## MyEMS Modbus TCP Service

### Introduction

This service is a component of MyEMS to acquire data from Modbus TCP devices.

### Dependencies

mysql-connector-python

modbus_tk

schedule

python-decouple

telnetlib3

### Quick Run for Development

```bash
cd myems/myems-modbus-tcp
pip install -r requirements.txt
cp example.env .env
chmod +x run.sh
./run.sh
```

### Installation

### Option 1: Install myems-modbus-tcp on Docker

Refer to [myems.io](https://myems.io/docs/installation/docker-linux#step-4-myems-modbus-tcp)

### Installation Option 2: Online install on Ubuntu server with internet access

Refer to [myems.io](https://myems.io/docs/installation/debian-ubuntu#step-4-myems-modbus-tcp)

### Installation Option 3: Offline install on Ubuntu server without internet access

Download and install MySQL Connector:
```bash
cd ~/tools
wget https://cdn.mysql.com//Downloads/Connector-Python/mysql-connector-python-8.0.28.tar.gz
tar xzf mysql-connector-python-8.0.28.tar.gz
cd ~/tools/mysql-connector-python-8.0.28
python3 setup.py install
```

Download and install Schedule
```bash
cd ~/tools
git clone https://github.com/dbader/schedule.git
cd ~/tools/schedule
python3 setup.py install
```

Download and install Python Decouple
```bash
cd ~/tools
git clone https://github.com/henriquebastos/python-decouple.git
cd ~/tools/python-decouple
python3 setup.py  install
```

Download and install modbus-tk
```bash
cd ~/tools
git clone https://github.com/pyserial/pyserial.git
cd ~/tools/pyserial
python3 setup.py install
git clone https://github.com/ljean/modbus-tk.git
cd ~/tools/modbus-tk
python3 setup.py install
```

Install myems-modbus-tcp service
```bash
cp -r myems/myems-modbus-tcp /myems-modbus-tcp
cd /myems-modbus-tcp
```
Create .env file based on example.env and edit the .env file if needed:
```bash
cp /myems-modbus-tcp/example.env /myems-modbus-tcp/.env
nano /myems-modbus-tcp/.env
```
Setup systemd service:
```bash
cp myems-modbus-tcp.service /lib/systemd/system/
```
Enable the service:
```bash
systemctl enable myems-modbus-tcp.service
```
Start the service:
```bash
systemctl start myems-modbus-tcp.service
```
Monitor the service:
```bash
systemctl status myems-modbus-tcp.service
```
View the log:
```bash
cat /myems-modbus-tcp.log
```

### Add Data Sources and Points in MyEMS Admin UI

NOTE: If you modified Modbus TCP data sources and points, please restart this service:
```bash
systemctl restart myems-modbus-tcp.service
```

Input Data source protocol: 
```
modbus-tcp
```
Data source connection example:
```
{"host":"10.9.67.99","port":502,"interval_in_seconds":60]}
```

Point address example:
```
{"slave_id":1, "function_code":3, "offset":0, "number_of_registers":2, "format":"<f", "byte_swap":true}
```

### Address 

#### slave_id
    The slave ID

#### function_code
```
    01 (0x01) Read Coils
    02 (0x02) Read Discrete Inputs
    03 (0x03) Read Holding Registers
    04 (0x04) Read Input Registers
    23 (0x17) Read/Write Multiple registers
```

#### offset
    The starting register address specified in the Request PDU

#### number_of_registers
    The number of registers specified in the Request PDU

#### format
Use python3 library struct to format bytes.
Python bytes objects are used to hold the data representing the C struct
and also as format strings (explained below) to describe the layout of data in the C struct.

The optional first format char indicates byte order, size and alignment:
    @: native order, size & alignment (default)
    =: native order, std. size & alignment
    <: little-endian, std. size & alignment
    >: big-endian, std. size & alignment
    !: same as >

The remaining chars indicate types of args and must match exactly;
these can be preceded by a decimal repeat count:
    x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;
    ?: _Bool (requires C99; if not available, char is used instead)
    h:short; H:unsigned short; i:int; I:unsigned int;
    l:long; L:unsigned long; f:float; d:double.

Special cases (preceding decimal count indicates length):
    s:string (array of char); p: pascal string (with count byte).
Special cases (only available in native format):
    n:ssize_t; N:size_t;
    P:an integer type that is wide enough to hold a pointer.

Special case (not in native mode unless 'long long' in platform C):
    q:long long; Q:unsigned long long

Whitespace between formats is ignored.

#### byte_swap
A boolean indicates whether or not to swap adjacent bytes.  
Swap adjacent bytes of 32bits(4bytes) or 64bits(8bytes).
This is not for little-endian and big-endian swapping, and use format for that.
The option is effective when number_of_registers is ether 2(32bits) or 4(64bits), 
else it will be ignored.

### References

[1]. http://myems.io
  
[2]. http://www.modbus.org/tech.php
  
[3]. https://github.com/ljean/modbus-tk

[4]. https://docs.python.org/3/library/struct.html#format-strings