Add MIDI echo example to the README.md

Author: esp32beans

README.md

@@ -1,17 +1,21 @@
 # ESP32-S2 and ESP32-S3 USB MIDI Example for Arduino
 
+For lots more debug output, set the Debug Core Level to Verbose. This can
+drastically slow the code so do not do this when speed matters.
+
+## examples/ESP32USBMIDI
+
 This program is based on an ESP-IDF TinyUSB USB MIDI example with minimal
 changes so it works with arduino-esp32. See https://github.com/espressif/esp-idf/blob/master/examples/peripherals/usb/device/tusb_midi/main/tusb_midi_main.c
 for the original code.
 
 The board must be reset or power cycled to make the new code take effect. This
-has been tested on ESP32-S3 and ESP32-S2 DevKit boards ("ESP32S3 Dev Module"
+has been tested on ESP32S3 and ESP32S2 DevKit boards ("ESP32S3 Dev Module"
 and "ESP32S2 Dev Module").
 
 USB Mode must be set to USB-OTG (TinyUSB) on ESP32S3.
 
-For lots more debug output, set the Debug Core Level to Verbose. It helps to be
-familiar with the ESP-IDF API.
+Some knowledge of the ESP-IDF API is helpful to understand the code.
 
 Example of output on the Arduino IDE Serial monitor.
 The computer connected to the ESP32S3 sends MIDI Start, Stop, and CC 7 0.
@@ -41,3 +45,53 @@ channel  1   note-off          A4   0
 channel  1   note-on          F#5 127
 channel  1   note-off          D5   0
 ```
+
+## examples/ESP32USBMIDIECHO
+
+This program echos USB MIDI back to the source. There is very little serial console output.
+
+SendMIDI and ReceiveMIDI are command line MIDI programs for Windows, MacOS, and Linux.
+
+* https://github.com/gbevin/ReceiveMIDI
+* https://github.com/gbevin/SendMIDI
+
+In one terminal windows, get ready to show received MIDI with timestamps.
+```
+$ receivemidi list
+Midi Through Port-0
+ESP32S3_DEV MIDI 1
+$ receivemidi dev ESP32S3_DEV timestamp
+```
+
+In another terminal window, send MIDI start and stop.
+```
+$ sendmidi list
+Midi Through Port-0
+ESP32S3_DEV MIDI 1
+$ sendmidi dev ESP32S3_DEV start stop
+```
+
+On the receive window, something similar to this should appear.
+```
+13:18:25.506   stop
+13:18:25.507   start
+```
+
+Try sending MIDI panic to see what it does.
+```
+$ sendmidi dev ESP32S3_DEV panic
+```
+
+panic sends note off to all 16 channels and for all 128 notes plus CC 64 0, CC 120, 0, and CC 123 0.
+
+receivemidi should show something like this. This is the start of a very long
+listing.
+```
+13:22:32.791   channel  1   control-change    64     0
+13:22:32.792   channel  1   control-change   120     0
+13:22:32.793   channel  1   control-change   123     0
+13:22:32.794   channel  1   note-off         C-2   0
+13:22:32.795   channel  1   note-off        C#-2   0
+13:22:32.796   channel  1   note-off         D-2   0
+13:22:32.797   channel  1   note-off        D#-2   0
+```

examples/ESP32USBMIDIECHO/ESP32USBMIDIECHO.ino

@@ -92,7 +92,7 @@ void setup() {
   USB.begin();
   while (!Serial && millis() < 5000)
     delay(10);
-  // Read recieved MIDI packets then write them out
+  // Read received MIDI packets then write them out
   ESP_LOGI(TAG, "MIDI echo task");
   xTaskCreate(midi_echo, "midi_echo", 2 * 1024, NULL, 5, NULL);
 }