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[on:]

i'm working on Modbusmq, a modification of the libmodbus library (https://launchpad.net/libmodbus by Stephane Raimbault) for the Arduino platform. for now, it's a Modbus TCP slave.

any tester and debugger is appreciated to help me makin' a stable program.

that's the code: http://bazaar.launchpad.net/~marioquark-yahoo/modbusmq/modbusmq/files

thank you,
marioquark

[Reply #1 on:]

i am locked:
timing in TCP management doesn't work as it sould: replies are sent with a delay i don't want. this make timeout occur.

probably this happens due to a too big transmission buffer: i can't resize it! nor i can set the TCP_NODELAY option (library doesn't offer this).

any suggestion?

please help me, i think my project could be very useful!

[Reply #2 on:]

my libraty is finished and it seems to work perfectly...  ;D

[Reply #3 on:]

nice work
can you please explain a bit a about how to use it?

[Reply #4 on:]

ok. i'll write down a few lines, then i'll make a wiki for it:


modbusmq is a ModBus ( http://en.wikipedia.org/wiki/Modbus ) TCP slave (server): briefly, it holds a data map, which can be queried by Modbus clients (PC or other) with a standard protocol.

requirements:
- Arduino Ethernet Shield

usage:
Arduino side
- paste the code in a new project in the Arduino IDE
- change the network params, if needed: IP, Gateway.
- change the slave Address, if needed
- set or unset the DEBUG flag to have debug messages through serial line
PC side:
- start a modbus client to query Arduino IP, with the correct slave modbus address (there are many freeware, eg: ModScan)

TODO:
- test two slaves in the same network.
- test two masters (clients) for the same slave

[Reply #5 on:]

Hello,

I just tested the Modbusmq and so far it works fine. But I'm struggling a little with all the pointers.

I already managed to send a modbus command from a PC, which sets different bits to true.

But now I want to switch relais, which are connected to a PCF8574. For this I normally use the command:

PCF8574Write(B11111110);

Now I tried to convert the "mb_mapping->tab_coil_status" to a value which I can send with PCF8574Write. But without success. It is too long ago, that I have done somethink with pointers. I tried the following:

for (n=0;n<8;n++)
          {
            PCFStatus1[n] = byte(*(mb_mapping->tab_coil_status + n));
            
            DEBUG_PRINTLN(n);
            delay(200);
          }

This seems to me not very efficient and it is also not working.

Can someone help?

BR,

Chris

[Reply #6 on:]

PCF8574Write(B11111110);

what command is it? a function from you? from a library?

if you have to copy bytes to/from a vector, use the memcpy() standard C function. reference: http://www.cplusplus.com/reference/clibrary/cstring/memcpy/

maybe
memcpy(PCFStatus1, mb_mapping->tab_coil_status, n);

bye
quark

[Reply #7 on:]

Sounds very promising!

But I still have some problems. I tried the following:

byte PCFStatus1;
      
memcpy(PCFStatus1, mb_mapping.tab_coil_status, ;
PCF8574Write(PCFStatus1);


Here the function:
//Write data to PCF8574  
void PCF8574Write(byte _data )
{
  Wire.beginTransmission(PCF8574_ADDR);
  Wire.send(_data);
  Wire.endTransmission();
}


But I get the following error:

error: invalid conversion from 'uint8_t' to 'void*'

I do not understand it, why void*?

Any idea?

[Reply #8 on:]

Hello,

can you give some explanations for the following (is there already some wiki):

If data are correct received, how to use them in the main loop?

I assume there are the following buffers/memorys:
mb_mapping->nb_coil_status
mb_mapping->nb_input_status
mb_mapping->nb_holding_registers
mb_mapping->nb_input_registers

I have also seen some functions like "get_byte_from_bits".

Is there somewhere a more detailed explanation? Maybe in the libmodbus library?

For my problem to write data to the PCF8574 can I use the  "get_byte_from_bits" function? But how exactly?

Thank you for your help!

[Reply #9 on:]

Got it running with the following code:

int PCFStatus1;

// Gets the byte value from many input/coil status.
PCFStatus1 = get_byte_from_bits(mb_mapping.tab_coil_status, 0, ;

PCF8574Write(byte(PCFStatus1));

[Reply #10 on:]

I am having trouble getting the modbus sketch to even work on my arduino mega and ethernet shield.  Where do I edit the network settings.  I tried following the example, but I cannot even ping the arduino.  Is there some setup for the wiznet chip?  Any help would be appreciated.  I am trying to get RC servo control using modbus words.

Thanks

[Reply #11 on:]

Hello, it works fine (in my initial test), but the DEBUG flag has to be disabled because if it is enables the Arduino hangs  :-/, so I can't debug or use the serial port for interchange data.

Any idea to make it work with debug flag?.

[Reply #12 on:]

I got it working with the DEBUG flag, but it starts working only after having the serial monitor started.

I made the following network settings:
const byte gateway[] = { 192, 168, 2, 254 };
const byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
const byte ip[] = { 192, 168, 2, 100 }; // Arduino has this IP

You have to use the same subnet (192.168.2.x) as your computer uses.

BR,

Chris

[Reply #13 on:]

Can anyone give me an example how to read an input on the Arduino, and map the I/O status to be polled by the Master?

I am not sure how the mapping is handled.

[Reply #14 on:]

wow great to see MODBUS/TCP functional.  this library will certainly come in handy.