Hameg Power Meter HM8115-2 USB/RS-232 Serial interface on OS X

Although the Hameg 8115-2 Power Meter has a USB/RS-232 serial interface, there is currently no driver support for OS X. In the next few step I explain how to get the serial interface working in OS X.

USB/RS-232 serial connection.

To talk to the power meter over USB on OS X you need to ensure the HO820 interface to enumerate as a serial port. In order to achieve this you need to add the Hameg HO820 USB Serial Port (VCP) device ID to the list of 'known devices' of the OS X FTDI driver.

  1. Install the latest FDTI Virtual COM Port Driver on you machine.
  2. Edit /System/Library/Extensions/FTDIUSBSerialDriver.kext/Contents/Info.plist, add the following paragraph under the IOKitPersonalities section:

  3. Reload the FDTI driver (in case of problems see the OS X 10.10 section below):

    sudo kextunload -b com.FTDI.driver.FTDIUSBSerialDriver
    sudo kextload -b com.FTDI.driver.FTDIUSBSerialDriver
  4. Check if the driver is loaded:

    sudo kextstat | grep FTDI 

    should return something similar to:

    160    0 0xffffff7f83216000 0x8000     0x8000     com.FTDI.driver.FTDIUSBSerialDriver (2.2.18) <124 39 5 4 3 1>
  5. Look for new '/dev' entries

    ls -las /dev | grep -i usb

    should return something similar to:

    0 crw-rw-rw-   1 root  wheel      17,  11 Jan  7 19:28 cu.usbserial-00002014
    0 crw-rw-rw-   1 root  wheel      17,  10 Jan  7 19:28 tty.usbserial-00002014

Open a terminal connection (I use CoolTerm)

Port options:

  • Baudrate: 9600
  • Data Bits: 8
  • Parity: none
  • Stop Bits: 1

Send one of the following commands to test your connection:


OS X 10.10, Yosemite Issue

If you are unable to load the driver and you receive the following message in kernel buffer:

ERROR: invalid signature for com.FTDI.driver.FTDIUSBSerialDriver, will not load

you need to disable the requirement to have drivers signed. In order to do this you need to switch the kernel extensions to developer mode:

sudo nvram boot-args="kext-dev-mode=1"

Reboot and then check if the driver is loaded.


In case of problems you can check the following logs:

sudo less /var/log/kernel.log
sudo less /var/log/system.log
sudo dmesg | less