A40 hangs when attempting to flash

[casept]

ragnaroek log:

[DEBUG USB] Connected
[DEBUG DL] Handshaking
[TRACE USB] Send: [0x4F, 0x44, 0x49, 0x4E, ]
[TRACE USB] Recv blocking: [0x4C, 0x4F, 0x4B, 0x45, ]
[DEBUG DL] Handshake OK
[DEBUG SESS] Beginning session
[TRACE CMD] Cmd: SessionStart, Arg1: 0x0, Arg2: 0x4
[TRACE USB] Send: [0x64, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4, <1015 trailing 0's cut>]
[TRACE USB] Recv blocking: [0x64, 0x0, 0x0, 0x0, 0x0, 0x0, 0x3, <1 trailing 0's cut>]
[TRACE CMD] Cmd reply: SessionStart, Arg: 0x30000
[TRACE SESS] Version is newer than 1, negotiating packet size 1048576
[TRACE CMD] Cmd: SessionStart, Arg1: 0x5, Arg2: 0x100000
[TRACE USB] Send: [0x64, 0x0, 0x0, 0x0, 0x5, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, <1013 trailing 0's cut>]
[TRACE USB] Recv blocking: [0x64, <7 trailing 0's cut>]
[TRACE CMD] Cmd reply: SessionStart, Arg: 0x0
[DEBUG SESS] Negotiated session params: SessionParams { supports_compression: false, proto_version: V3, max_file_part_size: 1048576, max_seq_file_parts: 30, max_seq_size_bytes: 31457280, timeout: 120s }
[INFO  USB] Setting timeout: 120s
[INFO  PIT] Start PIT download
[DEBUG PIT] Initiating PIT download
[TRACE CMD] Cmd: TransferPIT, Arg1: 0x1
[TRACE USB] Send: [0x65, 0x0, 0x0, 0x0, 0x1, <1019 trailing 0's cut>]

[casept]

It seems like Odin sends the flash packet telling how many bytes to expect before doing the PIT download. Maybe we have to do the same?