Modbus Gateway

[jeroenst]

I have several devices that use modbus via rs485 connected with an esp8266 with own firmware.

Is it possible to create an mqtt to modbus gateway using tasmota?

In this case all devices that use modbus can be directly controlled and read via a domotica platform like Nodered.

I think this is just a minor implementation, receive commands via mqtt and parse them to the modbus device and send the parsed response back to mqtt.

I can make a small standalone example code/function but tasmota is to complex for me to implement this.

If someone could help it wouldn't take too much effort I think and will add a great extension of functionality for tasmota.

[barbudor]

Wouldn't this already work by using SerialBridge ?
If no parsing is made on Tasmota
Send SerialSend send command through MQTT
And process SerialReceive message from MQTT

[jeroenst]

That would indeed work, but in that case it will be raw data that has to be parsed in Nodered.

It would be nice to have commands like

ReadInputRegister Address Type Register

With a reply of the value.

Same for ReadDiscreteInputRegister ReadCoilRegister and ReadHoldingRegister.

For writing it would be useful to have

WriteHoldingRegister Address Type Value

Type is default 8 bits MSB integer (8MI) but can be 8, 16 or 32 bit MSB/LSB integer or float.

[barbudor]

So it would need a specific ModbusGateway driver
Could be native C++ if you want it for both ESP8266 and ESP32
Or in Berry for only ESP32

[pkkrusty]

I vote for both and chip in $20 for cup of coffee for the developer.

[jeroenst]

I vote for ESP8266 and chip in $10 for a beer for the developer.

[jeroenst]

Esp8266 would be mandatory for my projects.

I can create an example cpp file with 2 functions for c++ in Arduino ide which may be ported to tasmota if preferred.

[laurentppol]

I think You have same problem as me:

• is there ANY "Developer Guide" for Tasmota?
  Describing it's internals, data flows etc.
  I know (as a developer too, but on AVR) that writing docs is worst that a programmer may be faced to.
  But forcing some (programmer too) to understand whole Tasmota (as it became big) is a problem too.

From my experience: tried to add driver for ORNO OR-WE-504 single phase energy meter by (for start) stripping code for
WE-517, but there I find not docsss on whaat may I expect from which module (ex serial, ex WWW, MQTT etc).
And how to debug serial (at Tasmota level), as I set up data for "query" OR-WE but see no data (or not correct) on HW.

[barbudor]

As I already told you @laurentppol , did you read https://tasmota.github.io/docs/For-Developers/ ?
The the code is the doc which provides a lot of examples of how to write drivers for various categories such as sensors, energy meters, ...
And you can still ask questions
And if you feel docs is not enough, you are welcomed to improve it

[laurentppol]

@barbudor OK, THX (again?), will read before asking. :)

[laurentppol]

https://tasmota.github.io/docs/For-Developers/ ?

Have read. Still don't see any "central point" with (possibly) a diagram of how Tasmota is organised.
What is the "core", what services it provides, what it requires from user written modules, some starting point to read Tasmota code.

[barbudor]

@jeroenst
I don't have any ModBus device and experience in ModBus in general but quite some experience in various Tasmota drivers, energy or sensors
If you know of any debug tool or device simulator that could be used, and if we agree on a spec, I can help

[RichieB2B]

Tasmota also support MQTT out of the box: https://github.com/arendst/Tasmota/blob/development/tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino

All you need to do is to tie them together in a flexible, easy configurable way.

[jeroenst]

I use tasmota with mqtt in several projects.

When I have time I will dive into this.

[RichieB2B]

Is your idea to be able to configure the Modbus device address, function code and start address at compile time or runtime? If you are considering runtime take a look at https://tasmota.github.io/docs/Smart-Meter-Interface/ and https://github.com/arendst/Tasmota/blob/development/tasmota/tasmota_xsns_sensor/xsns_53_sml.ino which also has this approach. Their MQTT output looks pretty flexible as well. Converting xsns_53_sml.ino to a more generic Modbus sensor would be very useful.

I would be fine with defining Modbus device address, function code and start addresses at compile time. That makes writing the sensor a lot easier.

[jeroenst]

At runtime, so multiple different modbus devices can be connected.

A command in that case could be:

ModbusRead {"deviceaddress": <deviceAddr>, "register" : (Input|Holding|Coil|Discrete),  "address" : <address>, "length": <length>, "endian" : (MSB|LSB), "type" : (FLOAT|INT|UINT)}

The response in that case would be:

tele/xxxx/RESULT { "ModbusRequest" : { "deviceAddr": <deviceAddr>, "register": <Register>, "address": <address>, "value": <value> }

For writing registeres something similar would be fine I think.

I created a first start of a modbus bridge driver based on the serial bridge driver. I can select the TX and RX pin in the Tasmota menu, but the commands like ModbusRequest are Unknown. How do I fix this?

https://github.com/jeroenst/Tasmota/tree/ModBusBridge

[jeroenst]

I have working code at this moment for reading registers. In the following day's I will implement writing registers. After that I will create a pull request for review. Any comments are already welcome.

https://github.com/jeroenst/Tasmota/tree/ModBusBridge

[laurentppol]

@gemu2015 Here is doc I got from Polish representative.
OR-WE-504 RS485-modbus communication protocol.pdf
register OR-WE-504.xlsx

[gemu2015]

it seems to be msb first. so this script should be ok.

[TheChatty]

Thanks for implementing this ModBus bridge. I have a few uses for ModBus in Tasmota myself. And MQTT2ModBus is one of them. Currently I use SML for that (at least for predefined reading).

Can this solution be used to expose read values in the same manner (like display readings on WebUI and broadcast via MQTT)?

Also I'd appreciate if I could use Tasmota as TCP2ModBus bridge concurrently (e.g. no reconfiguration).

[jeroenst]

See https://github.com/tasmota/docs/blob/development/docs/Modbus-Bridge.md for documentation.

There is no tcpmodbus gateway like serial tcp gateway unfortunately. But you can send commands by console or mqtt in order te read modbus slaves.

[TheChatty]

My last paragraph was a suggestion for implementation. My linked issue contains information about what is necessary to convert between TCP and RTU modbus protocol (very little, actually). I was hoping you could have a look into it and maybe borrow a few lines from TCP bridge and 'just' insert the few protocol conversion steps.

[jeroenst]

I want to give it a try but I need to know from @arendst if I can expand the current modbusbridge code or if I have to add a separate modbustcpbridge. Eitherway I think it should have it's own define.

[jeroenst]

@TheChatty Are you able to test the code when I commit it to my github repository in the following days?

[arendst]

Pls expand the current driver

[TheChatty]

@jeroenst: Yes, indeed (no problem in compiling your branch myself). I have a modbus slave (a Trovis heating regulator) of which the vendor offers a Windows tool suite which either communicates via serial RTU and a USB TTL adapter or via TCP and it's according slightly modified (wrapped) protocol.

I had this working via a local running Python TCP to serial RTU gateway. Having this integrated into Tasmota would be fabulous. Especially if it works concurrently:

• normal use case: Tasmota reads continuously certain parameters and publishes them to its WebUI and to MQTT (log vessel temp etc.). Also it responds to specific MQTT read quests (your use case)
• special use case: Windows tool suite connects via TCP for certain configuration activities, which would block normal use case temporarily.

This (German) thread alone is home to many ppl seeking this feature.

[jeroenst]

I pushed test code to my repo ( https://github.com/jeroenst/Tasmota/tree/ModbusTCP ) I also did some tests with these php scripts and it seems to work ok:

modbustcp.php

<?php
    $fp = fsockopen("172.30.31.176", 8000, $errno, $errstr, 30);
    if (!$fp) {
        echo "$errstr ($errno)<br />\n";
    } 
    else 
    {
        fwrite($fp, chr(00) . chr(01) . chr(00) . chr(00) . chr(00) . chr(06) . chr(1) .  chr(3) . chr(00) . chr(01) . chr(00) . chr(4));
        while(!feof($fp))
        {
            $str = fread($fp, 1);
            if ($str) printf ("%d,", ord($str[0])); // If you expect an answer
        }
    fclose($fp); // To close the connection
}
?>

replymodbusrtu.php

#!/bin/php
<?PHP
	// Calculate CRC16 (ModBus)
	function crc16($string)
	{
          $crc = 0xFFFF;
          for ($x = 0, $xMax = \strlen($string); $x < $xMax; $x++) {
              $crc ^= \ord($string[$x]);
              for ($y = 0; $y < 8; $y++) {
                  if (($crc & 0x0001) === 0x0001) {
                      $crc = (($crc >> 1) ^ 0xA001);
                  } else {
                      $crc >>= 1;
                  }
              }
          }
          $crchigh = $crc & 0xFF;
          $crclow = $crc >> 8;
          return \chr($crc & 0xFF) . \chr($crc >> 8);
	}
	


// 11 03 06 AE41 5652 4340 49AD
$fd = dio_open('/dev/ttyUSB0', O_RDWR | O_NOCTTY | O_NONBLOCK);
dio_fcntl($fd, F_SETFL, O_SYNC);

dio_tcsetattr($fd, array(
  'baud' => 9600,
  'bits' => 8,
  'stop'  => 1,
  'parity' => 1
)); 

$data = chr(1) . chr(3) . chr(8) . chr(255) . chr(2) . chr(254) . chr(4)  . chr(255) . chr(0). chr(255) . chr(1);
$data .= crc16($data);
for ($i = 0; $i < strlen($data); $i++)
{
  printf ("%d ", ord($data[$i]));
  dio_write($fd,$data[$i],1); 
}

?>

[jeroenst]

Tasmota Modbus Bridge won't query the modbus devices by it self, this has to be done via mqtt, http or now also tcp

[jeroenst]

This feature is now available in the development Branche.

I encourage users to test this feature so bugs can be found and solved.

[timaseth]

I am afraid, I could not make it work.
Here are my process steps using Tas Dev 12.0.2.4

1. Compiled using

#define USE_MODBUS_BRIDGE                        // Add support for software Modbus Bridge (+3k code)
#define USE_MODBUS_BRIDGE_TCP                    // Add support for software Modbus TCP Bridge (Also enable Modbus Bridge!) (? code)

Compiled without any errors.

2. Set TX and RX pins as prescribed
   

3. Modbus device is a known good device working well with Tasmota Smart Meter Setup.

> 12:51:35.067 CMD: ModbusSetBaudRate
> 12:51:35.072 RSL: RESULT = {"Command":"Unknown"}
> 12:51:41.395 CMD: modbussend {"deviceaddress": 1, "functioncode": 3, "startaddress": 1, "type":"uint16", "count":4}
> 12:51:41.400 RSL: RESULT = {"Command":"Unknown"} 

Tx light does flash on the Modbus UART adapter.

[jeroenst]

Use ModbusBaudrate instead of ModbusSetBaudRate, see if that command works.

[timaseth]

No luck!

> 14:04:51.351 CMD: ModbusBaudrate
> 14:04:51.357 RSL: RESULT = {"Command":"Unknown"}
> 14:05:03.028 CMD: ModbusBaudrate
> 14:05:03.034 RSL: RESULT = {"Command":"Unknown"}

The Send command don't work either

[jeroenst]

You must specify ModRX and ModTX in module configuration, not in the template. Or select Generic (0) in module configuration if you wish to use the template.

[jeroenst]

Did you try to change pins in device configuration?

Me and @TheChatty both use this firmware and do not experience your issue.

[timaseth]

Pins right or wrong, attached modbus device params right or wrong should not return an unknown command result, me thinks.
Can you make a step by step process for me please - perhaps will help others too!
Thanks!

[jeroenst]

Use a fresh erased and tasmota flashed esp8266 device.

Goto configuration
Goto configure module
Set module type to generic 18
Save configuration

Goto configuration
Goto configure module
Set Rx Gpio3 to ModRX
Set Tx Gpio1 to ModTx
Save configuration

[timaseth]

I retried on 3 different devkits but could not make it work. Guess I'll wait and see if others can make it work once there is a public release.
Thanks for your work and efforts nevertheless!
PS: I have so many Tas (100+) and Modbus (10+) devices, I was eager to get this going.

