minimalmodbus | use Modbus RTU and Modbus ASCII implementation | TCP library
kandi X-RAY | minimalmodbus Summary
kandi X-RAY | minimalmodbus Summary
Easy-to-use Modbus RTU and Modbus ASCII implementation for Python.
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Top functions reviewed by kandi - BETA
- Generic generic command .
- Extract the message payload .
- Check that the inputstring is valid .
- Create the payload .
- Predict response size .
- Convert a number to a two - byte string .
- Check that the numerical value is valid .
- Convert a float value to a string .
- Parse a response payload .
- Convert a string to a float .
minimalmodbus Key Features
minimalmodbus Examples and Code Snippets
Lines of Code : 3License : Strong Copyleft (CC BY-SA 4.0)
CopyHV_A_Phase_Spannung = Hausverbrauch.read_float(0, functioncode=4, number_of_registers=2)
print(str(f'{HV_A_Phase_Spannung :.2f}')+"V -Phase A")
return _num_to_twobyte_string(register, lsb_first=True)
return _num_to_twobyte_string(register, lsb_first=False)
import minimalmodbus
def _calculate_crc_string(inputstring):
"""CalculaPin | Define
-----|-------------------------------------
1 | Power supply output +5V or +7.5V
2 | Power supply output +5V or +7.5V
3 | RS-485-B
4 | RS-485-B
5 | RS-485-A
6 | RS-485-A
7 | Ground
8 | Ground
<instrument = minimalmodbus.Instrument('COM4', 2)
instrument.write_register(0, 0xff00)
instrument.write_bit(0, 1)
print RecievedData.encode('hex')
answer = self.serial.read(number_of_bytes_to_read)[3:]
_performCommand(0x46, '0x05,0x04,0x02')
0x46 - function code
0x05 - sub function code
0x04 - baud rate 38400
0x02 - parity/stop bits 8E1
from pymodbus.client.sync import ModbusSerialClient
client = ModbusSerialClient(
method='rtu',
port='/dev/ttyUSB0',
baudrate=115200,
timeout=3,
parity='N',
stopbits=1,
bytesize=8
)
if client.connect(): # TryiLeft.write_register(4097, Ltemp)
Middle.write_register(4097, Mtemp)
Right.write_register(4097, Rtemp)
pi@rraspberrypi:~$ groups Debian-snmp
Debian-snmp : Debian-snmp
pi@raspberrypi:~ $ sudo usermod -a -G dialout Debian-snmp
Community Discussions
Trending Discussions on minimalmodbus
QUESTION
minimalmodbus does not provide a way to set multiple coils at once. I cannot find a workaround.
The modbus protocol description in the datasheet of the SMC LEC 6 controller, see link.
I try to follow the directions from the example starting at page 7 by sending the listed modbus commands using the pyton library minimalmodbus.
I want to send the command 01 0F 00 10 00 08 01 02 BE 97 but do not find a way to do this with minimalmodbus. There is not implementation of function code 15 (OF).
I reasoned as follows:
- I want to set multiple coils:
0F - Starting from position:
00 10 - I want to set 8 coils:
00 08, or one byte01 - What I want to do is set this byte to value 2 (
02), or in binary00000010
I thought this could work by setting these positions all separately:
...ANSWER
Answered 2021-Jun-22 at 12:59I was able to send the command in question by going a bit deeper in the minimal modbus class and sending the raw payload to the device:
00 10 00 08 01 02
QUESTION
I'm trying to read the values of an industry digital counter with Modbus RTU RS-485. Using USB-RS-485 conversion, and here is the master send code is taken from the following datasheet,
I am expecting that the read input register is what I'm expecting, and the API of the minimalmodbus expects to specify register number, a number of decimals, and function code.
- Does the library auto-assign the slave number, or we have to define it?
- From the datasheet, is it the register number is the address?
- And how many decimals do I expect if there's two data sequence as a response?
- Is the CRC16 check already included within the library as i shouldn't code it?
Here's my code by far, modifying examples.
...ANSWER
Answered 2021-Jun-10 at 05:34Does the library auto-assign the slave number, or we have to define it?
With MinimalModbus you pass the slave ID through in the minimalmodbus.Instrument('/dev/ttyUSB0', 1) call (the 1 is the Slave ID). How you set the slave ID on the device itself varies (this is not covered by the Modbus over serial line spec; could be a configuration program, DIP switches, based on the serial number etc. Other libraries may take different approaches (for example defaulting to Slave ID 1).
From the datasheet, is it the register number is the address?
