[Python] Why can't I read registers using pymodbus from my Oriental Motor AZD-AD?

I'm attempting to use pymodbus to drive Oriental Motor's AZD-AD. I can drive it with no issue - the code below moves the motor as I expect it to.

import time
from pymodbus.client import ModbusSerialClient


client = ModbusSerialClient(port="COM3",
baudrate=115200,
timeout=8,
parity='E',
stopbits=1,
bytesize=8)

client.connect()

client.write_register(address=0x501, value=0x0007, slave=1) # set continuous operation
client.write_register(address=0x481, value=0x1388, slave=1) # set speed to 5000 Hz
client.write_register(address=0x601, value=0x0adc, slave=1) # acceleration of operation unit 1X10^-3 ms^-1/kHz
client.write_register(address=0x681, value=0x0adc, slave=1) # deceleration of operation unit 1X10^-3 ms^-1/kHz
client.write_register(address=0x401, value=0x0BB7, slave=1) # set number of steps (3000 steps between each position)
client.write_register(address=0x07D, value=0x0010, slave=1) # send ZHOME command
print("home")

time.sleep(5)

client.write_register(address=0x501, value=0x0002, slave=1) # set absolute positioning

client.write_register(address=0x07D, value=0x0000) # stop
client.write_register(address=0x07D, value=0x0008) # start

res = client.read_holding_registers(address=0x07D, slave=1, count=1)
print("response: ", res)

client.close()



The issue is, whenever I attempt to read data from any of the registers, my response looks like this:

response: ReadHoldingRegistersResponse(dev_id=1, transaction_id=0, address=0, count=0, bits=[], registers=[], status=1)


I should also add that I'm using a BB-USPTL4 USB to RS485 adapter between the PC and AZD-AD since my PC has no RS-485 port.

I've tried changing the count to 1-16 and looking at different registers, but the result is always the same "ReadHoldingRegistersResponse". With the AZD-AD powered off, I still get the same response which tells me that pymodbus isn't really getting data from the device.

Using MEXE02, the companion software to the AZD-AD, I ensured that the ID is indeed 1, and that my baud rate, timeout, parity, and stopbit settings all match between the software and hardware.

What am I missing? Thanks in advance.

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