Cannot run example code (RTU Slave)

[MGabeler]

Description

Hi,

I installed this library on my RP Pi Pico (H), micropython. I get an syntax error running the example code from the library (Slave RTU). The error exists in the serial.py sub code of the library line 2 of the example code : from umodbus.serial import ModbusRTU(Modbus). When I run serial.py I got an error about the costum packages. Do I miss any extra necessary libraries that are used next to the Micropython-modbus library? I did read other questions about running this library on a RP Pi Pico but it didn't answer my question / I didn't help me fix this problem.

Reproduction steps

This is the error I got when running the example code Slave RTU.

Traceback (most recent call last): File "", line 2 SyntaxError: invalid syntax

this is the code I'm running:

from machine import Pin from umodbus.serial import ModbusRTU(Modbus)

rtu_pins = (Pin(0), Pin(1)) # (TX, RX) uart_id = 0

slave_addr = 1 # address on bus as client

client = ModbusRTU( addr=slave_addr, # address on bus pins=rtu_pins, # given as tuple (TX, RX) baudrate=9600, # optional, default 9600 data_bits=8, # optional, default 8 stop_bits=1, # optional, default 1 parity=None, # optional, default None ctrl_pin=18, # optional, control DE/RE uart_id=uart_id # optional, default 1, see port specific documentation )

register_definitions = { "COILS": { "EXAMPLE_COIL": { "register": 123, "len": 1, "val": 1 } }, "HREGS": { "EXAMPLE_HREG": { "register": 93, "len": 1, "val": 19 } }, "ISTS": { "EXAMPLE_ISTS": { "register": 67, "len": 1, "val": 0 } }, "IREGS": { "EXAMPLE_IREG": { "register": 10, "len": 1, "val": 60001

}

}}

MicroPython version

v.1.19.1

MicroPython board

Raspberry Pico

Relevant log output

No response

User code

No response

Additional informations

No response

[beyonlo]

Hello @MGabeler

I installed this library on my RP Pi Pico (H), micropython. I get an syntax error running the example code from the library (Slave RTU).

I believe that you are talking about this tcp_client_example.py right?

The error exists in the serial.py sub code of the library line 2 of the example code : from umodbus.serial import ModbusRTU(Modbus).

Look that (conforming tcp_client_example.py), line 20, the correct is import modbus client classes is from umodbus.tcp import ModbusTCP. You are using from umodbus.serial import ModbusRTU(Modbus) Maybe this can be the problem.

A important aditional information to paste here is: what ModBus version of this library that you are using:

from umodbus import version
print('Used micropthon-modbus version: {}'.format(version.__version__))

Another very useful information, if you can, is to paste the real output running on terminal.

[MGabeler]

I have this library: Used micropthon-modbus version: 2.3.3 I use Modbus RTU with Tx and Rx on 0 and 1 to a max485 module to convert to RS485. wait, now it works, I just found the error. instead of using: from umodbus.serial import ModbusRTU(Modbus) you need to use this: from umodbus.serial import ModbusRTU Now I'm going to set the Pi 4 B as a master. that's the next step. I have no errors on the slave code right now. so will be back when the master doesn't work xD Can I better use Python instead of micropython for the master? (Pi 4B) and thnx for the fast response :)

[beyonlo]

wait, now it works, I just found the error. instead of using: from umodbus.serial import ModbusRTU(Modbus) you need to use this: from umodbus.serial import ModbusRTU

Yes, that was exactly what I wrote for you above!

Now I'm going to set the Pi 4 B as a master. that's the next step. I have no errors on the slave code right now. so will be back when the master doesn't work xD Can I better use Python instead of micropython for the master?

This ModBus library works on MicroPython, and there is a MicroPython version for Unix that run on Linux (including ARM arch). The Pi 4 B is ARM, so you can install tha MicroPython on PI4 (running linux) too. So, my suggestion is you just install MicroPython on the PI4, and use the ModBus Master of this Lib!

thnx for the fast response :)

No problem, you are wellcome!

[brainelectronics]

Hi @MGabeler is your issue solved with the help of @beyonlo answer? If so, could you close this issue? :)

[MGabeler]

Hi, that would indeed solve my problem i suppose, but unfortunately i cant find how to install micropython on a raspi 4. I can not find a raspi 4 version on micropython.org

[beyonlo]

Hello @MGabeler

Hi, that would indeed solve my problem i suppose, but unfortunately i cant find how to install micropython on a raspi 4. I can not find a raspi 4 version on micropython.org

There is no ready to go MicroPython binary to download and use on RP4, but, logged in your RP4 (with Linux), you can just to download the Micropython source code and compile by your self. That url above that I pasted for you has the complete instructions to compile, including dependencies.

[brainelectronics]

If you really want to use MicroPython on a Linux (Raspberry) you could go with a Docker solution. I use this to test this lib in the CI Chain. Further details are explained in the MicroPython Modbus testing chapter

[brainelectronics]

@MGabeler I'll close this issue for now. In case you face some other issue please open a new issue