Connecting to hardware

[mwilt-rapidmicrobio]

I am very happy with this code so far, and have successfully run with both serial and Ethernet connections. I see that I can expand the register address space by changing this:
uint16_t ModbusDATA[0x100];

I see it checks for valid address using sizeof(ModbusDATA).

I have two questions:

• Any thoughts about discontinuous address space? The hardware I am replacing has registers scattered around the 16-bit address space.
• Any ideas about connecting to hardware? I need to support reading hardware to determine the current value of some registers, and also writing to hardware at some other addresses.

Mike

[alejoseb]

Hi,

• Any thoughts about discontinuous address space? The hardware I am replacing has registers scattered around the 16-bit address space.
  It is possible, it needs library modifications depending on the needed address space.

• Any ideas about connecting to hardware? I need to support reading hardware to determine the current value of some registers, and also writing to hardware at some other addresses.
  You can have a master and slave running in parallel on different serial ports. The master can be used to read and write on other hardware (slaves) also supporting Modbus.

[mwilt-rapidmicrobio]

My slave needs to write directly to hardware instead of (or in addition to) storing information in memory. I was just wondering if you have thought about how to support this. Perhaps a way to register a function that does the additional work required to update the hardware when a request comes in to write registers.

…

________________________________ From: Alejandro Mera ***@***.***> Sent: Tuesday, June 24, 2025 9:44 PM To: alejoseb/Modbus-STM32-HAL-FreeRTOS ***@***.***> Cc: Michael Wilt ***@***.***>; Author ***@***.***> Subject: Re: [External] [alejoseb/Modbus-STM32-HAL-FreeRTOS] Connecting to hardware (Issue #126) [https://avatars.githubusercontent.com/u/16860024?s=20&v=4]alejoseb left a comment (alejoseb/Modbus-STM32-HAL-FreeRTOS#126)<#126 (comment)> Hi, * Any thoughts about discontinuous address space? The hardware I am replacing has registers scattered around the 16-bit address space. It is possible, it needs library modifications depending on the needed address space. * Any ideas about connecting to hardware? I need to support reading hardware to determine the current value of some registers, and also writing to hardware at some other addresses. You can have a master and slave running in parallel on different serial ports. The master can be used to read and write on other hardware (slaves) also supporting Modbus. — Reply to this email directly, view it on GitHub<#126 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BTW6YXXAFP2JFVC76M4YNXT3FH5JBAVCNFSM6AAAAACABGA6VGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTAMBSGMZDMNZTHE>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[alejoseb]

There are a few options: registering a callback, sending a notification through RTOS, and pooling the semaphore state. The first 2 solutions need a few library changes, and the last one you can see a few examples already in the repo to toggle a led.

There are no plans to implement that functionality since it is not part of the Modbus standard.

If you can sponsor this library I can implement the needed changes and make it public.