Layer: L7 Application · Build flags: PC_ENABLE_LSV2

What this example teaches

Heidenhain TNC controls (iTNC 530, TNC 320 / 620 / 640, ...) speak LSV/2 for DNC and data access - file transfer, program upload/download, and run/status inspection - over a serial link or, as here, LSV/2-over-TCP (default port 19000). It is the CNC-native way to pull live machine state from the common European control with no vendor middleware. services/lsv2 is a pure codec for the telegram framing; the sketch owns the socket.

Every LSV/2 telegram is a 4-byte big-endian payload-length prefix, a 4-character mnemonic, then the payload. The length counts the payload only, so a bare acknowledgement is exactly 8 bytes:

A_LG "INSPECT\0"     ->  00 00 00 00 T_OK            (access granted)
R_RI <EXEC_STATE=23> ->  00 00 00 NN S_RI <payload>  (run-info data)   or  ... T_ER <class> <code>
A_LO                 ->  00 00 00 00 T_OK            (rights dropped)

The codec frames each request and slices each reply off the byte stream:

pc_lsv2_build_login(tx, sizeof(tx), PC_LSV2_LOGIN_INSPECT, nullptr); // A_LG "INSPECT\0"
pc_lsv2_build_run_info(tx, sizeof(tx), LSV2_RI_EXEC_STATE);           // R_RI <2-byte selector>
pc_lsv2_build_filename(tx, sizeof(tx), PC_LSV2_CMD_FILE_LOAD, "PGM.H"); // R_FL "PGM.H\0"
Lsv2Telegram r;  size_t used;  pc_lsv2_parse(rx, n, &r, &used);       // one telegram off the stream
pc_lsv2_is_ok(&r);                                                    // T_OK?
pc_lsv2_error(&r, &err_class, &err_code);                             // T_ER / T_BD 2-byte error

Access is privilege-gated: log in to a group (INSPECT to read, FILE for the file system, DNC for DNC functions, ...) with A_LG, then issue commands; the control answers T_OK / T_FD, a S_* data reply, or T_ER / T_BD carrying a two-byte error-class + error-code.

Prerequisites (a Heidenhain control, or a simulator)

Point TNC_IP at a TNC with the LSV/2 / DNC Ethernet interface enabled (the control's network / DNC settings). No machine handy? The pyLSV2 project ships a small LSV/2 server stub, or a socket server that answers each request with the 00 00 00 00 T_OK / S_RI frames above works for a dry run.

Build and run

pio ci --board=esp32dev --project-option="framework=arduino" \
  --project-option="build_flags=-DPC_ENABLE_LSV2=1" \
  --lib="." examples/L7-Application/HeidenhainLsv2/HeidenhainLsv2.ino

Flash and watch Serial @ 115200:

IP: 192.168.1.42
[lsv2] login INSPECT: T_OK
[lsv2] exec-state: S_RI, 2 payload bytes: 00 03
[lsv2] selected-pgm: S_RI, 24 payload bytes: 54 4E 43 3A 5C ...
[lsv2] override: S_RI, 6 payload bytes: 00 64 00 64 00 64
[lsv2] done

Annotated source

The complete sketch is HeidenhainLsv2.ino. The codec itself is in src/services/machine_tool/lsv2/lsv2.h; the telegram framing, the command / response mnemonic set, and the login / filename / run-info payload layouts are cross-checked byte-for-byte against the pyLSV2 reference. Pairs with the HaasMdc and Fanuc FOCAS machine-tool examples.