ModBus RS485

[LEOOZERAN]

Please advise. I want to use a Devtronic Black Pill CNC controller on the board. ModBus via RX/TX. But I can't figure out which pin is on the board. I'm connecting to EN. RS485 drivers. Spindle enable. Or spindle PWM control. !!!!!,,,,,???????

[terjeio]

Use PA9 and PA10 (USART1_TX and USART1_RX) - according to the map file. You have to add a UART <> RS485 converter that can do auto direction switching.

[LEOOZERAN]

Sorry. I understand. But which pin should I use for switching? Midpoint, RE/DE. Which pin does it connect to?
https://components101.com/ics/sp3485-half-duplex-rs485-transceiver-ic

[terjeio]

You can use any pin that can be mapped as output and is not in use
#define MODBUS_DIR_AUX n where n is the aux output to the map.
I can be a motor 3 pin if a ganged axis or A axis is not in use, a PWM spindle pin or a coolant pin. Or buy an auto switching converter, it does not need a direction signal.

[LEOOZERAN]

I need to know the spindle rotation direction (M3, M4). This is for a lathe. Can I use the PWM output? Or the spindle on/off contact? The latter option suits me better. I need precise operation and correct ModBus functionality. I have written and continue to write postprocessors for lathes and milling machines. The motor must operate correctly. It has a braking resistor that is activated during milling or drilling. According to the BLACK PILL schematic, the PWM contact is connected. Is this correct? I have some doubts. I am assembling my own circuit. Without using PWM. And some other components. By replacing them, others.

[LEOOZERAN]

I'm using this diagram simply as a reference. But I'd like to add... an SD card. For changing tools. I'm not a programmer and use Web Builder. And I'd like to propose a new diagram. For the developers' consideration. For editing the firmware. For Raspberry Pi and Linux. I used this diagram. But Raspberry Pi has a separate pin. For enabling RS485.

[terjeio]

But I'd like to add... an SD card. For changing tools.

You will have to select a different board map or create your own for that. And you cannot use a STM32F401 based Blackpill with SD card and expression support enabled, there is not enough flash memory for the code. A F411 will work.

And I'd like to propose a new diagram. For the developers' consideration.

@nickshl is the developer, you will have to discuss this with him.

[LEOOZERAN]

https://github.com/Devtronic-US/CNC-Controller
I'm building exactly the same board. Version 2.0. It's based on the F411. It's a board for a lathe and milling machine. Two in one. A maximum of four axes is enough. The limitation is just three limit switches. A cooling button is also not needed. Everything will be mounted on a stand on separate components. I think 4-5 pins can be allocated. For the SD module. The question remains: which pin should I use? For on/off? RS485? We discussed this at the beginning. The rest will follow as the project progresses.

[terjeio]

I have routed the PWM output as direction when PWM output is not used (no PWM spindle enabled). It seems that this is level shifted to 5V so take that into account.

Since it seems you are redesigning the board a new map is required, at least if you want SD card support. If your version is only for private use I will not add your map to the repository, name yours my_machine_map.h and enable that in my_machine.h and compile yourself. You are then free to select the pin mapping as long as the pins are capable of handling the functions assigned to them.
If the design for the redesigned board is either published (preferably) and/or the board will be commercially available I will accept a PR for a new map.

[LEOOZERAN]

So, I need to connect the A8 Spindle PWM(EN) pin to the RS485 driver. On and off. I get 3.3 volts through a resistor. Correct? What about the board? I plan to make it open source! As for compiling the board, I'll figure it out somehow. Maybe. If worst comes to worst, I'll ask for help.

Thanks for your help! It means a lot to me. Your solution. Control boards. It's already close to Linux CNC. But much clearer. Moreover. I'm Ukrainian, and Sender has Russian. It simplifies a lot.