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Waratah is a HID descriptor composition tool. It offers a high-level of abstraction, eliminates common errors (by design), and optimizes the descriptor to reduce byte size. It implements the HID 1.11 specification so developers don't have to.

It is expected to be used by device firmware authors during device bring-up.

Waratah uses a TOML-like hierarchical language of sections and keys to represent a HID Report Descriptor (Note: There is currently no support for HID Physical Descriptors). This can then be compiled to to either a simple plain-text format, or a C++ header file suitable for ingestion into device firmware.

Waratah is NOT a direct dt.exe replacement. dt.exe permits the use of specialized items (e.g. Push/Pop) and non-optimal practices (e.g. ReportSize larger than LogicalMinimum/Maximum). There are also known bugs in dt.exe, that have not been replicated in Waratah. It is reasonable to think of Waratah as high-level compiler like C and dt.exe as an assembler. No further development of dt.exe is planned.

Features

• Human-readable text for easy composition and meaningful source-control management.
• Inbuilt with all public Usages from HID Usage Table
• Composition of custom Vendor Usages.
• Inbuilt with all defined Units.
• Support for composition of new named Units.
• Comprehensive error messaging with line-level blame.
• C++ struct generation with context-aware variable-name generation.
• Optimistic descriptor optimization (redundant global items removed, and items combined).
• Report summary with itemized Id/Type/Size.
• Context-aware integer types bounds validation (ReportId, UsageId,...).
• Context-aware Usage type validation.
• Automatic generation of ReportIds.
• Automatic 8bit report alignment (padding inserted as needed).
• Automatic collection termination.
• Report Item size inferred from LogicalMin/Max (or vice-versa).
• Overspanning preventation, guaranteeing no item spans more than 4bytes (padding inserted as needed).
• Validate conditionally invalid Report Flags.
• Inline Usage transformation.
• Usage Range validation.

Example

Simple mouse with 3 buttons.

[[applicationCollection]]
usage = ['Generic Desktop', 'Mouse']

    [[applicationCollection.inputReport]]

        [[applicationCollection.inputReport.physicalCollection]]
        usage = ['Generic Desktop', 'Pointer']

            [[applicationCollection.inputReport.physicalCollection.variableItem]]
            usage = ['Generic Desktop', 'X']
            sizeInBits = 8
            logicalValueRange = 'maxSignedSizeRange'
            reportFlags = ['relative']

            [[applicationCollection.inputReport.physicalCollection.variableItem]]
            usage = ['Generic Desktop', 'Y']
            sizeInBits = 8
            logicalValueRange = 'maxSignedSizeRange'
            reportFlags = ['relative']

            [[applicationCollection.inputReport.physicalCollection.variableItem]]
            usageRange = ['Button', 'Button 1', 'Button 3']
            logicalValueRange = [0, 1]

Plain-text output

05-01....UsagePage(Generic Desktop[1])
09-02....UsageId(Mouse[2])
A1-01....Collection(Application)
85-01........ReportId(1)
09-01........UsageId(Pointer[1])
A1-00........Collection(Physical)
09-30............UsageId(X[48])
09-31............UsageId(Y[49])
15-80............LogicalMinimum(-128)
25-7F............LogicalMaximum(127)
95-02............ReportCount(2)
75-08............ReportSize(8)
81-06............Input(Data, Variable, Relative, NoWrap, Linear, PreferredState, NoNullPosition, BitField)
05-09............UsagePage(Button[9])
19-01............UsageIdMin(Button 1[1])
29-03............UsageIdMax(Button 3[3])
15-00............LogicalMinimum(0)
25-01............LogicalMaximum(1)
95-03............ReportCount(3)
75-01............ReportSize(1)
81-02............Input(Data, Variable, Absolute, NoWrap, Linear, PreferredState, NoNullPosition, BitField)
C0...........EndCollection()
95-01........ReportCount(1)
75-05........ReportSize(5)
81-03........Input(Constant, Variable, Absolute, NoWrap, Linear, PreferredState, NoNullPosition, BitField)
C0.......EndCollection()

C++ output

// AUTO-GENERATED by WaratahCmd.exe

#include <memory>

// HID Usage Tables: 1.3.0
// Descriptor size: 50 (bytes)
// +----------+-------+------------------+
// | ReportId | Kind  | ReportSizeInBits |
// +----------+-------+------------------+
// |        1 | Input |               24 |
// +----------+-------+------------------+
static const uint8_t hidReportDescriptor [] = 
{
    0x05, 0x01,    // UsagePage(Generic Desktop[1])
    0x09, 0x02,    // UsageId(Mouse[2])
    0xA1, 0x01,    // Collection(Application)
    0x85, 0x01,    //     ReportId(1)
    0x09, 0x01,    //     UsageId(Pointer[1])
    0xA1, 0x00,    //     Collection(Physical)
    0x09, 0x30,    //         UsageId(X[48])
    0x09, 0x31,    //         UsageId(Y[49])
    0x15, 0x80,    //         LogicalMinimum(-128)
    0x25, 0x7F,    //         LogicalMaximum(127)
    0x95, 0x02,    //         ReportCount(2)
    0x75, 0x08,    //         ReportSize(8)
    0x81, 0x06,    //         Input(Data, Variable, Relative, NoWrap, Linear, PreferredState, NoNullPosition, BitField)
    0x05, 0x09,    //         UsagePage(Button[9])
    0x19, 0x01,    //         UsageIdMin(Button 1[1])
    0x29, 0x03,    //         UsageIdMax(Button 3[3])
    0x15, 0x00,    //         LogicalMinimum(0)
    0x25, 0x01,    //         LogicalMaximum(1)
    0x95, 0x03,    //         ReportCount(3)
    0x75, 0x01,    //         ReportSize(1)
    0x81, 0x02,    //         Input(Data, Variable, Absolute, NoWrap, Linear, PreferredState, NoNullPosition, BitField)
    0xC0,          //     EndCollection()
    0x95, 0x01,    //     ReportCount(1)
    0x75, 0x05,    //     ReportSize(5)
    0x81, 0x03,    //     Input(Constant, Variable, Absolute, NoWrap, Linear, PreferredState, NoNullPosition, BitField)
    0xC0,          // EndCollection()
};

Unsupported Features

Currently unsupported (but desirable features).

• String Index Item
• Designator Item
• Array Item with non-contiguous Usages
• Explicit NULL values
• C++ generation of non-byte-aligned items
• Discrete Collection types
• Multi-level optimizations
• Windows hid.dll compliance and warnings