5.0 KiB
Integration into atomLibrary
This package contains a working C TCP core and native C bridge, not a compiled
CODESYS library. Target supplied: Raspberry Pi ARM64, runtime 4.16.0.0,
development environment SP22. ExtensionSDK inspected. See PI_SETUP.md for
the original generated-interface step. Real generated C/M4 files are now
supplied and the stub is implemented; use BUILD_ON_PI.md for the prepared build.
Do not map am_client directly to an IEC STRUCT: C int, size_t, alignment and
pointer sizes vary by target. Use SDK-generated external function signatures.
Implemented bridge API
The separate operations below are implemented as commands through ONE external
function, atMbCall_cext. See STATUS.md for command IDs and the status array.
The table describes operations rather than separate exported function names.
The bridge uses a fixed pool of contexts and returns generation-checked UDINT handles.
Zero is invalid. Use functions named with _cext for the Control SL Extension SDK:
| Function | Purpose |
|---|---|
| atMbOpen_cext | Allocate a fixed context slot; configure numeric IPv4 and port |
| atMbConfigure_cext | Set connect, response and reconnect times in milliseconds |
| atMbEnable_cext | Enable/disable recovery |
| atMbTick_cext | Advance one nonblocking step using monotonic time |
| atMbSubmit_cext | Validate and copy request/write data into the context |
| atMbGetStatus_cext | Copy explicitly sized status fields to IEC outputs |
| atMbCopyRead_cext | Copy validated read result with destination capacity check |
| atMbReconnect_cext | Cancel active transaction and create a fresh connection |
| atMbClose_cext | Close socket and release pool slot |
Only pass pointers during a synchronous call. Never store pointers into IEC application memory in C across scans or online changes. All operations for one handle must run from one task. Add target-specific lifecycle handling for stop, reset, download and online change; close or invalidate old handles before reuse.
Map existing function blocks
Keep the existing names and data interfaces, with these internal changes:
atMbClientTCP: own the C handle and call Tick once per scan. Keepin_ipAddress,in_port, request registration and priority scheduling. Changing the endpoint cancels the transaction and opens the new endpoint.atMbClient: schedule only while Ready and no request is pending. Complete the prior request and copy its read data BEFORE submitting the next request. Preserve priority ageing/minimum delay, adding explicit enabled eligibility and starvation checks. Enforce the existing 100-request registration limit.atMbReqBase: snapshot parameters when submitted; validate offset plus quantity against destination capacity. Reject overflow rather than silently truncate. Quantity zero means disabled at the wrapper level.atMbReadCoil/atMbReadDiscrete: FC01 / FC02; convert unpacked C uint16_t values to the actual IEC BOOL array type when copying.atMbReadHolding/atMbReadInput: FC03 / FC04, WORD values.atMbWriteCoil/atMbWriteHolding: FC15 / FC16; preservewriteNowsemantics. Snapshot write values on submit. A failed write is not automatically replayed; the application must explicitly decide whether to reissue it.atMbRequestStats: replaceModbusFB.Errorwith your own transport-error enum; keep Modbus exception separately. Keep counts, intervals and HMI indicators.atMbClientRTU: retain as a separate future transport; this C core does not implement serial RTU framing, CRC, timing or serial-port control.
Status additions
Client: state, connection attempt count, reconnect count, last transport error, OS socket error, active request index and last successful response time. Request: Busy/Done/Error, result, exception, consecutive successes/failures, last successful read time, hasValidData, dataAgeMs, stale and writeUncertain.
Use connection state for transport readiness. Use per-request successful read timestamps for freshness; another successful request must not refresh stale data. A valid exception proves the peer responded but does not validate data. Keep startup/never-read distinct from stale. The C core exposes a CLIENT-wide last_success timestamp; per-request timestamps belong in the scheduler wrapper.
Deployment gate
- Confirm PLC model, CODESYS runtime version, operating system and architecture.
- Confirm vendor support for custom C components; Control SL SDK support must not be assumed on a vendor-supplied PLC runtime.
- Generate the external declarations/stubs in the matching SDK, implement the bridge, compile for the actual target and package its component.
- Compile the IEC wrapper in CODESYS and exercise stop/start and online change.
- Bench-test unplug/replug, device restart, long outage, endpoint change, full request list, priority fairness and uncertain writes before site deployment.
References: