No permission to access Polar USB device

[loukad]

Hi Cédric,

Thank you for putting together this software. I am trying to view the file system of a Polar OH1 HRM on a Mac, and am getting the following error coming from libusb:

❯ ./polar_ftp
Traceback (most recent call last):
	7: from ./polar_ftp:30:in `<main>'
	6: from ./polar_ftp:30:in `new'
	5: from /Users/louka/code/polar/lib/polar_ftp.rb:13:in `initialize'
	4: from /Users/louka/code/polar/lib/polar_usb.rb:24:in `detect'
	3: from /Users/louka/code/polar/lib/polar_usb.rb:24:in `new'
	2: from /Users/louka/code/polar/lib/polar_usb_hid.rb:14:in `initialize'
	1: from /usr/local/lib/ruby/gems/2.7.0/gems/libusb-0.6.4/lib/libusb/dev_handle.rb:79:in `claim_interface'
/usr/local/lib/ruby/gems/2.7.0/gems/libusb-0.6.4/lib/libusb/constants.rb:68:in `raise_error': LIBUSB::ERROR_ACCESS in libusb_claim_interface (LIBUSB::ERROR_ACCESS)
	6: from ./polar_ftp:30:in `<main>'
	5: from ./polar_ftp:30:in `new'
	4: from /Users/louka/code/polar/lib/polar_ftp.rb:13:in `initialize'
	3: from /Users/louka/code/polar/lib/polar_usb.rb:24:in `detect'
	2: from /Users/louka/code/polar/lib/polar_usb.rb:24:in `new'
	1: from /Users/louka/code/polar/lib/polar_usb_hid.rb:5:in `initialize'
/Users/louka/code/polar/lib/polar_usb_hid.rb:21:in `rescue in initialize': No permission to access Polar USB device (PolarUsb::PolarUsbDeviceError)

My understanding is that libusb cannot claim the device because a kernel driver has already attached to it. But even after running:

sudo kextunload -b com.apple.driver.usb.IOUSBHostHIDDevice

and reconnecting the device, the error persists.

Any idea what the problem is?

Thanks,
Louka

[cmaion]

Hi,

I don't use a Mac so can't really help here.

I believe Apple did made a change a while back that results in this error, but didn't investigate further... It may require replacing libusb with some native macos-only USB interface library to solve this.