[jeroenst]

I retried on 3 different devkits but could not make it work. Guess I'll wait and see if others can make it work once there is a public release. Thanks for your work and efforts nevertheless! PS: I have so many Tas (100+) and Modbus (10+) devices, I was eager to get this going.

I found the bug which caused Tasmota to crash when modbusbridge was configured for the first time. I never experienced this bug because it only happens on a device which was never configured for modbus bridge before. In the first releases this bug was not happening because modbusbridge wasn't started at boot in the past.

See: #9586 (comment)

I hope this helps you out.

[Pietjuhbel]

Hello guys,
perhaps I could also chip in on the fun. I was already looking for a solution as mentioned in this topic.

I've got two identical Growat inverters, so far I have hooked on up to a ESP32 with TTL converter and flashed the dev branch tasmota.
I can confirm the modbus bridge is functioning up to the point that I can read/set baudrate, also the send command returns ok.

Coding is not new to me, but I've got next to no experience in tasmota / berry coding so I would really appreciate a bit more verbose explanation so I could learn a thing or two.

So what's next, could you maybe advice how to query modbus devices from the tasmota commandline for starters?
Hope to be of some assistance for all.

[Pietjuhbel]

@jeroenst Serial config was wrong, I can confirm the driver appears to be working properly.

Next to figure out how to handle the data in a way that it can be sent through MQTT to Domoticz

[jeroenst]

Great to hear it is working!

[dennis77777]

I am having the same problem

, how would I know if my serial port is configured correctly?

[TheChatty]

Try ModBusSerialConfig 3

[dennis77777]

still the same result. What does that command do? I don't see it in the documentation.

[Pietjuhbel]

@jeroenst could you perhaps give me some pointers on how to use the modbus bridge in berry?
My idea is to have a script in berry that runs periodically , queries the modbus devices and publishes to mqtt, my experience in the berry language however is to limited to even get started.
Thanks in advance!

[darrylb123]

Neither pullup, or pulldown works. The RPS has an LED and it flashes when the data is sent. I just think there is some kind of timing issue that causes the RTS to be pulled low before the data has been sent, even though it has a flush() before going low which I assume is synchronous. Either that, or the RTS is not high long enough before the data is sent. If the same GPIO line is configured as a relay, it works every time.

…

On Fri, Jun 16, 2023 at 3:30 PM JeroenSt ***@***.***> wrote: I can confirm that module works fine but modules with a tx enable line also work fine (normally). — Reply to this email directly, view it on GitHub <#15703 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABTSUVNDFYJCHA5F4LJVLWLXLPVQNANCNFSM5XD34LXQ> . You are receiving this because you commented.Message ID: ***@***.***>

[jeroenst]

It looks specific to your rs485 board.

Is it possible the rts of your rs485 chip is inverted?

You can try to change high and low in the code or add some delays.

[darrylb123]

No it's not inverted. Relay on enables transmit, led is on solid. The led flashes on when using Tx enable. I'll need to get set up to compile tasmota, I've not done it before. I'll add some delays in the code next week, busy on the weekend.

…

On Fri, 16 Jun 2023, 5:38 pm JeroenSt, ***@***.***> wrote: Is it possible the rts of your rs485 chip is inverted? You can try to change high and low in the code or add some delays. — Reply to this email directly, view it on GitHub <#15703 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABTSUVOLFJFZ5LY6IZCUWYTXLQEPFANCNFSM5XD34LXQ> . You are receiving this because you commented.Message ID: ***@***.***>

[darrylb123]

I set up my machine to compile tasmota and cloned the latest repository. That version (12.5.0.4) works correctly without any changes. I downloaded and re-installed 12.5 and that worked correctly too. I can't explain, I changed nothing in the hardware since testing with setting the gpio as a relay.