The header in the spec tables says "No(Address)" so "10001(0000)" means register 1, address 0 (these refer to the same thing; I recommend reading the "Modbus: When 40001 Really Means 1, or 0 Really Means 1" section in this article which explains some of the issues around addressing).
And how many decimals do I expect if there's two data sequence as a response?
Not quite sure what you mean by "two data sequence". The Modbus spec only details the sending of bits (coils) and 16 bit values (input/holding registers). From a quick look at your spec it looks like this device just uses a single registers; for instance "OUT1 Output time" has "unit: ×10㎳" so take whatever is in the register and divide by 10 to get ms.
Is the CRC16 check already included within the library as i shouldn't code it?
Any decent Modbus library will look after the protocol details (such as CRC) for you (so no you don't need to code this; MinimalModbus will calculate it for you)
QUESTION
I am trying to use Python (PyCharm) to read a register on a modbus device. I have confirmed the COM port, Baud rate and other communication settings and I can use the devices application to read the value (it is a water level logger). I am getting no response from the instrument.
Register is readable in mbpoll using -
...ANSWER
Answered 2021-Jun-03 at 05:31The device manual isn't clear about the register start address, but the first register it mentions has the address of 1.
Similarly, the mbpoll command-line utility (not the one with GUI) isn't very clear about the start address. But its documentation mentions that the default value for -r parameter is 1.
I think it's safe to assume that both use the same addressing which starts from 1, as the command-line tool has no problems accessing the value.
But MinimalModbus API clearly mentions that its register start address is 0. So when using this library, you need to use registeraddress = 45 for accessing the temperature, not 46 or 40046.
But why won't 46 work? Normally, one would expect it to grab data starting from the next register and print some garbage, but not timeout. But we can't know how the device works internally. Maybe a request to access the temperature register actually triggers some measurement function and then returns a value. A request to access an unaligned data (with a wrong register value) can be simply rejected by the firmware.
If you still get timeouts with registeraddress = 45, your Python runtime may have some problems accessing the serial port. As I stated in my comment, I recommend using a logic analyzer to see what's going on on the wire. Without such a tool, you're doing blind-debugging.
QUESTION
fist Post as i normaly find the answers if i search long enough. But today is the day... I bought a EnergyMeter from Aliexpress with MODBUS RTU connection and im trying to read it out. I already tried a lot of stuff from all over the Internet.
This is the Datasheet of the EnergyMeter1
I tried pyModbus and minimalmodbus.
My both Scripts:
...ANSWER
Answered 2021-May-14 at 13:08Thanks to @Brits i got it running.
I had to use read_float(0, functioncode=4, number_of_registers=2) where 0 is decimal.
If i want to read 001A i had to convert from hex to dec = 26.
Works very good
QUESTION
I am trying communicate via Modbus protocol to a uC2 SE controller for a air-water chiller. A serial RS485 to USB port COM is connected with the controller and I was able to read registers, but it is not possible to change their values by using write_register function. I have also tried with tester. exe and Modscan64 softwares and the result was the same, they only can read but not write. I have introduced here the piece of code is being run and debug responses can be checked. Thank you for your help in advance!
Change temperature setpointCOOLING_SETPOINT_REG = 41
try: print(instrument.read_register(COOLING_SETPOINT_REG,1)) except IOError: print('Failed to read from instrument')
NEW_TEMPERATURE = 20.1
return_flag = instrument.write_register(COOLING_SETPOINT_REG, NEW_TEMPERATURE,1,functioncode = 6, signed = True) # Registernumber, value, number of decimals for storage output_flag = 'SUCCESS' if return_flag else 'FAILURE' print('writing single register status ' + output_flag + '\n' )
try: print(instrument.read_register(COOLING_SETPOINT_REG,1)) except IOError: print('Failed to read from instrument')Respuesta debug:
MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): '\x01\x03\x00)\x00\x01UÂ' (01 03 00 29 00 01 55 C2) MinimalModbus debug mode. Opening port COM8 MinimalModbus debug mode. Clearing serial buffers for port COM8 MinimalModbus debug mode. No sleep required before write. Time since previous read: 334030.00 ms, minimum silent period: 4.01 ms. MinimalModbus debug mode. Closing port COM8 MinimalModbus debug mode. Response from instrument: '\x01\x03\x02\x00ȹÒ' (01 03 02 00 C8 B9 D2) (7 bytes), roundtrip time: 62.0 ms. Timeout for reading: 1000.0 ms.
