MIDI SysEx

Axe Fx II SysEx Information

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

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 holds either four text characters or one IR data point.

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 points for a total of 2040 points.

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.

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1. octet is chunk data in octets
2. septet is a byte array of chunk data in septets

1. organize four bytes of input data in reverse order

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

1. convert four octets to five septets

septet[0] = octet & 0xFF; septet[1] = octet >> 7 & 0xFF; septet[2] = octet >> 14 & 0xFF; septet[3] = octet >> 21 & 0xFF; septet[4] = octet >> 28 & 0xFF;