Library

nXPico W’s WiFi/lwIP network stack is reachable from ST through three routes:

SysSocket

Standard CODESYS system library — raw TCP/UDP sockets. Already part of CODESYS, nothing to install.

X.509 device identity

Firmware functions — generate the device key pair and certificate, read them back. Full reference →

MQTT / MQTTS

Firmware functions — publish/subscribe client, plain TCP or TLS with client-certificate authentication. Full reference →

The two neXo libraries, side by side

	nXPicoX509	nXPicoMQTT
What it gives you	Device identity: EC key pair and certificate generated on the board	MQTT client, plain TCP or TLS
Functions	8	8
nXPico	—	—
nXPico W	yes	yes
nXPico M	yes	no — the modem carries MQTT, see nXPico M › Modem
Needs the other one	no	for any TLS: the trust anchor is stored only if the device identity exists
File	precompiled	precompiled

Both are declaration-only: the code lives in the firmware, so installing them adds nothing to your application’s memory footprint. A board whose firmware does not carry a function rejects the download with an explicit error — it never fails quietly at runtime.

Installing the libraries

The X.509 and MQTT functions are implemented in the runtime, not in IEC code: these libraries declare them for you.

1. Download:
   • nXPicoX509.compiled-library
   • nXPicoMQTT.compiled-library
2. Tools → Library Repository → Install… → select the file → Close. Repeat for the other one.
3. Library Manager → Add Library… → search for nXPicoX509 / nXPicoMQTT.

Text parameters are pointers

Every text argument is a POINTER TO BYTE and must be passed with ADR() — for example mqttConnect(ADR(sHost), 8883, ADR(sClientId), ADR(sToken), ADR(''), TRUE). Passing a STRING directly makes the runtime read the first four characters as a memory address and crash (HardFault): the board stops responding and drops USB until it is power-cycled.

Return codes

All firmware functions share the runtime’s error codes:

Value	Name	Meaning
0	ERR_OK	done
1	ERR_FAILED	generic failure (usually: resource missing)
2	ERR_PARAMETER	invalid parameter
3	ERR_NOTINITIALIZED	a prerequisite is missing
10	ERR_PENDING	request accepted, result comes later
11	ERR_NUMPENDING	too many pending requests, retry
15	ERR_BUFFERSIZE	buffer too small, or data too large
17	ERR_NOMEMORY	queue full or out of memory

10 is not an error: it means the request was taken up and the outcome must be checked with the matching status function.