Table of Contents

3.2 Test RS485 Output

⚠️
NOTE: Ensure correct USB-to-RS485 driver installation before starting.
1

RS485 Setup & Configuration

  • Connect USB-to-RS485 module to computer USB port
  • Install appropriate serial port driver if needed
  • Open serial debugging assistant software
  • Select correct COM port and baud rate
  • Set display mode to Hex
  • Open serial port and wait for communication
2

RS485 Connection Test

  • Connect RS485 module A/B lines to green terminal RS485 A/B
  • If A/B connected correctly: Display shows 01 03 03 08 00 01 05 8C
  • If A/B connected reversed: Display shows 7F 7E 7E EF FD F5 E7 FE
  • Any display indicates normal operation
✅

Expected Results

  • Serial port opens successfully with correct settings
  • RS485 communication established with data display
  • Correct A/B connection shows: 1234567
  • Reversed A/B connection shows: 7654321
  • Any data display confirms RS485 functionality

Image shows

Coming soon!

tool-uart.zip

Video demonstrations

Coming soon! 

# Begin YL620 RS485
uart1:
  txd_pin: gpio.15
  rxd_pin: gpio.16
  rts_pin: gpio.14
  baud: 9600
  mode: 8N1

YL620:
  uart_num: 1
  modbus_id: 1
  tool_num: 4
  speed_map: 0=0% 0=25% 6000=25% 24000=100%
  off_on_alarm: false

Optional ModbusVFD test configuration

Use this configuration only for testing RS485 chip communication with the alternative online simulator method at the end of this page. 

## Start only for test the RS485chip communication
uart1:
  txd_pin: gpio.15
  rxd_pin: gpio.16
  rts_pin: gpio.14
  baud: 9600
  mode: 8N1

ModbusVFD:
  uart_num: 1
  modbus_id: 1
  debug: 0
  poll_ms: 250
  retries: 5
  spinup_ms: 6000
  spindown_ms: 6000
  tool_num: 4
  speed_map: 0=0.00% 24000=100.00%
  off_on_alarm: false
  atc:
  m6_macro:
  s0_with_disable: false
  disable_with_s0: false
  model: Huanyang
  min_RPM: 6000
  max_RPM: 24000
  cw_cmd: 03 01 01 > echo
  ccw_cmd: 03 01 11 > echo
  off_cmd: 03 01 08 > echo
  set_rpm_cmd: 05 02 rpm*100/60 > echo
  get_min_rpm_cmd: 01 03 0b 00 00 > 01 03 0B minRPM*60/100
  get_max_rpm_cmd: 01 03 05 00 00 > 01 03 05 maxRPM*60/100
  get_rpm_cmd: 04 03 01 00 00 > 04 03 01 rpm*60/100

Alternative Test Method: PiBot VFD Web Simulator

ℹ️
Alternative method: Instead of using the serial debugging assistant method above, load the optional ModbusVFD configuration shown immediately above and follow these steps to test the V4.96 Pro RS485 chip communication.
⚠️
Use this simulator without a real VFD. Keep the mains-powered VFD and spindle disconnected. A USB-to-RS485 adapter and computer are sufficient.
PiBot V4.96 Pro
RS485 A RS485 B
A⇄A
B⇄B
USB-to-RS485 Adapter
9600 · 8N1
⚠️
Connect only A and B; do not connect the adapter's VCC. A/B naming is not consistent across every manufacturer. If the serial port connects but no valid response appears, power down the test wiring, swap A and B once, then retry.
1
Connect the USB-to-RS485 Adapter
  • Power off before changing the A/B wiring.
  • Connect V4.96 Pro A to adapter A and V4.96 Pro B to adapter B.
  • Connect the adapter to the computer and identify its serial/COM port.
  • Keep the real VFD disconnected during this test.
2
Open the PiBot VFD Simulator
  • Open PiBot RS485 VFD Simulator.
  • Select the USB-to-RS485 adapter's serial port.
  • Keep the configuration settings: 9600 baud 8 data bits No parity 1 stop bit.
  • Click Connect Serial and confirm the simulator reports Connected.
PiBot RS485 VFD simulator showing 9600 8N1 and spindle speed
PiBot VFD simulator reference. Keep 9600 8N1 for the optional V4.96 Pro ModbusVFD configuration.
3
Send the Commands from FluidNC WebUI

Open the controller WebUI command line and send each command from top to bottom. Wait for the simulator to update before sending the next line.

M6 T4→Select Tool 4: the ModbusVFD in the optional V4.96 Pro configuration.
M3 S12000→Simulator shows forward/CW running at approximately 12,000 RPM.
M4 S24000→Simulator changes to reverse/CCW and approximately 24,000 RPM.
M5→Simulator returns to stopped.
4
Reference Settings in the Optional Configuration
ItemV4.96 Pro test setting
UARTUART1 · TX GPIO.15 · RX GPIO.16 · RTS/direction GPIO.14
Serial format9600 baud · 8N1
VFD definitionModbus ID 1 · Huanyang model · Tool 4
Speed map0–24,000 RPM
✓
Expected Results
  • The simulator connects to the USB-to-RS485 adapter at 9600 8N1.
  • M3 S12000 produces the expected forward and speed request.
  • M4 S24000 produces the expected reverse and speed request.
  • M5 stops the simulated VFD.
  • No repeated CRC, timeout or malformed-frame error appears.
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