Getting Started

nXPlc runs the same CODESYS Control runtime as the rest of the family, with one difference that changes how you program it: it has no process I/O. You will not find inputs and outputs to map — you will find a CAN bus to open.

The board must already be running the runtime before you open CODESYS.

1. Install the device description

1. Download CODESYS_Control_nXPlc.devdesc.xml.
2. In CODESYS: Tools → Device Repository → Install…
3. Select the file and confirm.

Name	nXPlc
Vendor	nexo S.r.l.
Device ID	167e 2008
Version	3.5.20.200

2. Create the project

1. File → New Project… → Standard project.
2. Choose nXPlc.
3. An IO module appears under the device node with the local channels — power diagnostics, indicators and die temperature. See IO Mapping.

3. Connect over Ethernet

CODESYS talks to nXPlc over the network. A new board answers on 192.168.1.50: give the PC an address in the same subnet (for example 192.168.1.10, mask 255.255.255.0), then in Communication Settings scan the network or type 192.168.1.50 as the device address. Changing the address, DHCP and the rest are in Ethernet.

At the first login CODESYS asks you to create the administrator user: the board has no default users or passwords. See Users and Passwords.

4. The CAN bus

CAN is used with the standard CODESYS tools, in two ways:

• Devices in the tree — under nXPlc: Add Device… → CANbus (network 0, same bit rate as the other nodes), then under the CANbus the CANopen Manager and its slaves. This is the way for CANopen.
• Raw frames from ST — the CAA CanL2 library, with no nodes in the tree: network and bit rate are parameters of the open call.

hDriver := CL2.DriverOpenP(0, 500, FALSE, szMem, ADR(abMem), ADR(eError));
(*                         ^    ^                                        *)
(*                      network kbit/s                                   *)

Both are described in CAN Bus.

5. Add the libraries

In the Library Manager, Add Library…, you need three entries:

Library	Version	Namespace
CAA Types Extern	3.5.17.0	CAA
CAA CanL2 Extern	3.5.17.0	CL2
CAA Can Low Level Imp Extern	3.5.17.0	CL2I

Adding CAA Types Extern pulls in its dependencies on its own. Without these three, the types CAA.HANDLE, CL2.ERROR and CL2I.COBID do not exist and the project will not compile.

6. First program

The shortest one that proves the bus is alive:

PROGRAM PLC_PRG
VAR
    szMem   : CAA.SIZE;
    abMem   : ARRAY[0..1023] OF DWORD;
    hDriver : CAA.HANDLE;
    eError  : CAA.ERROR;
    eState  : CL2.BUSSTATE;
END_VAR

IF hDriver = 0 THEN
    szMem   := CL2.DriverGetSize(0, FALSE, 16, ADR(eError));
    hDriver := CL2.DriverOpenP(0, 500, FALSE, szMem, ADR(abMem), ADR(eError));
ELSE
    eState := CL2.GetBusState(hDriver, ADR(eError));
END_IF

A non-zero hDriver means the controller is configured and the bus is open. From there, CAN Bus explains how to transmit and receive.

Task period

The MainTask period is how often your application sees the bus. 100 ms is a good starting point; the runtime moves messages out of the controller once per millisecond, so below 1 ms you gain nothing.

You can have at most 3 cyclic tasks: a fourth one is refused with an error at download or at startup. Priorities are honoured: a higher-priority task interrupts a lower-priority one that is running.

Division by zero

A 32-bit integer division (INT, DINT, UDINT, …) by zero returns 0 with no exception: that is how the Cortex-M33 processor behaves. A 64-bit division (LINT, ULINT, LWORD) by zero, and floating-point errors computed in software, put the application into an exception instead (EXCEPTION state in the IDE); the runtime stays reachable. To catch the 32-bit division as well, use CODESYS’s POUs for implicit checks (CheckDivDInt, CheckDivInt, CheckDivReal, CheckDivLReal, …).

What is not there

Serial ports for the application. COM2 would land on the CAN controller’s SPI pins and is refused; the other UART is the RS422 bus of the IO-Locali modules. An nXPlc application has no serial ports, and there is no serial log either: diagnostics are read in the device Log in CODESYS.

SIL2 and SoftMotion. They can be inserted in the tree, but the target does not support them. The CANopen Manager works (see CAN Bus); the CANopen Device has not been tested yet.