mega-drive midi performance-testing performance-visualization

Mega MIDI Ping Pong

Measures performance of the Mega Drive MIDI Interface by sending it the "Ping" SysEx MIDI command and timing how long it takes for the "Pong" SysEx reply to be received.

Getting Started

Requirements

Golang 1.11

Usage

Build:

$ make

List MIDI devices:

$ go run ping_pong.go -list

ID: 0   Name: IAC Driver IAC Bus 1      Input: true     Output: false
ID: 1   Name: IAC Driver IAC Bus 2      Input: true     Output: false
ID: 2   Name: IAC Driver IAC Bus 1      Input: false    Output: true
ID: 3   Name: IAC Driver IAC Bus 2      Input: false    Output: true

Run with correct device IDs specified:

# go run ping_pong.go -in <input_device> -out <output_device>

$ go run ping_pong.go -in 0 -out 3

In: IAC Driver IAC Bus 1
Out: IAC Driver IAC Bus 2
2019-10-27T19:14:43.923466Z: Ping? Pong! (3.396952ms)
2019-10-27T19:14:44.12993Z: Ping? Pong! (20.398833ms)
2019-10-27T19:14:44.353178Z: Ping? Pong! (20.760178ms)
2019-10-27T19:14:44.577685Z: Ping? Pong! (19.596641ms)
2019-10-27T19:14:44.80165Z: Ping? Pong! (3.319763ms)
2019-10-27T19:14:45.00694Z: Ping? Pong! (5.519903ms)
2019-10-27T19:14:45.216816Z: Ping? Pong! (19.197244ms)
2019-10-27T19:14:45.440896Z: Ping? Pong! (18.86333ms)
2019-10-27T19:14:45.663128Z: Ping? Pong! (19.8471ms)
...

Help

$ go run ping_pong.go -h

Usage of ping_pong:
  -graph-filename string
        Graph Filename (default "results/output.png")
  -graph-title string
        Graph Title
  -in uint
        In Device ID
  -list
        List Devices
  -out uint
        Out Device ID

Theorectical Performance Limits

Serial Mode:

Max link speed = 4800 bps

4800 bps / (8 bits + 1 Start Bit + 1 Stop Bit = 10 bits per byte) = 480 bytes per second

Ping = F0 00 22 77 01 F7 = 6 bytes
Pong = F0 00 22 77 02 F7 = 6 bytes
------------------------------------
Total Ping+Pong Data Size = 12 bytes

480 / 12 = 40 Ping/Pong round trip per second

1000ms / 40 = 1 Ping/Pong round trip per 25 ms