Sigma fp-series USB protocol notes

← Overview

Interoperability notes for the camera-control mode of the SIGMA fp / fp L, as implemented in src/SigmaFp.Camera. They describe what the cameras do on the wire, verified on real fp and fp L bodies.

Transport

• USB still-image class interface; standard PTP (ISO 15740) bulk containers: [length u32][type u16: 1 command, 2 data, 3 response][code u16][transaction id u32][params].
• Driver: libusb-win32 (libusb0). Works on USB 2.0 (high-speed, 512-byte packets). On USB 3 SuperSpeed ports every transfer fails. Windows’ MTP driver makes the camera re-enumerate every few seconds.
• Session: GetDeviceInfo (0x1001), OpenSession (0x1002, transaction id 0), vendor operations, CloseSession (0x1003). Response 0x2001 = OK.
• A data phase whose length is a multiple of the packet size ends with a zero-length packet; one bulk read can contain the end of one container and the start of the next.

Vendor operations used

| Code | Operation | Data | |—|—|—| | 0x9035 | ConfigApi (param 0): enter camera-control mode | in: directory (tag 1 model, 2 serial, 3 firmware) | | 0x9012 / 0x9016 | Get / Set data group 1 (shutter, ISO) | see below | | 0x9017 | Set data group 2 (exposure mode, image quality) | | | 0x9018 | Set data group 3 (destination: PC) | | | 0x9024 | Set data group 4 (DNG bit depth) | | | 0x9032 | Set focus group | directory format | | 0x901B | Snap command | [0][mode][amount][0] | | 0x9015 | Capture status (param: image id) | [_][id][head][tail][status u16][dest][_] | | 0x901C | Clear capture entry (param: image id) | 10 zero bytes | | 0x902D | Picture file info | address @12, size @16, format @28, width/height @32/34, names from @36 | | 0x9022 | Partial picture file (params: address, offset, length) | [acquired u32][image bytes][~28-33 byte trailer] | | 0x902F | Close application (leave camera-control mode) | 10 zero bytes |

Data group SET messages: [0x00][field-present u16, big-endian][fields present, in order][0x00]. The camera’s own GET replies put the payload length in byte 0 and a checksum in the last byte; it accepts zeros in both positions on SET.

Examples:

• Group 1, shutter Bulb + ISO manual 400: 00 19 00 08 00 30 00
• Group 2, manual exposure + DNG: 00 04 80 04 10 00
• Group 3, save to PC: 00 00 80 02 00
• Snap non-AF: 00 02 01 00

Codes: shutter is 8-bit APEX in 1/3 steps (0x10 = 30 s … 0xA0 = 1/8000 s, 0x08 = Bulb); ISO is 8-bit APEX (0x30 = ISO 400; 0x20 = 100).

Capture flow

1. Set groups 2, 1, 4, 3 (mode, shutter/ISO, DNG depth, destination).
2. Read capture status (id 0) for head/tail, clear stale entries, and remember the tail as this shot’s id.
3. Snap non-AF (0x02).
4. Poll capture status for that id: 0x0001 exposing, 0x0004 processing, 0x0005 or 0x8003 ready; 0x6xxx failure (0x6001 AF failure, 0x6004 image generation failed).
5. Picture file info, then partial reads in chunks (8 MB): write exactly acquired bytes per chunk.
6. Clear the capture entry.

Long exposures (measured)

| Method | Result | |—|—| | Bulb + Snap Start Capture (0x06) / Stop Capture (0x07) | fails with 0x6001 (AF failure), also with manual focus set | | Bulb + Snap non-AF | exposes until the camera’s bulb limit (300 s); Stop Capture and a second release are ignored | | Bulb + external release on the 3.5 mm jack | does not work: ignored in API mode; outside API mode the jack works but the image goes to the card, which Camera Control mode does not expose (GetObjectHandles = 0) and Mass Storage mode cannot shoot. StartCapture (0x06) fails with 0x6001 AF failure, also without a lens and after StartAF |

Closing the session or the USB connection while the camera is exposing leaves it refusing captures (0x6004) until power-cycled.