…

On Fri, Jun 16, 2023 at 5:52 PM Darryl Bond ***@***.***> wrote: No it's not inverted. Relay on enables transmit, led is on solid. The led flashes on when using Tx enable. I'll need to get set up to compile tasmota, I've not done it before. I'll add some delays in the code next week, busy on the weekend. On Fri, 16 Jun 2023, 5:38 pm JeroenSt, ***@***.***> wrote: > Is it possible the rts of your rs485 chip is inverted? > > You can try to change high and low in the code or add some delays. > > — > Reply to this email directly, view it on GitHub > <#15703 (reply in thread)>, > or unsubscribe > <https://github.com/notifications/unsubscribe-auth/ABTSUVOLFJFZ5LY6IZCUWYTXLQEPFANCNFSM5XD34LXQ> > . > You are receiving this because you commented.Message ID: > ***@***.***> >

[Yocee84]

Hi!

i cant use the ModbusSerialConfig:
06:34:37.822 CMD: ModbusSerialConfig 0
06:34:37.835 MQT: stat/tasmota_71B690/RESULT = {"Command":"Unknown"}

whats wrong?

[Yocee84]

Oh, thx. its fine.

But. I set baudrate to 4800, and config to 8o2

but i saw this:
"StatusPRM": {
"Baudrate": 115200,
"SerialConfig": "8N1",
"GroupTopic": "tasmotas",
"OtaUrl": "http://ota.tasmota.com/tasmota32/release/tasmota32.bin",
"RestartReason": "Software reset CPU",
"Uptime": "0T00:00:06",
"StartupUTC": "2023-06-21T06:49:14",
"Sleep": 50,
"CfgHolder": 4617,

And nothing communication with thermosthat. ( With usb modbus adapter, and elfin ew11 it is working.)

[jeroenst]

I don't know where that error comes from.

Which rs485 adapter are you using?

[Yocee84]

Hi!

I use this module:
https://www.aliexpress.com/item/1005001621746811.html?spm=a2g0o.order_detail.order_detail_item.9.4a61f19cMjscV2

[zizebra]

I have been pulling my hair on this too. i think i have misunderstood some of the instructions. I am trying to communicate with a SunSynk inverter. I have set TX and RX pin as the ModBR TX and ModBR RX, then I set Pin4 as ModBR Ena. However, when I send the command below, the esp32 device always responds with Done. but no response from the inverter.
ModBusSend {"deviceaddress": 1, "functioncode": 3, "startaddress": 1, "type":"raw", "count":4}.

Iam using Max 485 TTL adapter.
My second question is on using the ModbusTCPStart and the two other commands. These always return unknown command. What is required for these to work? I thought they should be available once I have configured the 3 ModBR pins.

[jeroenst]

Done means sending the modus packet has been done. The received message will be in a separate message. Modbustcpstart needs an extra define in order to work. Did you check ModbusSerialConfig?

Also check documentation with examples.

[zizebra]

Modbustcpstart needs an extra define in order to work.

i take it this Recompile.modbusserialconfig is set to 3 for 8n1, baudrate is set to 9600

[zizebra]

it turns out in my case that i required a level shifter between my esp32 and RS485 TTL device. I cannow get responses. Now i need to learn how to translate the responses into human readable format.

[utya]

I've been struggling with modbus for almost a week now. I cannot understand what is the problem. I use the xy-107 module and connected it to wemos d32 mini, vcc-3.3, tx-gpio1, rx-gpio3. and I don’t get a response from the device, maybe the tx and rx lines need to be pullup?

[jeroenst]

Maybe check the baudrate?
Also measuring the rx and tx with an oscilloscope could help.
I can only say it works fine at several locations currently.

[utya]

I thought it might not be possible to connect to the gpio1 / gpio3 pins

[sfromis]

A general advice is to try swapping tx/rx. Sometimes they are labeled "from the outside", instead of what they connect to.

[jeroenst]

Gpio 1 and 3 will work fine normally

[utya]

A general advice is to try swapping tx/rx. Sometimes they are labeled "from the outside", instead of what they connect to.

yes, tried, no changes

[zizebra]

yes its using that 8n1. I will try the software serial and check out what i get

[jeroenst]

You can give it a try but I think software serial will make it worse.

