Need Information about Implementing of Modbus protocol in fp

[Swapnil Patil]

Hello folks,

I wanted to implement Modbus protocol on fpga. I don't know how to start? I read various documents on internet but didn't got any clear idea. basically my aim is to make package of this protocol. I am using Vhdl as language. so i want process or say steps should i follow to make this protocol working.If anybody has worked on this previously can share document it will be great help.
thanks in advance..!!

 

[David Brown]

On 26/11/18 11:08, Swapnil Patil wrote:

Hello folks,

I wanted to implement Modbus protocol on fpga. I don't know how to
start? I read various documents on internet but didn't got any clear
idea. basically my aim is to make package of this protocol. I am
using Vhdl as language. so i want process or say steps should i
follow to make this protocol working.If anybody has worked on this
previously can share document it will be great help. thanks in
advance..!!

There are basically two ways to do Modbus. One is Modbus RTU, using a
UART with RS-485. On the hardware side you need a UART with a transmit
enable control line. Everything else is in software.

The other is Modbus TCP/IP over Ethernet. On the hardware side, you
need Ethernet. Everything else is in software.

So "Modbus on an FPGA" means having a processor (soft or hard) and
software on the FPGA or the board, and a UART or Ethernet. Trying to
implement Modbus directly in FPGA hardware without a processor is insanity.

 

[Swapnil Patil]

On Monday, November 26, 2018 at 3:42:10 PM UTC+5:30, David Brown wrote:

On 26/11/18 11:08, Swapnil Patil wrote:
Hello folks,

I wanted to implement Modbus protocol on fpga. I don't know how to
start? I read various documents on internet but didn't got any clear
idea. basically my aim is to make package of this protocol. I am
using Vhdl as language. so i want process or say steps should i
follow to make this protocol working.If anybody has worked on this
previously can share document it will be great help. thanks in
advance..!!


There are basically two ways to do Modbus. One is Modbus RTU, using a
UART with RS-485. On the hardware side you need a UART with a transmit
enable control line. Everything else is in software.

The other is Modbus TCP/IP over Ethernet. On the hardware side, you
need Ethernet. Everything else is in software.

So "Modbus on an FPGA" means having a processor (soft or hard) and
software on the FPGA or the board, and a UART or Ethernet. Trying to
implement Modbus directly in FPGA hardware without a processor is insanity.

Thanks David for information. I just wanted to know that are you suggesting to use external processor for implementation.

and also i would like to know while writing vhdl program what steps should i follow.

 

[David Brown]

On 26/11/18 13:09, Swapnil Patil wrote:

On Monday, November 26, 2018 at 3:42:10 PM UTC+5:30, David Brown
wrote:
On 26/11/18 11:08, Swapnil Patil wrote:
Hello folks,

I wanted to implement Modbus protocol on fpga. I don't know how
to start? I read various documents on internet but didn't got any
clear idea. basically my aim is to make package of this protocol.
I am using Vhdl as language. so i want process or say steps
should i follow to make this protocol working.If anybody has
worked on this previously can share document it will be great
help. thanks in advance..!!


There are basically two ways to do Modbus. One is Modbus RTU,
using a UART with RS-485. On the hardware side you need a UART
with a transmit enable control line. Everything else is in
software.

The other is Modbus TCP/IP over Ethernet. On the hardware side,
you need Ethernet. Everything else is in software.

So "Modbus on an FPGA" means having a processor (soft or hard) and
software on the FPGA or the board, and a UART or Ethernet. Trying
to implement Modbus directly in FPGA hardware without a processor
is insanity.

Thanks David for information. I just wanted to know that are you
suggesting to use external processor for implementation.

I am suggesting you use a processor for handling the protocol. It is
entirely up to you if this is external to the FPGA, a hard core in the
FPGA, or a soft core in the FPGA.

and also i would like to know while writing vhdl program what steps
should i follow.

If you have to ask this, I would recommend that you drop the idea of an
FPGA altogether. A $2 microcontroller will let you build a Modbus RTU
slave on RS-485 - it will have a UART and all the processing power you
need. If you are thinking of Modbus over Ethernet, your microcontroller
will be around $5.