ReSpeaker USB 4 Mic Array LED Control Protocol

中文

We can control the ReSpeaker USB 4 Mic Array's LEDs through USB. The USB device has a Vendor Specific Class Interface which can be used to send data through USB Control Transfer.

On Linux, we can run lsusb -v -d 2886: to get its USB information:

Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        3
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              9 SEEED Control

The libusb's python library - pyusb is used here. The implementation is at usb_pixel_ring_v2.py

The LED control command is sent by pyusb's usb.core.Device.ctrl_transfer(), its parameters are like：

ctrl_transfer(usb.util.CTRL_OUT | usb.util.CTRL_TYPE_VENDOR | usb.util.CTRL_RECIPIENT_DEVICE, 0, command, 0x1C, data, TIMEOUT)

We only need to care about command 和 data:

command	data	note
0	[0]	trace mode, LEDs changing depends on VAD* and DOA*
1	[red, green, blue, 0]	mono mode, set all RGB LED to a single color
2	[0]	listen mode, similar with trace mode, but not turn LEDs off
3	[0]	wait mode
4	[0]	speak mode
5	[0]	spin mode
6	[r, g, b, 0] * 12	custom mode, set each LED to its own color
0x20	[brightness]	set brightness, range: 0 ~ 0x1F
0x21	[r1, g1, b1, 0, r2, g2, b2, 0]	set color palette
0x22	[vad_led]	set center LED: 0 - off, 1 - on, else - depends on VAD
0x23	[volume]	show volume, range: 0 ~ 12
0x24	[pattern]	set pattern, 0 - Google Home pattern, elf - Echo pattern

• VAD - Voice Activity Detection
• DOA - (Sound) Direction Of Arrival