20.0 MinimalModbus debug mode. Will write to instrument (expecting 8 bytes back): '\x01\x06\x00)\x00É\x98T' (01 06 00 29 00 C9 98 54) MinimalModbus debug mode. Opening port COM8 MinimalModbus debug mode. Clearing serial buffers for port COM8 MinimalModbus debug mode. No sleep required before write. Time since previous read: 47.00 ms, minimum silent period: 4.01 ms. MinimalModbus debug mode. Closing port COM8 MinimalModbus debug mode. Response from instrument: '\x01\x06\x00)\x00É\x98T' (01 06 00 29 00 C9 98 54) (8 bytes), roundtrip time: 47.0 ms. Timeout for reading: 1000.0 ms.
writing single register status FAILURE
MinimalModbus debug mode. Will write to instrument (expecting 7 bytes back): '\x01\x03\x00)\x00\x01UÂ' (01 03 00 29 00 01 55 C2) MinimalModbus debug mode. Opening port COM8 MinimalModbus debug mode. Clearing serial buffers for port COM8 MinimalModbus debug mode. No sleep required before write. Time since previous read: 46.00 ms, minimum silent period: 4.01 ms. MinimalModbus debug mode. Closing port COM8 MinimalModbus debug mode. Response from instrument: '\x01\x03\x02\x00ȹÒ' (01 03 02 00 C8 B9 D2) (7 bytes), roundtrip time: 47.0 ms. Timeout for reading: 1000.0 ms.
...ANSWER
Answered 2021-Mar-22 at 15:06Writing is successful.
write_register from minimalmodbus has "None" return value.
So checking the return_flag results in failure.
QUESTION
I need to write and read registers from a serial device. Everything works fine, but I need to store the messages in a variable. For example:
...ANSWER
Answered 2021-May-05 at 19:56Option 1) Modify the library to return the "answer" variable from private function _communicate to your program.
Option 2) Save the debug log output to a variable and filter this variable for the string.
QUESTION
I am currently working on a project of data acquisition with a RaspberryPi. When i launch my request script, sometimes (rare but too often) my slave (computer) detects a CRC error or invalid length. I'm guessing the error could come from the fact that, as my script is fast and asks for hundreds of register in a few seconds, sometimes the message is incomplete and my slaves detects it as a wrong message. I wanted to know if it was possible that minimalmodbus isn't timed right and sometimes will send a wrong or part of a request (incomplete).
Error returned on the slave:
...ANSWER
Answered 2021-Apr-04 at 10:04Sounds like your problem could be the byte order used by the emulated slave.
QUESTION
I'm using this USB-to-RJ45 cable to connect my Windows 10 developer workstation to the EPEver Tracer 3210an solar charge controller.
I'm using Python 3.8.6 with the minimalmodbus module to attempt to connect to the device, retrieve data, and control the device parameters.
The charge controller returns the input voltage of the photovoltaic (PV) panels.
Actual Result ...ANSWER
Answered 2020-Oct-08 at 19:16Communication with these controllers (manual) is via RS485 (delivered through an RJ45 connector). This is only mentioned briefly in the manual ("RS485 interface" in the technical specifications section).
The cable you are using appears to be a router console cable which, I believe, uses the RS232 protocol (see document from Cisco as an example). RS232 and RS485 are different, and incompatible, so this cable will not work.
The manual for this controller does not go into much detail and I could not see a modbus manual on the EPEVER website. I use Tracer-BN series units and epever support emailed me a manual detailing the modbus setup; as your unit also supports the MT50 remote meter I'm assuming its registers are the same. You can probably find the manual by searching for "common software or MT50 LCD unit" (with the quotes) - I believe version 2.5 is the latest (note: I'm not posting the link because it does not seem to be available on the official website so click at your own risk!)
The RJ45 wiring (from the above manual) is:
QUESTION
I have made a PCB circuit that has a microcontroller (Microchip PIC18F47K40) that can program a parallel flash memory (Microchip SST39SF040).
The microcontroller communicates to my PC (Windows 10) via Modbus RTU over a USB to UART adaptor.
I use five Modbus registers...
Control, Address0, Address1, Address2, Data
Control = read, write, erase
Address0,1,2 = Address bus
Data = Data bus
Using Baseblock program I have verified the microcontroller is working fine, and in Python I can send individual commands ok.
My goal is to be able to read in a binary file and send to the microcontroller to program the flash memory chip.
This is the code I have so far: -
...ANSWER
Answered 2020-Jun-08 at 18:23You can use int(dataByte.hex())
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Install minimalmodbus
You can use minimalmodbus like any standard Python library. You will need to make sure that you have a development environment consisting of a Python distribution including header files, a compiler, pip, and git installed. Make sure that your pip, setuptools, and wheel are up to date. When using pip it is generally recommended to install packages in a virtual environment to avoid changes to the system.
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