Changing an Isel FB2 to LinuxCNC?

I think a RS-232 to RS-485 adapter maybe would not work, because the (chain of) LS-173 uses full duplex (4 wire) RS-485, and I think RS-232 only does half duplex.

Sadly, that maybe also means that a Raspberry Hat would probably not work, because looking at the pinout of the Raspberry, it also has only two pins labels RX/TX, though I guess some IO pins may be re-purposed if the hat comes with a full duplex serial port driver.

So in summary, I still like the 7C81 option best, also because I like the form factor, I have several Raspberries lying around, and it is one of the few boards that are in stock in the EU...

Though I do like the simplicity of the HAL driver (.comp) for the serial port, this was easy to follow even for me, and I think I understand how HAL works now . My initial confusion came from thinking I would have to translate G commands into servo driver commands in the HAL driver, which I understand now is of course not needed.

andypugh wrote:

Ah, I see! That makes sense now. Then I'll try the serial option - that would seem to be both the easiest and cheapest approach.

Thanks for all the help!

I'm going through old Logosol posts. I'd appreciate hearing where you are on this project.

You can communicate from a PC to a chain of Logosol drives with a USB to RS-485 converter. No Mesa ports to work with.
These converters typically use a chip like an FTDI for USB-to-UART conversion, plus an RS-485 transceiver (like a MAX485) to handle the differential signaling and half-duplex operation on the bus.
RS-232 vs RS-485:
RS-485 is half-duplex (not full duplex). It uses two wires (A/B or +/-) that are shared for both transmitting and receiving - devices take turns communicating on the same pair. RS-232 is full-duplex, using separate transmit and receive lines.
The key advantage of RS-485 is differential signaling, which eliminates common mode noise and allows much longer cable runs (up to 4,000 feet) compared to RS-232's typical 50-foot limit.
RS-232: Uses separate RX, TX, and GND lines. Single-ended signaling measures voltage relative to ground.
RS-485: Uses differential pairs (A/B or +/-). The receiver compares the voltage difference between the two wires to determine logic levels. Since noise affects both wires equally (common mode), it cancels out in the differential measurement, making the signal much more robust.