[jeroenst]

Maybe you can try to read one complete different register like voltage and see how it responds.

[zizebra]

After a long investigation, I eventually found that the response were not coming from my inverter, they seemed to be commands being mirrored back on the rx pin. After disconnecting the inverter and sending a command, I noted that I was still getting a response. I removed the logic converter, and no more responses were coming. I am now trying to determine the response received to see if they make sense .

[jeroenst]

Maybe your logic converter is faulty?

[Aida3000]

Hi,

I suspect an error in Tasmotas 13.1.0: I compiled SML, scripts and rules into my Tasmota. It is connected via a RS485-converter with a ESP8266 (but I tried also Tasmota 12.4 and ESP32). My script for the smart meter SMD72D-M goes like that:

D
B
->sensor53 r
M 1
+1,14,m,0,9600,SDM72D,12,1,01040000
1,010404ffffffff@i0:1,Voltage P1,V,voltage_phase1,2

And here is the dump of sensor53:

09:26:37.500 > 01 04 00 00 00 02 71 cb
09:26:37.555 : fe 01 04 04 43 64 8f d4 cb b0
09:26:37.606 > 01 04 00 00 00 02 71 cb
09:26:37.661 : fe 01 04 04 43 64 8f d4 cb b0
09:26:37.712 > 01 04 00 00 00 02 71 cb
09:26:37.766 : fe 01 04 04 43 64 8f d4 cb b0

You see, the demanded voltage (01040000) leads to "43 64 8f d4", the voltage of 228.49995. So Tasmota receives the data, doesn't it?

The problem is that it displays a voltage of 0.00 at the front page. The mqtt-data is the same:
tele/tasmota_022F0C/SENSOR = {"Time":"2023-08-23T09:24:44","SDM72D":{"voltage_phase1":0.00}}.

I know, that Tasmota can handle everything, because I used a Tasmota-Sensor-bin with SDM630-Pins RX/TX set in "configure module". They produce some data. Unfortunately not the special data I 'm looking for.

Any hint in some direction would be appreciated very much. I tried everything I can think of, an error in Tasmota seems the only explanation for me.

Michael

[gemu2015]

this is an hardware error. replace you RS485 converter.
response should NOT start with 0xfe!
this means that the bidirectional converter is faulty and thus emits and extra char.

Should look like this:

09:26:37.500 > 01 04 00 00 00 02 71 cb
09:26:37.555 : 01 04 04 43 64 8f d4 cb b0

[Aida3000]

Thank you for your hint. But I guess it's not it:
I tried a different one with same result.
And: Using the same converter works on Tasmota Sensors.

But: Is there a way to let Tasmota ignore the first byte - because the rest is ok?
And: Is there a way to display the Console of the Sensor-Version? sensor53 d1 doesn't work.

[Aida3000]

After a long research in the cellar I turned to the forums and voila: the problem is known and already solved. It has to do with the CRC-check.
See esphome/issues#3912 and https://espeasy.readthedocs.io/en/latest/Plugin/P078.html. EspEasy has solved it.
I use now the Build: ESP_Easy_mega_20230822_energy_ESP32solo1_4M316k Aug 22 2023 and it works. Its the only EspEasy instalce here since I prefer Tasmota.

[gemu2015]

i have several modbus devices in use e.g. SDM630, SDM530, GROWATT
they work without any problems.

your descriptor has a fatal problem, the serial interval is set to 1 which means 100ms. this is much too short for these meters.

+1,14,m,0,9600,SDM72D,12,1,01040000

try

+1,14,m,0,9600,SDM72D,12,10,01040000

this is 1 second to be sure, but you may try lower values up to 300 ms

you must get rid of the trailing 0xfe

[Aida3000]

Set it up with the delayes you wrote. Unfortunately with no effect. The same "FE" start like before.
For me it is evident: the problem is resolved with espeasy and they point to the crc. Seems I should stay with that solution.

