MIDI SysEx

About MIDI System Exclusive (SysEx) messages

If you're a MIDI expert, you can use SysEx messages (MIDI System Exclusive) to control the Axe-Fx II.

• To learn more about MIDI, see the article in Wikipedia
• To learn more about SysEx see this article in the Electronic Music Wiki.

SysEx messages for Ultra

• Ultra-specific SysEx information has been accurately acquired and organized by forum member GM Arts: here.
• Information about SysEx commands for retrieving Present/Effect bypass states is here.

Axe Fx II SysEx Information for loading IRs

The information below was provided by forum member LMO.

The Axe Fx II supports 2040-point impulse responses that are packaged for download in a series of 66 MIDI SysEx messages, as follows:

MIDI_START_IR_DOWNLOAD

Prepare the Axe-Fx II to receive impulse response data

Message Format:

0xF0 sysex start

0x00 manufacturing ID byte 0

0x01 manufacturing ID byte 1

0x74 manufacturing ID byte 2

0x03 model number

0x7A function ID

0x20

0x00

0x10

0xdd checksum

0xF7 sysex end

MIDI_G2_IR_DATA

There are 64 sysex messages, each containing 32 chunks of data. Each chunk consists of five bytes and can hold either four text characters or one 32-bit IR data sample.

The first data message sent includes 8 chunks of text that specify the 32-character IR name, and 24 chunks of IR data. The subsequent 63 data messages each contain 32 data samples for a total of 2040 samples.

Message Format:

0xF0 sysex start

0x00 manufacturing ID byte 0

0x01 manufacturing ID byte 1

0x74 manufacturing ID byte 2

0x03 model number

0x7B function ID

0x20

0x00

0xdd data chunk byte 0

0xdd data chunk byte 1

0xdd data chunk byte 2

0xdd data chunk byte 3

0xdd data chunk byte 4

--- 31 additional five byte data chunks ---

0xdd checksum

0xF7 sysex end

MIDI_CLOSE_IR_DOWNLOAD

Terminate the IR download sequence

Message Format:

0xF0 sysex start

0x00 manufacturing ID byte 0

0x01 manufacturing ID byte 1

0x74 manufacturing ID byte 2

0x03 model number

0x7C function ID

0xdd encoded checksum byte 0 for IR data

0xdd encoded checksum byte 1 for IR data

0xdd encoded checksum byte 2 for IR data

0xdd encoded checksum byte 3 for IR data

0xdd encoded checksum byte 4 for IR data

0xdd checksum

0xF7 sysex end

Data Chunk Encoding Scheme

The data encoding scheme translates four octets into five septets. Each septet occupies the lower seven bits of a byte, with the most significant bit set to 0.

• octet is one byte containing 8 bits of data
• septet is one byte containing 7 bits of data

byte_chunk = (data[0] & 0xFF )<< 24 | (data[1] & 0xFF )<< 16 | (data[2] & 0xFF )<< 8 (data[3] & 0xFF;

• convert four octets to five septets

septet[0] = byte_chunk & 0xFF;

septet[1] = byte_chunk >> 7 & 0xFF;

septet[2] = byte_chunk >> 14 & 0xFF;

septet[3] = byte_chunk >> 21 & 0xFF;

septet[4] = byte_chunk >> 28 & 0xFF;