Hypertherm board pinout for RS485 extension board

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20 Oct 2020 14:16 #186684 by radek_marko
I have also plan to test serial comms over RS485



Plasma => RS232 TTL 3.3V => converter board RS485 => twisted pair RS485 => RS485 to USB connected to laptop

I'm struggling with ModBus apps - they do not support ModBus ASCII, the free version of app with ASCII support executes only 6 reads and writes :(
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20 Oct 2020 15:40 #186702 by rodw
There is no need to experiment with Modbus. The Hypertherm serial port is fully supported in Plasmac. Phill and thefabricator03 have done it all for you.

if you really wanted to have fun, get modbus ASCII for Hypertherm working over the Mesa Smart serial port....

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20 Oct 2020 16:11 #186705 by radek_marko
Aha! I was planning to connect serial ports to my Windows laptop, not to LinuxCNC!

I do not know if USB converters will be recognized in Linux.

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20 Oct 2020 16:26 #186708 by snowgoer540

Aha! I was planning to connect serial ports to my Windows laptop, not to LinuxCNC!

I do not know if USB converters will be recognized in Linux.


Maybe I've gotten lost in the thread... but what exactly are you trying to achieve?

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20 Oct 2020 20:13 #186742 by radek_marko
OK, just returned from the workshop and I couldn't get any communication on J11 (expected RS232)

Connection tested using serial params 19200,8,EVEN,1, I've tried several ModBus ASCII apps, even sending a single command as per serial reference doc - no response from the plasma unit.

I think the issue might be in "ENABLE SIGNAL". I've tried to leave it not connected, supply 3.3V to it or connect it to the ground - no joy.
Are there are any proud owners of RS485 board here who have any electronic knowledge and are willing to check how this signal is connected on the original board?

Maybe I've gotten lost in the thread... but what exactly are you trying to achieve?

Initially, I was expecting that data available over ModBus / serial link might be sufficient to make PlasmaC act as THC (e.g. by reading arc voltage and adjusting torch hight). That was clarified by Tommylight as a not appropriate approach.

Looking on the pinout make me curious and check if signals on connector J11 on the mainboard are RS232 (3.3V TTL to be more specific) and if those signals can be used for ModBus coms without the original extension board.

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20 Oct 2020 20:25 #186744 by rodw
Have you reviewed the Hypertherm protocol document (attached)?
Only a very small set of commands are supported.
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20 Oct 2020 20:50 #186747 by radek_marko
Have you reviewed the Hypertherm protocol document (attached)?
Yes, I did -
I've tried commands from the manual - e.g. ":01062093000145" for setting the cutting mode and few more.

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20 Oct 2020 21:00 #186750 by rodw
I''m wondering if the enable pin is not meant to be tied to CTS or RTS (or tied to both)

Normally CTS would be connected to the opposite side RTS and vice versa

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20 Oct 2020 21:28 #186754 by radek_marko
I''m wondering if the enable pin is not meant to be tied to CTS or RTS (or tied to both)
If there would be a flow control required then it would be in the RS485 serial link spec and I do not see it - baud rate, data, parity and stop bits are specified, but not the flow control.

The other aspect is that usually if I'm working with printers or other devices with CTS/RTS, supplying +V or connecting those signals to the ground tricks the device and makes it think that there is a valid signal and the communication can commence.

I have all of the pins from J11 at the back of the unit now, so I can come back to it and can keep digging and checking other theories.

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20 Oct 2020 21:37 #186756 by rodw
If you have a look at the UART on an Odroid H2+, it has 4 pins RX, TX, RTS, CTS. You are not talking about the RS485 part here but the interface to the Hypertherm's UART> Perhpas you can trace back to a chip on the board inside the plasma cutter and pull a data sheet. So long ago since I played with serial ports!

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