[RaW79]

Hi
Thanks for your great initiative and work in making this Modbus bridge happen.
Kindly ask for your hints regarding my setup (ESP32 S2 Tasmota 13.3.0) and I´m struggeling transfering Modbus data at all.
In my test setup this is from modbus tcp simulator to mqtt.
With the tasmota log I´m missing the result of "returned date" as shown in the docu.
{"ModbusReceived":{"DeviceAddress":<value>,"FunctionCode":<value>,"StartAddress":<value>,"Length":<value>,"Count":<value>,"Values":[value1,value2,value3,valueN]}}

I´m only getting back:
08:07:08.073 RSL: RESULT = {"ModbusSend":"Done"}
This is happening in both ways, acting as client from:

or as Master from

Thx!

[jeroenst]

That's true, you can create a rule for it to start at init

[RaW79]

May I ask for a hint how to use this command in a rule?

tried several options like:

Rule1
ON System#Boot DO ModbusTCPStart 502 ENDON
Rule1 1

But this does not work. Thanks

[barbudor]

System#boot is likely too early
Try Wifi#connected

[RaW79]

Thanks. Works

[sfromis]

Actually, Wifi#connected is before System#boot, which is after both Wifi and MQTT connections are up. Of course, if it cannot connect to MQTT, you may get no System#boot.

[ctc]

Attention:
ESP32 using USB Module Uart0 (standard rx/tx pins) sometimes does not work (no receive) as some modules have no resistor between USB Uart and ESP32 rx.
Switching to Uart1 at another ports helps.

[Sangito-hack]

Hello community,
I got a lot of issues and figure it out something.
I try to make work the "MODBUS_BRIDGE_TCP" by compiling the source of the define uncommon.
#define USE_MODBUS_BRIDGE // Add support for software Modbus Bridge (+4.5k code)
#define USE_MODBUS_BRIDGE_TCP // Add support for software Modbus TCP Bridge (also enable Modbus TCP Bridge) (+2k code)
Nothing seems to work, the Modbus command send me errors and look like the Modbus Bridge wasn't event compile, just like timaseth.
When I read this blog, I found the post of djconcept that work without any issue and the guy put the version of tasmota he uses... (thank you man)
I switch from actual official "V13.4.0" to the version of djconcept "V12.3.1" and bam, everything works flawlessly.
It looks like the support of Modbus broke somewhere between these two versions of tasmota.
My next try would be to find on which version Modbus support broke and why it happens.
Stay tune...

[Sangito-hack]

The bin provides on the web site work great for the Modbus RTU to MQTT, but the compiled programme I do on my computer, broke this featuring.
Any compiling broke the Modbus function. That is why I was so surprised version v12.3.1 work without any issue. Let me do more tests and I will come back with the version where it changes.

[Sangito-hack]

I got a lot of issue to figures it out what to do to make it work but seems no v13 seem to work on my computer, but the v12 work like a charm.
I'm still wondering what the command ModbusTCPConnect is for .

[jeroenst]

Afaik Modbustcpstart starts a server on listening port and modbustcpconnect connects to a remote server. Protocol is the same.

[Sangito-hack]

I understand that, but i what the utility of a remote connect for a esp if nothing can be send front the RTU to the TCP side of the modbus protocole?
I never see a master waiting for a remote connection to send modbus trame. Usualy slave do that, but esp can handle no master resquest from is rtu side...
From my observation even the master request from the master from the tcp side is nowhere to be seen in the mqtt side or the console, only the responce from the rtu is handle by mqtt and the console...

[Halbamy]

I have the same Problem with 13.4.0.
Modbus commands over mqtt are fine. But I can't get the TCP bridge to work.

[RaW79]

Hello community,

now I purchased a TTL RS485 converter this model:

and tried to learn how to use the ModbusBridge of Tasmota. I used ESP32 S2 Mini (purple Board) and configured GPIO 3 as ModBr RX and GPIO 5 as ModBr TX.

According testing in the console the ModBr seems to be active and in case of sending there is also a red LED blinking at the TTL converter. But so far I could not receive any results from the device.

