Introduction

These examples act as Modbus/TCP server devices, responding to requests from Modbus/TCP clients by serving data through standard Modbus registers such as coils, discrete inputs, input registers, and holding registers. By using the NanoModbus library, developers can create lightweight, efficient Modbus/TCP servers suitable for embedded systems with limited resources.

The implementation consists of
- Modbus/TCP Stack
- NanoModbus Lib
- ENET ICSSG (Ethernet Driver)
- ENET CPSW (Ethernet Driver)
- LwIP TCP/IP networking stack with SNMP support on top of ethernet driver
- Modbus Server Application

Modbus/TCP Device Datasheet

Supported Modbus/TCP Functionality

Feature	Description	Implementation
Modbus/TCP Protocol	Supports the Modbus/TCP protocol for communication between devices.	Yes
Modbus Function Codes	Supports a wide range of Modbus functions	Yes
Modbus/TCP Server	The stack supports being a Modbus/TCP Server.	Yes
Modbus/TCP Client	The stack supports being a Modbus/TCP Client.	No
Exception Handling	Supports exception handling for Modbus requests.	Yes
Data Integrity	Supports CRC and error checking mechanisms.	No
Modbus/TCP over Ethernet	The stack works over standard Ethernet interfaces for Modbus/TCP.	Yes
Timeout Handling	Supports configurable timeout values for Modbus transactions.	Yes
Secure Modbus/TCP (SSL/TLS)	Secure Modbus/TCP connections over SSL/TLS.	No
Modbus/TCP over NanoModbus	Support for using Modbus/TCP in a lightweight, optimized stack.	Yes

Key Performance Parameters

Feature	Detail	Value
Maximum Connections	Number of simultaneous Modbus TCP connections	4
Response Time	Average time to respond to a Modbus request (from client to server)	> 200ms
Error Detection and Recovery	Modbus CRC error detection and error recovery mechanisms	No
Max Data Length	Maximum Modbus TCP message length supported	250 Bytes
Min Timeout Duration	Modbus TCP timeout duration	10ms
Max Coils read per second	Maximum number of coils that can be read per second	7957 coils
Max holding Registers read per second	Maximum number of registers(125) to be read per second	986 registers
Max Coils write per second	Maximum number of coils(1000) to be written per second	7986 coils
Max holding Registers write per second	Maximum number of registers(123) to be written per second	979 registers
Max Coils write per second	Maximum number of coils (1000) that can be written per second	7986 coils
Max Input Registers read per second	Maximum number of registers(125) to be read per second	995 registers
Max discrete Inputs read per second	Maximum number of registers(1000) to be read per second	7883 registers

General Stack Parameters

Supported Function Codes

Function Code	Description	Supported
01	Read Coils	Yes
02	Read Discrete Inputs	Yes
03	Read Holding Registers	Yes
04	Read Input Registers	Yes
05	Write Single Coil	Yes
06	Write Single Register	Yes
15	Write Multiple Coils	Yes
16	Write Multiple Registers	Yes

Stack Memory Usage

Demo Type	Code	RO Data	RW Data
Modbus Server CPSW	161,79kB	38,49kB	456,03kB

Steps to Run the Example

Build the example

When using CCS projects to build, import the CCS project for the required combination and build it using the CCS project menu, see Using SDK with CCS Projects).
When using makefiles to build, note the required combination and build using make command, see Using SDK with Makefiles)
Launch a CCS debug session and run the executable, see CCS Launch, Load and Run

HW Setup

Note: Make sure you have setup the EVM with cable connections as shown here, EVM Setup. In addition do below steps.

AM263PX-LP

Connect an ethernet cable to the AM243X-LP from host PC as shown below

Ethernet cable for ICSS based ethernet

Run the example

Attention: If you need to reload and run the example again, EVM power-cycle is MUST.

Launch a CCS debug session and run the example executable, see CCS Launch, Load and Run
You will see logs in the UART terminal as shown in the next section.
Note the IP address seen in the log, this is what we will use to communicate with the EVM.
Open the Modbus tester tool, set the device’s IP address and port, and send Modbus requests, for instance request read holding register

UART Log

The application shows a message New MODBUS client connected once a TCP client requests to connect.

Sample Output

==========================
  CPSW LWIP TCP CLIENT
==========================
EnetAppUtils_reduceCoreMacAllocation: Reduced Mac Address Allocation for CoreId:0 From 4 To 3
Open MAC port 1
EnetPhy_bindDriver:1935
PHY 3 is alive
PHY 12 is alive
Starting lwIP, local interface IP is dhcp-enabled
[LWIPIF_LWIP] NETIF INIT SUCCESS
Host MAC address-0 : 70:ff:76:1f:d0:19
[0]Enet IF UP Event. Local interface IP:0.0.0.0
[LWIPIF_LWIP] Enet has been started successfully
[0]Enet IF UP Event. Local interface IP:192.168.0.200
Waiting for network UP ...
Waiting for network UP ...
Waiting for network UP ...
Cpsw_handleLinkUp:1616
MAC Port 1: link up
[0]Network Link UP Event
Network is UP ...
 CPU load = 0 %
 CPU load = 0 %
New MODBUS client connected  70099AA0
 CPU load = 0 %

Communicate with the LP using ethernet

Firstly you can try to reach the LP using ping as shown below, using a command shell on the host PC
```
    > ping 192.168.0.200
```

Reference

Modbus Application Protocol Specification, v1.1b3