USB Control Protocol

With the USB 4 mic array, we can tune some parameters of its audio processing algorithms or get the Direction Of Arrival (DOA). These data exchanges are done through a USB Vendor Specific Class Interface. The interface can be accessed through USB Control Transfer.

On Linux, we can run lsusb -v -d 2886: to find the interface:

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 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,
        id,
        data,
        TIMEOUT)

We only need to care about id, command and data:

bit	7	6	5-0
command	1:read, 0:write	1: int, 0:float	cmd

name	id	cmd	type	max	min	r/w	note
AECFREEZEONOFF	18	7	int	1	0	rw	Adaptive Echo Canceler updates inhibit, 0 = Adaptation enabled, 1 = Freeze adaptation, filter only
AECNORM	18	19	float	16	0.25	rw	Limit on norm of AEC filter coefficients
AECPATHCHANGE	18	25	int	1	0	ro	AEC Path Change Detection, 0 = false (no path change detected), 1 = true (path change detected)
RT60	18	26	float	0.9	0.25	ro	Current RT60 estimate in seconds
HPFONOFF	18	27	int	3	0	rw	High-pass Filter on microphone signals, 0 = OFF, 1 = ON - 70 Hz cut-off, 2 = ON - 125 Hz cut-off, 3 = ON - 180 Hz cut-off
RT60ONOFF	18	28	int	1	0	rw	RT60 Estimation for AES. 0 = OFF 1 = ON
AECSILENCELEVEL	18	30	float	1	1e-09	rw	Threshold for signal detection in AEC [-inf .. 0] dBov (Default: -80dBov = 10log10(1x10-8))
AECSILENCEMODE	18	31	int	1	0	ro	AEC far-end silence detection status, 0 = false (signal detected) , 1 = true (silence detected)
AGCONOFF	19	0	int	1	0	rw	Automatic Gain Control, 0 = OFF , 1 = ON
AGCMAXGAIN	19	1	float	1000	1	rw	Maximum AGC gain factor, [0 .. 60] dB (default 30dB = 20log10(31.6))
AGCDESIREDLEVEL	19	2	float	0.99	1e-08	rw	Target power level of the output signal, [−inf .. 0] dBov (default: −23dBov = 10log10(0.005))
AGCGAIN	19	3	float	1000	1	rw	Current AGC gain factor, [0 .. 60] dB (default: 0.0dB = 20log10(1.0))
AGCTIME	19	4	float	1	0.1	rw	Ramps-up / down time-constant in seconds.
CNIONOFF	19	5	int	1	0	rw	Comfort Noise Insertion, 0 = OFF, 1 = ON
FREEZEONOFF	19	6	int	1	0	rw	Adaptive beamformer updates, 0 = Adaptation enabled, 1 = Freeze adaptation, filter only
STATNOISEONOFF	19	8	int	1	0	rw	Stationary noise suppression, 0 = OFF, 1 = ON
GAMMA_NS	19	9	float	3	0	rw	Over-subtraction factor of stationary noise. min .. max attenuation
MIN_NS	19	10	float	1	0	rw	Gain-floor for stationary noise suppression, [−inf .. 0] dB (default: −16dB = 20log10(0.15))
NONSTATNOISEONOFF	19	11	int	1	0	rw	Non-stationary noise suppression, 0 = OFF, 1 = ON
GAMMA_NN	19	12	float	3	0	rw	Over-subtraction factor of non- stationary noise. min .. max attenuation
MIN_NN	19	13	float	1	0	rw	Gain-floor for non-stationary noise suppression, [−inf .. 0] dB (default: −10dB = 20log10(0.3))
ECHOONOFF	19	14	int	1	0	rw	Echo suppression, 0 = OFF, 1 = ON
GAMMA_E	19	15	float	3	0	rw	Over-subtraction factor of echo (direct and early components). min .. max attenuation
GAMMA_ETAIL	19	16	float	3	0	rw	Over-subtraction factor of echo (tail components). min .. max attenuation
GAMMA_ENL	19	17	float	5	0	rw	Over-subtraction factor of non-linear echo. min .. max attenuation
NLATTENONOFF	19	18	int	1	0	rw	Non-Linear echo attenuation, 0 = OFF, 1 = ON
NLAEC_MODE	19	20	int	2	0	rw	Non-Linear AEC training mode, 0 = OFF, 1 = ON - phase 1, 2 = ON - phase 2
SPEECHDETECTED	19	22	int	1	0	ro	Speech detection status, 0 = false (no speech detected), 1 = true (speech detected)
FSBUPDATED	19	23	int	1	0	ro	FSB Update Decision, 0 = false (FSB was not updated), 1 = true (FSB was updated)
FSBPATHCHANGE	19	24	int	1	0	ro	FSB Path Change Detection, 0 = false (no path change detected), 1 = true (path change detected)
TRANSIENTONOFF	19	29	int	1	0	rw	Transient echo suppression, 0 = OFF, 1 = ON
VOICEACTIVITY	19	32	int	1	0	ro	VAD voice activity status, 0 = false (no voice activity), 1 = true (voice activity)
STATNOISEONOFF_SR	19	33	int	1	0	rw	Stationary noise suppression for ASR, 0 = OFF, 1 = ON
NONSTATNOISEONOFF_SR	19	34	int	1	0	rw	Non-stationary noise suppression for ASR, 0 = OFF, 1 = ON
GAMMA_NS_SR	19	35	float	3	0	rw	Over-subtraction factor of stationary noise for ASR, [0.0 .. 3.0] (default: 1.0)
GAMMA_NN_SR	19	36	float	3	0	rw	Over-subtraction factor of non-stationary noise for ASR, [0.0 .. 3.0] (default: 1.1)
MIN_NS_SR	19	37	float	1	0	rw	Gain-floor for stationary noise suppression for ASR, [−inf .. 0] dB (default: −16dB = 20log10(0.15))
MIN_NN_SR	19	38	float	1	0	rw	Gain-floor for non-stationary noise suppression for ASR, [−inf .. 0] dB (default: −10dB = 20log10(0.3))
GAMMAVAD_SR	19	39	float	1000	0	rw	Set the threshold for voice activity detection, [−inf .. 60] dB (default: 3.5dB 20log10(1.5))
DOAANGLE	21	0	int	359	0	ro	DOA angle. Current value. Orientation depends on build configuration.