To be honest, I do not know how the ModBus RTU is configured at this cheap China energy counter I purchased for this training/testing purpose: https://de.aliexpress.com/i/1005006439685728.html?gatewayAdapt=glo2deu
Sadly nothing mentioned in the short manual and therefore testet some device adresses and tried to receive raw data to find anything at all.

Can you advice/help how would you recommend to structure this testing to be sure the ModBusBridge is working and after this how is best way to find the usable configuration of such devices? Guess that there is not sth available like automatic scanner to check if sth responding at this adresse or register? Thank you very much in advance for your support in learning sth new.

[jeroenst]

Try to use hardware rx tx gpio 1 & 3 and see if that gives different results.

I installed the latest version of Tasmota last week and modbusbridge works fine with it.

Also check your serial settings, usually 8N1 and baudrate.

See modbusbridge manual for more information.

https://tasmota.github.io/docs/Modbus-Bridge/

[RaW79]

Thx, tried now GPIO 1 & 3 but no other result so far.

Will keep on testing. Is Version 13.4.0 latest you are reffering to?

[jeroenst]

I don't have any experience with the esp32s2 and I don't know how serial communication on this device works.

Check if rx and tx are not swapped, check baudrate and serial configuration.

If it doesn't work try a normal esp32 or esp8266 which in my case both work fine.

[RaW79]

Thx. Tested with swapped RX/TX but same result = no result.
Guess their are too many variables to try because I don´t know anything about the Modbus configuration of the energy counter.

Asked the seller and i`m waiting for reply but I´m not so confident getting valuable feedback. So I´m still unsure if the problem is located at the ESP/Tasmota or if the device/Energy Counter is to be fixed.

[joba-1]

too many variables

that's what I thought.
var1: how does tasmota modbus bridge work (that is probably done, you could verify with a logic analyzer if something reasonable comes out of TX)
var2: what is the logic level of your RS485 board? (Needs to be ~3.3V, could be VCC or something fixed, then often 5 or 3.3V, if you have a second one you could connect A/B/Gnd to see if its RX led is blinking)
var3: which commands does the meter expect. As slave it will only react if addressed correctly. That is probably the most difficult, since there are soo many options. Hard to guess - finding a datasheet for the meter is the most promising way

[RaW79]

Thx. Will keep on asking the seller due to there seems to be No common Standard which Adresses are usally used. I would even then did Not know but after your confirmation will keep asking the seller until getting sth useful or do you speak Chinese as seems to be in this given picture from seller:

[joba-1]

My chinese is enough (although not existent) to see it answers the variable4 I forgot to mention: the serial protocol parameters: 9600 baud, even parity, 8 bit bytes and one stop bit.

You still need to know which bytes to send. Yes there are (not always used) standards, but that is not my expertise.

What helped me in the past if sellers/manufacturers are not helpful was searching for the device on github

[RaW79]

Thanks. May I ask because i cannot find in the docu what protocol number this is to be configured? There is as example only given protocol number 3 which is 9600,8,N,1 but according your help I need 9600,8,E,1

[jeroenst]

ModbusSerialConfig 8e1

[RaW79]

Thanks. Seller replied and in addition to the Modbus configuration (9600 8e1) I checked the wirering and the voltage level (3,3V) which seems to be ok according available specs of the TTL converter.
Based on the document from the seller (see attached) I tried to read the meter data (voltage or ampere) but at the end I´m still not able to get a result back from the device:
MODBUs-ENG.pdf

The mentioned CRC check is automatically added by the Modbus bridge?

Kindly ask to check if you can see a big mistake I´m still doing?

[RaW79]

Thanks for your guidance! With fresh eyes in the morning and the confidence in having the right adresses it´s getting easier :)

Having a look at the TTL converter, there a two LEDs (RX/TX) and by sending the Modbussend-command the RX-LED was shortly on. Therefore it was obvouis that RX/TX is assinged wrong in the configuration and after changing this this time, everything is working fine!

So even 3,3V for powering the TTL according spec works fine. So finally a problem before the screen and the Modbus Bridge is perfect!

Thanks!

[jeroenst]

You didn't give up and succeeded! Good job!