[TriEmbed] ADC

[Rodney Radford]

Please provide a link to the modbus library you use.

This is where I found the information I saw about RTU on RS-485 board

https://www.arduino.cc/en/ArduinoModbus/ArduinoModbus

On Mon, Oct 26, 2020 at 11:11 AM John Vaughters via TriEmbed <
triembed at triembed.org> wrote:

> oh, forgot to mention the Pi 3.3v Tx -> ard Rx is just accepted via
> threshold limits and therefore is just a direct connect.
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> On Monday, October 26, 2020, 11:08:57 AM EDT, John Vaughters via TriEmbed <
> triembed at triembed.org> wrote:
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> Rodney,
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> There are a number of modbus libraries out there, so I'm not sure which
> one you are referring to. Yes, when I said UART, I specifically meant TTL.
> I use a very simple voltage divider for the ard Tx -> Pi Rx with one
> resister value and 3 resistors. I think I have used both 10k and 1k ohms
> and parallel two resistors to get half the value and series the third
> resistor. This gives you a super simple interface to the arduino that is 5V
> -> 3.3 Pi. I use the 5V pin of the Pi to power the 5v pin of the arduino.
> GND common of course. I use the simple-modbus Library code and I hesitate
> to give you a link, because in doing a quick search, I am not sure which
> code I am currently using, but the concept of this library is to use a very
> minimal set of modbus functions with holding registers only. This can be
> used to gang bits into a single register for binary, if I remember
> correctly. Thinking from the top of my head, so check that. I think you
> will find a couple forks of the original simple-modbus. Then I pass it onto
> mbusd to convert it TCP. So the serial is MODBUS RTU and mbusd converts it
> to MODBUS TCP.
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> What I like about this config and have been using it for a couple years is
> it is super reliable. UART being one of the oldest most reliable comms and
> MODBUS being one of the oldest most reliable industrial protocols, it makes
> for a a very reliable and recoverable from hard reboot combination.
> However, there are even more complete modbus libraries that I have used in
> the past, but simple-modbus, well..... is simple :)
>
> John Vaughters
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> On Monday, October 26, 2020, 10:23:19 AM EDT, Rodney Radford <
> ncgadgetry at gmail.com> wrote:
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> I have not used the modbus Arduino code before, but it does look
> interesting. However in reading the description they state it is designed
> to use with either their Ethernet shield or the RS485 shield, but I did not
> see anything on running it with just a standalone Arduino. If it is
> possible to just use the TTL serial port of the Arduino, that would be very
> nice, indeed.
>
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