KNOT, Modbus, Mean well.. how?

[sirbryan]

For lack of a better spot to put this, I’m dropping it in general.

I’m having a heck of a time getting a KNOT to talk to a mean well DRS-240 unit that has modbus exposed on an rj45/8x8 connector. pins 6(+) and 7(-) on the mean well running to A+ and B- on the KNOT. … I’ve also tried hitting this from a modbus client over TCP through the KNOT and it also doesn’t respond. using device ID 0x03 or 0x83 (mean well guide suggests 0x83 for ID)
Thanks.

I spent a couple hours on this, then on a whim, I swapped + / - wires from the KNOT to the DRS-480-48. [Edit: looks like the KNOT is reversed.]

The DRS address by default is 0x83 = 131. To change it you have to connect pins A0 and/or A1 to GND.

The example they give in the manual of querying the manufacturer (0x00800006, translates to register 128, grab 6 bytes) works via TCP, but /iot/modbus/transceive doesn’t work (on 7.14b3).

I tested this using the app ModMaster on macOS (cheapest one I could find that didn’t require compiling or writing anything). It connects to the KNOT just fine and sends/receives the data as expected.