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Long CX II operations — listing a folder with many entries, downloading a file of any size — failed with a reported `Busy`. readPacket checksummed `transferred`, the byte count libusb returned, rather than `completeLength`, the length the packet declares. The calculator can hand back more bytes than the packet occupies (a 64-byte packet arriving as 65 was what showed up in tracing), and the stray byte failed the checksum. The packet was dropped and so never acked, the calculator retransmitted the same sequence number indefinitely, and the receive loop gave up after 40 reads. `transferred` was also wrong after the multi-chunk continuation loop, where it holds only the final chunk's size — the reason large stream transfers were unreliable. Also add NNSE retransmission to packet_send_cx2. A lost packet or lost ack was previously fatal, since the packet was written exactly once. Retries now carry the "not the first try" bit (reqAck bit 3) that TI's own stack sets, keeping the same seqno so the calculator can drop a duplicate. This path did not trigger in testing — every packet acked on the first attempt once the checksum was fixed — so its timeouts are deliberately generous to avoid retransmitting during slow flash writes. While here, zero `misc` and `unknown` instead of sending malloc garbage inside a checksummed header, and handle allocation failure. Verified against CX II firmware (0451:e022): `ls /` returns all 51 entries across 8 runs, a 193 KB download is byte-identical across two runs, and mkdir/rmdir round-trips. Note the error was never actually Busy. The libnspire crate (0.2.3) matches its positive NSPIRE_ERR_* constants against libnspire's negative return codes, so every error falls through to the libusb table and is mislabelled; -NSPIRE_ERR_INVALPKT and LIBUSB_ERROR_BUSY are both -6. That mismapping is upstream in the crate and is not addressed here. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
66 lines
3.2 KiB
Markdown
66 lines
3.2 KiB
Markdown
# nlink-cli — standalone TI-Nspire CX II link CLI (Linux)
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A GUI-free command-line build extracted from [n-link](https://github.com/lights0123/n-link),
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for transferring files to/from a TI-Nspire CX II (CAS) over USB on Linux.
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Built because:
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- **TiLP2** (distro `libticables` 1.3.6) does not support the CX II (USB PID `e022`) — its
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probe reports "no devices found".
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- The **prebuilt n-link 0.1.6 `.deb`** won't run on Ubuntu 26.04 (needs the retired
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`libssl.so.1.1` + WebKit2GTK 4.0). n-link is a Tauri/WebKit app.
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This CLI reuses only n-link's self-contained `cli.rs` (upload/download/ls/mkdir/rmdir/
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copy/move/upload-os), dropping Tauri/WebKit entirely.
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## Build
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```bash
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# one-time system deps
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sudo apt-get install -y libusb-1.0-0-dev pkg-config
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# Rust toolchain via rustup, then:
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cargo build --release
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# binary: target/release/n-link-cli
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```
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`Cargo.toml` uses a local `[patch.crates-io]` override of `libnspire-sys`
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(`../vendor/libnspire-sys`) whose CX II NNSE handshake retry limit is raised from 10.
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## Run
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```bash
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./target/release/n-link-cli ls /
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./target/release/n-link-cli download "/MyFile.tns" ./
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./target/release/n-link-cli upload ./MyFile.tns "/"
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./target/release/n-link-cli --help
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```
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## System setup required (Linux)
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1. **udev access** for the CX II (`/etc/udev/rules.d/70-ti-nspire.rules`):
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```
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SUBSYSTEM=="usb", ATTRS{idVendor}=="0451", ENV{ID_MM_DEVICE_IGNORE}="1"
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```
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(plus group/`uaccess` for PID `e022`) — then `udevadm control --reload-rules && udevadm trigger`.
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2. **ModemManager** grabs the interface on plug; the `ID_MM_DEVICE_IGNORE` rule above
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tells it to leave TI devices alone. Restart it after adding the rule:
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`sudo systemctl start ModemManager`.
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## The `Busy` error on CX II (fixed)
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Long operations against current CX II firmware — listing a folder with many entries,
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downloading a file of any size — used to fail with `Busy`. Two bugs in the vendored
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libnspire, both fixed in `vendor/libnspire-sys/libnspire/src/cx2.cpp`:
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1. **`readPacket` checksummed the wrong number of bytes.** It used the byte count the
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bulk transfer returned instead of the length the packet declares. The calculator can
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hand back more bytes than the packet occupies (a 64-byte packet arriving as 65), and
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the stray byte failed the checksum. The packet was then dropped and never acked, so
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the calculator retransmitted it forever until the receive loop gave up. The same
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variable was also wrong after a multi-chunk read, where it held only the last chunk's
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size — this is what made large stream transfers unreliable.
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2. **No retransmission.** A lost packet or lost ack was fatal; the packet was sent once
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and never repeated. It now retransmits with the "not the first try" bit (`reqAck` bit
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3) that TI's own stack uses, keeping the same sequence number.
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Note that the error was never really `Busy`: the `libnspire` **crate** (0.2.3, not this
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vendored C library) matches its positive `NSPIRE_ERR_*` constants against libnspire's
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negative return codes, so every error falls through to the libusb table and is
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mislabelled. `-NSPIRE_ERR_INVALPKT` is `-6`, and so is `LIBUSB_ERROR_BUSY`. A reported
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`Busy` is really `Invalid packet received`; `Timeout` is really `NACK received`, and so
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on. That mismapping is upstream in the crate and is **not** fixed here.
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