Baud rate and serial port
Pick the right port for your machine. Match Beam Bench's baud rate to the firmware.
The two basics of serial connection: which port (which USB device) and which baud rate (how fast the bytes flow). Get either wrong and you see no response or garbled responses.
What you need
- The machine connected via USB.
- A few minutes.
Picking the port
macOS
Ports look like /dev/tty.usbserial-1410 or /dev/cu.usbserial-1410. Use the cu. variant when given a choice.
Open Beam Bench → Laser Control → connect dropdown. The list of ports comes from the OS. If your port is missing, see Port is not listed.
Windows
Ports look like COM3, COM4. Check Device Manager → Ports (COM & LPT) to see which COM number your machine got. If you see "USB Serial Device" without a driver, install the appropriate driver (CH340, CP210x, FTDI, depends on your controller).
Linux
Ports look like /dev/ttyUSB0 or /dev/ttyACM0. List them with ls /dev/ttyUSB* /dev/ttyACM*. You may need to add yourself to the dialout group:
sudo usermod -aG dialout $USERLog out and back in for the change to take effect.
Picking the baud rate
Most GRBL controllers default to 115200. Some older builds use 9600.
If you do not know:
- Start with 115200.
- Try to connect.
- If you see garbled output (random characters where the welcome message should be), the baud is wrong.
- Disconnect and try the next likely value.
Beam Bench's Connection dropdown lists: 9600, 19200, 38400, 57600, 115200, 230400.
Two ways to set it
In Beam Bench
Device Settings → Connection tab → Baud Rate. Stored on the profile, used for every connection.
In the firmware
You can change GRBL's expected baud rate by recompiling. Most people do not need to, the default works.
Verify it worked
- Laser Control shows Connected.
- The Console panel shows the GRBL welcome message (something like
Grbl 1.1h ['$' for help]) without garbled characters.
When something is wrong
- No response at all → the port is wrong, or another program holds it open, or the controller is unpowered.
- Garbled response → baud rate mismatch.
- Connection drops randomly → cable / connector / power issues. See Disconnects mid-job.