ROLI Blocks Protocol

ROLI never documented their Blocks protocol. Everything in this section was reverse-engineered from the JUCE SDK source code (the roli_blocks_basics module) and the extracted ROLI Connect Electron app.

The protocol is a proprietary binary format layered on top of standard USB MIDI. All control messages are MIDI System Exclusive (SysEx) packets with ROLI's manufacturer ID, 7-bit packed payloads, and a custom checksum. It's compact, efficient, and surprisingly well-designed for what is essentially a bitstream squeezed through a 7-bit pipe.

Protocol Stack

graph TB
    subgraph "Application Layer"
        CMD[Device Commands]
        CFG[Config Messages]
        TOUCH[Touch Events]
        TOPO[Topology Messages]
        DATA[Data Change / LED]
    end
    subgraph "Protocol Layer"
        BUILD[Packet Builder]
        DECODE[Packet Decoder]
        PACK[7-bit Packing]
        CSUM[Checksum]
    end
    subgraph "Transport Layer"
        SYSEX[SysEx Framing]
        MIDI[USB MIDI]
    end
    CMD --> BUILD
    CFG --> BUILD
    TOUCH --> DECODE
    TOPO --> DECODE
    DATA --> BUILD
    BUILD --> PACK
    DECODE --> PACK
    PACK --> CSUM
    CSUM --> SYSEX
    SYSEX --> MIDI

Key Concepts

SysEx Framing

Every message is wrapped in a MIDI SysEx envelope with ROLI's manufacturer ID (00 21 10) and a product byte (77 for Blocks). The first payload byte encodes both the topology index and message direction. See SysEx Framing for the full format.

7-bit Packing

MIDI is a 7-bit protocol: byte values above 127 are reserved for status messages. The Blocks protocol packs arbitrary binary data into 7-bit bytes using an LSB-first scheme where values span byte boundaries as needed. This is the single most critical piece of the protocol to implement correctly, and the #1 source of bugs during development. One off-by-one in the bit cursor and every field after it decodes as garbage. See the SysEx Framing section for the algorithm.

Topology Indexing

Each device in a connected topology gets a 7-bit index. Index 0 is the master (USB-connected) device. DNA-connected devices get indices 1+. The broadcast index 63 addresses all devices.

Bidirectional Messages

Messages flow in both directions. Host-to-device messages include commands (begin/end API mode, ping), configuration writes, LED data, and firmware updates. Device-to-host messages include topology reports, touch events, button events, packet ACKs, and log messages. See Message Types for the full catalog.

Protocol Constants

Constant	Value	Description
ROLI_SYSEX_HEADER	F0 00 21 10 77	Standard Blocks SysEx header
SERIAL_DUMP_REQUEST	F0 00 21 10 78 3F F7	Serial number request
SERIAL_RESPONSE_HDR	F0 00 21 10 78	Serial response header
RESET_MASTER	F0 00 21 10 49 F7	Master device reset
PROTOCOL_VERSION	1	Protocol version byte
TOPOLOGY_INDEX_BROADCAST	63	Broadcast to all devices
API_MODE_PING_TIMEOUT_MS	5000	Device timeout without ping

USB Device Identification

ROLI devices use vendor ID 0x2AF4. blocksd identifies devices by scanning MIDI port names for "BLOCK" or "Block". USB IDs are reference information; the detector does not consult sysfs.

USB PID	Device
0x0100	Seaboard (original)
0x0200	Seaboard RISE 25
0x0210	Seaboard RISE 49
0x0700	Seaboard Block
0x0900	Lightpad Block
0x0E00	LUMI Keys / Piano M
0x0F00	ROLI Piano (49-key)
0x1000	ROLI Airwave Pedal

Deep Dives

• SysEx Framing: packet structure, checksum algorithm, and the 7-bit packing engine
• Message Types: complete catalog of all host-to-device and device-to-host messages
• Topology: how DNA mesh networking works at the wire level
• Connection Lifecycle: the full state machine from port scan to keepalive loop