CSP protocol is seemingly designed specifically for Smart Pianist app.

From the app point of view the piano is as a set of properties. Most properties are arrays. The properties can be of two types: integer or string. The app can change the properties or read their values.

For example there is a property for current playback position of the MIDI-song. The app can change it by sending SET-message for POSITION-property to the piano. This property is also automatically changed by piano during playback. The app can activate events for this property; then the piano will send messages to the app every time the playback position is changed.

Message types (actions)

The app can send to piano messages of the following types:

• SET - set property;
• GET - get property;
• RESET - reset property to default value;
• EVENTS - enable events for property changes.

The piano can send to app messages of the following types:

• INFO - response to GET message or when a property is changed and events are enabled for that property;
• SET-RESULT - response to SET message; the message contains result code (error code) and new property value;
• EVENTS-ON - response to EVENTS message, confirming activation of events for property.

All messages of one type have the same format, which is independent of the property.

Embedding CSP Message into MIDI message

CSP messages are sent within MIDI SysEx messages:

f0 43 73 01 52 25 26 <CSP-Message> f7

Here:

• Leading f0 and trailing f7 are enclosing bytes for all SysEx messages;
• 43 is the manufacturer code of Yamaha;
• 73 01 52 25 26 is a prefix for all CSP-messages;
• CSP-Message is explained below.

Format for CSP-messages

All messages start with two bytes of message type signature, followed by four bytes of property id signature:

• Type-Id (2 Bytes)
• Property-Id (4 Bytes)

Depending on message type an additional data is followed.

SET

• 01 01
• Property-Id (4 Bytes)
• Index (1 Byte)
• 01 00
• Value length (2 bytes)
• Value (variable length)

GET

• 01 00
• Property-Id (4 Bytes)
• Index (1 Byte)
• 01 00

INFO

• 00 00
• Property-Id (4 Bytes)
• Index (1 Byte)
• 01 00
• Value length (2 bytes)
• Value (variable length)

SET-RESULT

• 00 01
• Property-Id (4 Bytes)
• Index (1 Byte)
• 01 00
• Error code (2 bytes)
• Value length (2 bytes)
• Value (variable length)

RESET

• 04 01
• Property-Id (4 Bytes)
• Index (1 Byte)
• 01 00

EVENTS

• 02 00
• Property-Id (4 Bytes)

EVENTS-ON

• 02 01
• Property-Id (4 Bytes)

Property-Ids

• Piano-Model: 0f 01 18 01
• Firmware-Version: 0f 01 0b 01
• Playback-Position: 04 00 0a 01
• Stream-Lights (on/off): 04 02 00 01
• Stream-Lights-Speed (slow/fast): 04 02 02 01

and so on. I'm not listing all properties here. For a more complete list please see the source code unit PianoMessage.cpp.

Index

Index is the third part for all messages except of EVENTS. What it means depend on property. For example for property Volume the index refers to channel. For property Part index identifies right hand, left hand or backing. Please refer to the source code unit PianoMessage.cpp for details for each property.

Error Code

This field is present only in message-type SET-RESULT which is sent by piano as a response to SET-message. The error code indicates if the operation succeeded.

• 00 00 - property value changed successfully (or it was already set to this value);
• 02 02 - index out of range;
• 02 04 - value out of range;
• 02 05 - read-only property;
• 02 07 - value cannot be used in this context;
• other codes are possible.

Value Length

Value length specifies how many bytes are occupied by the field value. Value length takes two bytes. These are typical 7-bit MIDI-bytes (not normal 8-bit bytes).

Value

• Integer - for integer properties it can be 1 to 4 bytes long. These are typical 7-bit MIDI-bytes (not normal 8-bit bytes).
• Struct/record - some properties contains more bytes, they can be interpreted as structs (records). For example property Loop consists of 9 bytes. First byte identifies if the Repeat-Loop is active. Then four bytes for the start of the fragment and another four bytes for the end of it.
• String - string data is encoded for 7-bit MIDI-bytes compatibility. Every 7 characters of the string is preceded by one byte, where each bit contains the highest bit of the character. See encoding and decoding routines.

Examples

Send message to switch guide mode on

f0 43 73 01 52 25 26 01 01 04 03 00 01 00 01 00 00 01 01 f7

What we have here:

• f0 - SysEx-prefix;
• 43 73 01 52 25 26 - CSP-prefix;
• last byte f7 - SysEx suffix

The remaining CSP-message:

01 01 04 03 00 01 00 01 00 00 01 01

Here:

• 01 01 - id of SET-message type;
• 04 03 00 01 - id of the Guide-property;
• 00 - index is 0 for this simple property;
• 01 00 - constant (is always there);
• 00 01 - length of the followed value. For this property it's one byte;
• 01 - value the property should be set to. For the guide property value 01 means On and value 00 means Off.

Send message asking if guide mode is on or off

If we want to determine wether the guide mode is on or off we can send the message of GET-type

f0 43 73 01 52 25 26 01 00 04 03 00 01 00 01 00 f7

The actual CSP-message here is:

01 00 04 03 00 01 00 01 00

• 01 00 - id of GET-message type;
• 04 03 00 01 - id of the Guide-property;
• 00 - index is 0 for this simple property;
• 01 00 - constant (is always there).

When the piano receives this message it sends another message back to us. That other message contains the info about current value of guide property:

Info about guide mode

f0 43 73 01 52 25 26 00 00 04 03 00 01 00 01 00 00 01 01 f7

This message is very similar to our SET-message except that the message-type is 00 00. All other fields are the same.

CSP-message:

00 00 04 03 00 01 00 01 00 00 01 01

Here:

• 00 00 - id of INFO-message type;
• 04 03 00 01 - id of the Guide-property;
• 00 - index is 0 for this simple property;
• 01 00 - constant (is always there);
• 00 01 - length of the followed value. For this property it's one byte;
• 01 - value the property. 01 means guide mode is currently On.