Modbus - How would you do it?

[Lare]

Here is Siemens mb_master sequencing example for 1500 CPU. You can take pseudo for code to 1200.


https://support.industry.siemens.com/cs/ww/en/view/68202723

 

[goghie]

This is a common misconception. The RS-485 limit is 32 Unit Loads. Historically, most RS-485 devices were 1 Unit Load, so 1 Device = 1 Unit Load. However, modern RS-485 transceivers are a fraction of a Unit Load, such as 1/4, 1/8, 1/10, etc. Therefore, with 1/8 Unit Load devices, for example, you can actually have up to 256 devices on one RS-485 bus (assuming the protocol used can logically support all of those addresses - note that Modbus RTU is limited to addresses 1 - 247).

Until producers of equipment start to write in datasheet what is impedance of it's trancievers I will use 1 UL for calculation.

 

[Puddle]

I have a noob question. I've decided to be fancy and put the time and date on my HMI and because it will drift over time, I've put in a facility to modify the time and date from the HMI.


The program works fine, but I cannot for the life of me work out what format the date fields wants to see the input. I used a date/time field and it would just return to zero, so I split it into seperate date and time fields. Time updates, date will not. I'm using dd/mm/yyyy format. I've tried dd/mm/yyyy, dd/mm/yy, d/m/yy, same again using . instead of / and with a space and just as a number.
What am I missing?

 

[Puddle]

I have a noob question. I've decided to be fancy and put the time and date on my HMI and because it will drift over time, I've put in a facility to modify the time and date from the HMI.


The program works fine, but I cannot for the life of me work out what format the date fields wants to see the input. I used a date/time field and it would just return to zero, so I split it into seperate date and time fields. Time updates, date will not. I'm using dd/mm/yyyy format. I've tried dd/mm/yyyy, dd/mm/yy, d/m/yy, same again using . instead of / and with a space and just as a number.
What am I missing?

Anybody? Whatever I input into the date field it just returns to zero.


The information says "If the operator ignores the syntax when entering values or enters invalid values in Runtime, these entries will not be applied."


None of the documation I've found indicates that the syntax should be any different to the HMI language settings.

 

[Lare]

Anybody? Whatever I input into the date field it just returns to zero.


The information says "If the operator ignores the syntax when entering values or enters invalid values in Runtime, these entries will not be applied."


None of the documation I've found indicates that the syntax should be any different to the HMI language settings.

You should start new thread for this and also tell which HMI you are using. (Siemens or non Siemens and type)



Siemens time and date is 7 bytes long BCD coded variable and thinking that not all HMIs can read that variable directly or correctly.


But you can use RD_SYS_T block and then have time and date on separate unsigned integers. Then draw "/" between different values and it works on every HMI.


Look code sample from youtube.

https://www.youtube.com/watch?v=GLZP7b4HgAA

 

[Puddle]

You should start new thread for this

I'll start one on monday as I won't be able to test anything until then.

and also tell which HMI you are using. (Siemens or non Siemens and type)

Siemens KTP400 Basic panel.



HMI is reading and sending perfectly, tried both as DTL and combining seperate Date and Time_Of_Day and even having seperate boxes for each byte to write year, month and day.

 

[Lare]

I'll start one on monday as I won't be able to test anything until then.





Siemens KTP400 Basic panel.



HMI is reading and sending perfectly, tried both as DTL and combining seperate Date and Time_Of_Day and even having seperate boxes for each byte to write year, month and day.

Is your input field type input only or in/out?