage
  • btscan
  • showclock
  • showimage
  • startserver
• Known Limitations & Issues

Introduction

For a separate project, I have the need to display custom information on one of those cheap Aliexpress 32x32 iDotMatrix displays.

I initially went down the path of reverse engineering the iDotMatrix Android App, however after making some progress I found that derkalle4 has already made way more progress with their python3-idotmatrix-client project.

This repo contains a go implementation of a IDotMatrix client based on the excellent work of derkalle4 and the other contributors. So a big thanks to them all.

At this point, I don’t need any functionality other than what’s currently implemented (see below). However, I’m open to PRs if any gophers wish to contribute.

Building

There’s a simple CLI program to allow you to interact with your iDotMatrix display.

To build, simply run go build -o go-idot main.go in the root of this repo.

Usage

To get a full list of supported commands, run ./go-idot --help.

Top level help output

➜  go-idot git:(main) ✗ ./go-idot --help
A simple CLI application to interact with iDot displays

Usage:
  go-idot [command]

Available Commands:
  btscan      Displays a list of bluetooth devices that can be seen by the local adapter
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  showclock   Shows and optionally configures the clock of the iDot display
  showimage   Shows the supplied .png file on the iDot display
  startserver Start a simple rest API server

Flags:
  -h, --help   help for go-idot

Use "go-idot [command] --help" for more information about a command.
➜  go-idot git:(main) ✗

btscan

This sub commands allows you to scan for nearby Bluetooth devices to find the MAC of your iDotMatrix display. Look for a device with a name starting with IDM-.

btscan help output

➜  go-idot git:(main) ✗ ./go-idot btscan --help
Displays a list of bluetooth devices that can be seen by the local adapter

Usage:
  go-idot btscan [flags]

Flags:
  -h, --help               help for btscan
      --scan-time uint32   Max number of seconds to perform scan. 0 means infinite
      --verbose            Verbose output during scan
➜  go-idot git:(main) ✗

btscan example

➜  go-idot git:(main) ✗ ./go-idot btscan --scan-time 10
Scanning for 10 second(s)
Scan results
Address:CC:E6:BA:14:F8:EA  RSSI:  0  Name:BT5.0 Mouse
Address:60:81:6E:82:50:58  RSSI:-54  Name:IDM-825058
Address:47:EC:47:FD:E0:4B  RSSI:-60  Name:
Address:3C:E0:02:9A:CD:90  RSSI:-92  Name:
Address:DC:2C:26:3A:C2:58  RSSI:  0  Name:Keychron K2
➜  go-idot git:(main) ✗

showclock

This sub command allows you do put the iDotMatrix display in to clock mode and configure what that clock looks like.

showclock help output

➜  go-idot git:(main) ✗ ./go-idot showclock --help
Shows and optionally configures the clock of the iDot display

Usage:
  go-idot showclock [flags]

Flags:
      --24hour          Show time in 24 hour format (default true)
  -h, --help            help for showclock
      --show-date       Show date as well as time (default true)
      --style int       Style of clock. 0:Default 1:Christmas 2:Racing 3:Inverted 4:Hour Glass (default 4)
      --target string   Target iDot display MAC address
      --time string     Time value in RFC1123Z format. As per 'date -R'
➜  go-idot git:(main) ✗

In it’s most basic usage, you simply need to supply the --target option specifying the MAC address as found in btscan.

showclock to set current wall time wihh default display values

➜  go-idot git:(main) ✗ ./go-idot showclock --target 60:81:6E:82:50:58
➜  go-idot git:(main) ✗

showclock to set a specific time

➜  go-idot git:(main) ✗ ./go-idot showclock --target 60:81:6E:82:50:58 --time "Thu, 21 Feb 2024 07:30:36 +0000"
➜  go-idot git:(main) ✗

showimage

This sub command allows you to show arbitrary (see known limitations below) images on the display.

showimage help output

➜  go-idot git:(main) ✗ ./go-idot showimage --help
Shows the supplied .png file on the iDot display

Usage:
  go-idot showimage [flags]

Flags:
  -h, --help                help for showimage
      --image-file string   Path to a 32x32 .png image file
      --target string       Target iDot display MAC address
➜  go-idot git:(main) ✗

To display an image, simply supply its path using the --image-file argument

Show an image

./go-idot showimage --target 60:81:6E:82:50:58 --image-file testdata/demo_32.png

startserver

This sub commands starts up a simple RESTful API server that allows the above operation to be remotely invoked.

startserver help output

➜  go-idot git:(main) ✗ ./go-idot startserver --help
Start a simple rest API server

Usage:
  go-idot startserver [flags]

Flags:
  -h, --help            help for startserver
      --port uint       Port to listen on (default 8080)
      --target string   Target iDot display MAC address
➜  go-idot git:(main) ✗

To start server listening on default port of 8080, Ctrl+C to quit.

Note	The server maintains a Bluetooth connection whilst running.

➜  go-idot git:(main) ✗ ./go-idot startserver --target 60:81:6E:82:50:58
Connecting to 60:81:6E:82:50:58
Connected
Listing at :8080

showclock RESTful endpoint

The endpoint at /api/v1/showclock provides a means to show the clock.

To use it, POST a json document as shown below. The fields match the arguments of the showclock sub command.

json shown will default values

{
  "time"     :"",
  "style"    :0,
  "showdate" :false,
  "show24h"  :false
}

Set the clock to the current wall time with default values (i.e. empty document)

curl -X POST -H "Content-Type: application/json"  http://localhost:8080/api/v1/showclock

Set the clock to the specified time, show date, and display time in 24h format

curl -X POST -H "Content-Type: application/json" -d '{"time":"Tue, 20 Feb 2024 16:23:07 +0000", "showdate": true, "show24h": true}' http://localhost:8080/api/v1/showclock

showimage RESTful endpoint

The endpoint at /api/v1/showimage provides a means to display an image.

To use it, POST a form specifying the image file to be uploaded.

Image upload

curl -F "imgfile=@testdata/doll_32.png;type=image/png" http://localhost:8080/api/v1/showimage

Known Limitations & Issues

• Currently only using the default Bluetooth adapter.

• Only tested with 32x32 iDotMatrix display. Showimage checks that image is 32x32.

• Only test on Linux

• Fix issue where write MTU gets incorrectly discovered, currently I override it to 514 in func (d *Device) Write(packet []byte) error