GRIDBluFly Setup Guide for Serial Bluetooth Communication

The GRIDBluFly is a Bluetooth serial adapter that wirelessly replaces an RS232 cable. A serial device connects to the GRIDBluFly through its DB9 port. A PC or laptop connects wirelessly via Bluetooth, creating a virtual COM port for two-way serial communication.

This guide covers the full setup process from factory reset to verified communication.

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Before you start

Set all 4 DIP switches on the GRIDBluFly to OFF. These are located on the side of the device.

Switch	Label	Position
1	Factory Defaults	OFF (unless resetting)
2	Auto Discover	OFF
3	Auto Master	OFF
4	Fixed @9600	OFF (unless needed)

All switches in OFF position (pushed to the right). ON is to the left, OFF is to the right, as indicated by the arrows printed on the device.

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1. Factory reset (if needed)

If the device was previously configured or is not responding as expected, perform a factory reset before continuing.

Switch 1 (Factory Defaults) in ON position (pushed to the left).

1. Set Switch 1 (Factory Defaults) to ON
2. Power on the GRIDBluFly
3. Leave Switch 1 ON during configuration. Turn it OFF when done.

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2. Verify the baud rate

The GRIDBluFly must be configured to match the baud rate of the serial device it is connected to. Use a terminal emulator (Tera Term recommended) connected to the GRIDBluFly's serial port to check and set this.

Open the serial connection

Connect to the GRIDBluFly's serial COM port with these settings:

Setting	Value
Speed	115200 (factory default, adjust if needed)
Data bits	8
Parity	None
Stop bits	1
Flow control	None

Make sure Data, Parity, Stop bits and Flow control match exactly. Set Speed to match your device's baud rate.

Enter command mode

Type exactly, without pressing Enter:

$$$

The device responds with CMD and the Status LED blinks rapidly.

Check current settings

D

Look for the Baudrt field. If it does not match your serial device's baud rate, change it now.

Output of the D command showing current device settings

Change baud rate (if needed)

Use the SU command followed by the value from the table below. Only the first 2 characters of the baud rate are used.

Baud rate	Command	Baud rate	Command	Baud rate	Command
1200	SU,12	19200	SU,19	115200	SU,115K
2400	SU,24	28800	SU,28	230400	SU,230K
4800	SU,48	38400	SU,38	460800	SU,460K
9600	SU,96	57600	SU,57	921600	SU,921K

Note: Rates above 9600 use abbreviated notation. 115200 is SU,115K, not SU,115200.

Reboot to apply: R,1

After reboot, reconnect with the new baud rate and verify with $$$ and D again.

Once the baud rate is confirmed, set Switch 1 (Factory Defaults) back to OFF.

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3. Pair the PC via Bluetooth

1. Go to Settings > Devices > Bluetooth & other devices
2. Click Add Bluetooth or other device, then select Bluetooth
3. Select GRIDBluFly-XXXX from the list (XXXX = last 4 digits of MAC address). Do not select the -BLE variant.
4. If asked, enter PIN 1234 and click Connect. Some versions of Windows complete pairing without asking for a PIN.
5. Open Device Manager > Ports (COM & LPT). Two new COM ports appear labeled Standard Serial over Bluetooth link.
6. Start with the highest numbered COM port. If it does not connect, try the next lower one.

   

   Tera Term showing the two Bluetooth COM ports. Start with the highest numbered one.

7. The Bluetooth manager may show the device as Not connected or Disconnected even after successful pairing. This is normal. The device only shows as connected when a terminal emulator has the COM port open and data is actively flowing.

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4. Verify the connection

Open a terminal emulator on the PC using the Bluetooth COM port. Use the same baud rate and serial settings as section 2.

1. Exit command mode if still active: type --- and press Enter. Expected response: END
2. Type from the PC. Text should appear on the serial side.
3. Type from the serial side. Text should appear on the PC.
4. Both directions working = tunnel is operational.

Command mode can also be entered from the Bluetooth side using $$$. This only works within 60 seconds of power-up.

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Status LED reference

LED behavior	Meaning
Solid ON	Connected and active
Slow blink (1x/sec)	Idle, discoverable
Medium blink (2x/sec)	Boot up, ready for configuration
Fast blink (10x/sec)	Command mode active

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Quick command reference

Command	Action
$$$	Enter command mode
D	Display current settings
SU,[value]	Set baud rate (see table above)
R,1	Reboot and apply changes
---	Exit command mode
SF,1	Restore factory defaults
SP,xxxx	Change pairing PIN

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Important notes

• If you are migrating from a FireFly device and experiencing pairing issues, see: Migrating from FireFly to GRIDBluFly? Try these settings
• The GRIDBluFly supports RS232 only. It does not support RS485.
• All devices on the serial network must use the same baud rate.
• Default pairing PIN is 1234. This can be changed with the SP command.
• Switch 1 must be set back to OFF after configuration is complete.
• If using Linux, use cat or similar raw tools. minicom and screen may drop bytes due to RS232 signal handling.