Physical floppy drives (FluxBridge)

Copperline can use a real 3.5" floppy drive connected to the host through a Greaseweazle USB controller in place of a disk image. The pure-Rust FluxBridge library, compiled into Copperline, talks to the hardware.

The bridge supplies the MFM data passing under the real drive’s head, and the emulated machine is otherwise unchanged: Paula’s disk DMA, trackdisk.device, and custom loaders work as they would on hardware.

Requirements¶

• A Greaseweazle board running firmware 0.27 or newer.

• A 3.5" PC or Shugart floppy drive and an appropriate data/power cable.

• Standard double-density (DD) or high-density (HD) floppy disks.

FluxBridge is compiled into Copperline by default. To build without physical drive support, leave out the fluxbridge feature (see Cargo features):

cargo build --release --no-default-features \
  --features "midi,frontend,wasm-boards,control,ctl-bin,import-uae-bin,net-nat,net-bridge,mt32,coppersynth,cpu-jit,profile-stats,game-library,mhi,cd-mp3,cd32-fmv,gdb,dap,netplay-internet,host-serial"

Configuration¶

In the launcher, open the Floppy tab and tick the Physical drive box for the desired bay (DF0: through DF3:), then press Configure.

In copperline.toml:

[floppy.df0]
bridge = "greaseweazle"      # "greaseweazle" (or "gw") or "off"
write_protected = true       # emulator-level write protection (default: true)
# bridge_port = "/dev/ttyACM0"   # serial port path (omit for auto-detection)
# bridge_cable = "a"             # "a"/"b" (PC cable) or "0".."3" (Shugart)
# bridge_density = "auto"        # "auto", "dd", or "hd"
# bridge_mode = "normal"         # "normal", "compatible", or "stalling"
# replay_speed = "fast"          # "fast" (default) or "normal"

From the command line:

copperline --model A500 --floppy-bridge df0 greaseweazle kickstart.rom

Serial port detection¶

By default, Copperline finds a connected Greaseweazle by itself. If more than one interface is plugged in, set bridge_port explicitly (for example /dev/ttyACM0 on Linux or COM3 on Windows).

Cable conventions and drive select¶

bridge_cable sets the drive select signal:

• a or b for standard IBM PC twisted floppy cables (drive A or B).

• 0 through 3 for straight Shugart cables.

Make sure this matches your cabling and the drive’s jumpers. Disk changes are detected directly on PC cables; on Shugart cabling, a swapped disk is noticed on the next read.

Density detection¶

bridge_density defaults to auto, which senses the density from the disk. Force dd or hd for non-standard disks, such as high-density media formatted as double-density.

Read modes¶

• normal (default): Capture starts as soon as the head settles, without waiting for the index pulse. A revolution captured off-index is joined where the recording repeats, and FluxBridge checks the join and the AmigaDOS track checksums before the track is kept in memory; an unverified capture is used for one pass only and then read again. (fast, the upstream name for this mode, is also accepted.)

• compatible: Captures from one index pulse to the next. Waiting for the index costs a little time, but non-standard and copy-protected tracks are reproduced exactly as recorded.

• stalling: Index-aligned like compatible, but the emulated machine waits until the track has been read. Use it only for timing-sensitive custom loaders that fail with the normal read latency.

bridge_mode = "turbo" is refused: that mode answers AmigaDOS calls instead of reading the disk.

Replay speed¶

Once a track is verified and kept in memory, replay_speed controls how fast later reads of that track are served:

• fast (default): Kept tracks are replayed at double speed. The first read always happens at the platter’s own rate.

• normal: Kept tracks are replayed at the normal rotational speed.

Write protection and disk writes¶

Writing to a physical disk needs both of these:

1. The disk’s own write-protect tab must be set to writable.

2. The configuration must set write_protected = false (or pass --floppy-bridge-writable).

Writes go straight to the physical disk as it turns, without the emulated machine waiting for them. A write of a full revolution can start at any rotational position, but a partial-track write that does not begin at the index pulse is refused, because the interface cannot place it accurately.

Operational differences from disk images¶

• Physical disk swapping: Insert and eject disks in the drive itself. The status bar shows the drive’s status and write-protection state.

• Drive sound effects: Copperline’s floppy drive sounds are off for bridged drives, since the real drive makes its own noise.

• Emulation pacing: A machine with a physical drive always runs at real speed, including headless capture runs, and refuses warp, because the real platter cannot be hurried.

• Determinism: Save states cannot capture the physical medium, and input recordings do not replay identically against a real drive.

Troubleshooting¶

• Device permissions (Linux): Your user account must belong to the dialout (or uucp / plugdev) group to open /dev/ttyACM*.

• Greaseweazle firmware: Copperline refuses firmware older than 0.27; update it with the official gw utility.

• Detailed diagnostic logging: Set COPPERLINE_DIAG_FLUXBRIDGE=1 in the environment to log head stepping, track capture and decoding, and seek timings.