I am trying to connect an older LeArm robotic arm to a Windows PC using the LeArm 2.1 software, but I cannot get the arm to appear as a usable serial device.
The arm has a Mini-USB connector, so I believe it is the older/original LeArm controller rather than the newer Type-C/ESP32 LeArm AI version.
What I have done
Downloaded and installed the LeArm 2.1 & 2.2 software.
Installed the supplied/expected USB drivers.
Connected the arm with a Mini-USB cable.
Powered the arm using its external power supply and verified the arm power switch is on.
Checked Windows Device Manager under:
Ports (COM & LPT)
Universal Serial Bus controllers
Other devices
Tried to identify the port by unplugging and reconnecting the arm.
What I am seeing
Device Manager shows a persistent USB Serial Port (COM3), but it stays present even after the LeArm is unplugged. Therefore, I do not believe COM3 belongs to the arm.
I also see UCM-UCSI ACPI Device under USB Connector Managers, but I understand this is a Windows USB-C/power-management device and not the LeArm.
Plugging and unplugging the LeArm does not create or remove an obvious device under Ports, USB controllers, or Other devices.
In UART Assistant, the Channel dropdown is empty; no serial port is available to select.
I do not see an Unknown USB Device, CH340, CP210x, FTDI, Prolific USB-serial device, or any new COMx entry that changes with the arm connection.
Thanks for the detailed description. The LeArm control board connects to the PC through an onboard USB-serial chip, and in Device Manager it should appear as a CH340/CH341 serial port — the official LeArm manual notes that “有 CH340 名称的 COM 即为我们这个机械臂的端口” (the COM with a CH340/CH341 name is the arm’s port, not COM1 which is usually a system port). Since nothing at all appears when you plug the arm in (no new COM, no unknown device), please try these checks in order:
Cable: Confirm the Mini-USB cable is a real data cable, not a charge-only cable. A charge-only cable is the most common reason a board shows nothing in Windows. Try a different Mini-USB data cable and a different USB port (preferably a rear USB 2.0 port).
Driver: Install the CH340/CH341 serial driver (ch341ser.exe) that ships with the LeArm host-software package (it is located in the “01 驱动文件” / driver folder of the installation package). With the arm plugged in, if a device with a yellow exclamation mark appears under Device Manager, right-click it and choose “Update driver” to install the driver manually.
Power: Keep the arm powered through its DC adapter with the power switch on while the USB cable is connected — the official procedure connects power and switches the arm on first, then connects USB.
Device Manager tips: Enable View > Show hidden devices in Device Manager, then plug/unplug the arm and watch for any new entry under Ports (COM & LPT) or Universal Serial Bus controllers. Note the COM number if one appears.
Software settings: In the LeArm host software, select the board’s COM port and set the baud rate to 9600 (do not use 115200), then click “open serial” — the icon should turn green when connected.
If no USB device ever enumerates on more than one PC after these checks, please share a screenshot of Device Manager (with hidden devices shown and devices listed by connection), a photo of the control board showing which controller it uses (STM32 / 51 / Arduino) and the board markings, and confirm exactly which LeArm software version you are running. That will help us narrow down whether the issue is the cable, the driver, or the board itself.
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If no serial port appears when connecting via USB, you can try connecting another serial device to your PC to see if it displays properly.
If other devices work normally, please try replacing the current USB cable with another one. At the same time, please check if there is any abnormally hot spot on the 6-channel Bluetooth servo controller board.