pi-ds4-dongle

ds4蓝牙逆向工程：DS4-BT

ds4drv关于蓝牙音频传输的讨论：chrippa/ds4drv

ds4映射NintendoSwitch键位

较新的linux驱动中已经集成了ds4驱动，源码位置：

linux/drivers/hid/hid-sony.c

这里直接读取了linux准备好的/dev/input/js*设备，或者按照逆向工程读取report_id 11的内容。

ds4的震动、LED与其他功能

TBD

ds4传输蓝牙音频

bluez与SBC编码

按照逆向工程的描述，ds4接收的是SBC编码的蓝牙音频，作为linux默认的蓝牙协议栈，bluez提供了SBC编解码API。

pi0的Debian系统可以直接apt安装

# apt install libsbc-dev

请阅读bluez提供的例子，理解一下SBC编码原理与使用方法。

对于ds4来说，SBC音频头如下：

9c 75 19 24

 0x9c = 156 syncword (always set to 156)
 1 byte - sf bl cm a s (msb..lsb)
   * frequency:
       00-16000
       01-32000
       10-44100
       11-48000
   * blocks:
       00-4
       01-8
       10-12
       11-16
   * channels:
       00-MONO
       01-DUAL_CHANNEL 
       10-STEREO 
       11-JOINT_STEREO
   * allocation method:
       0-loudnes
       1-SNR
   * subbands:
       0-4
       1-8
 1 byte - bitpool
       ...

在例子中选择的SBC编码是32kHz, 16blocks, 2channels, loudness, 8subbands,使用sbc_encode(...)时会生成对应音频头.

定时发送

用于使用的是hidraw传输数据，我们要自行规划每次数据的传输间隔，保证在上一包音频数据消耗完时有下一包音频数据补充上。

对于"32kHz 8subbands"SBC编码后的数据来说，每一帧大小为：

frame_size = 4 + (4 * subbands * channels) / 8 +(blocks * channels * bitpool) / 8

= 4 + 4*8*2/8 + 16*2*25/8 = 112bytes

每帧时间为：

frame_time = subbands * blocks / sample_rate

= 8*16/32 = 4ms

report_14/15每包有2帧数据，耗时8ms；report_17/18/19每包有4帧数据，耗时16ms。理论上，我们只要每8ms或16ms发送一包数据即可。
ALSA与PCM

在较新的linux内核中使用ALSA作为默认的音频框架，我们需要从ALSA读取PCM数据再交由SBC编码，最后通过蓝牙发送ds4。

这里使用libasound2读写声卡设备：
```
# apt install libasound2-dev
```
需要注意的是，通过snd_pcm_hw_params_get_period_size获取的PCM的帧数量，需要换算成字节数：

frame_size = sample_bits * channels / 8
period_size = period_frames * frame_size

对于SND_PCM_FORMAT_S16_BE双声道来说，每一帧大小为4bytes，SBC每帧大小为sbc_get_codesize(...)=512bytes,编码后大小为sbc_encode(...)=112bytes,与ds4逆向工程提供的数据一致。

Sample

设置pi0的UAC

pi0的Debian系统内核使用的是UAC2.0，如果需要连接Nintendo Switch作为USB音箱的话，需要编译成UAC1.0，请参考我的另一个项目pi-joystick。

设置pi0的audio source

# pacmd list-sources

> index: 1
  	name: <alsa_input.platform-20980000.usb.analog-stereo>
  	driver: <module-alsa-card.c>
  	flags: HARDWARE DECIBEL_VOLUME LATENCY DYNAMIC_LATENCY
  	state: IDLE
  	suspend cause: 
  	priority: 9009
  	volume: front-left: 65536 / 100% / 0.00 dB,   front-right: 65536 / 100% / 0.00 dB
  	        balance 0.00
  	base volume: 65536 / 100% / 0.00 dB
  	volume steps: 65537
  	muted: no
  	current latency: 3945.43 ms
  	max rewind: 0 KiB
  	sample spec: s16le 2ch 48000Hz
  	channel map: front-left,front-right
  	             Stereo
  	used by: 0
  	linked by: 0
  	configured latency: 341.33 ms; range is 0.50 .. 341.33 ms
  	card: 0 <alsa_card.platform-20980000.usb>
  	module: 6
  	properties:
  		alsa.resolution_bits = "16"
  		device.api = "alsa"
  		device.class = "sound"
  		alsa.class = "generic"
  		alsa.subclass = "generic-mix"
  		alsa.name = "UAC2 PCM"
  		alsa.id = "UAC2 PCM"
  		alsa.subdevice = "0"
  		alsa.subdevice_name = "subdevice #0"
  		alsa.device = "0"
  		alsa.card = "1"
  		alsa.card_name = "UAC2_Gadget"
  		alsa.long_card_name = "UAC2_Gadget 0"
  		device.bus_path = "platform-20980000.usb"
  		sysfs.path = "/devices/platform/soc/20980000.usb/gadget/sound/card1"
  		device.string = "hw:1"
  		device.buffering.buffer_size = "65536"
  		device.buffering.fragment_size = "4096"
  		device.access_mode = "mmap+timer"
  		device.profile.name = "analog-stereo"
  		device.profile.description = "Analog Stereo"
  		device.description = "UAC2_Gadget Analog Stereo"
  		module-udev-detect.discovered = "1"
  		device.icon_name = "audio-card"
  	ports:
  		analog-input: Analog Input (priority 10000, latency offset 0 usec, available: unknown)
  			properties:
  				
  	active port: <analog-input>

看到pi0 gadget模拟的音频输入设备为index: 1 , name: <alsa_input.platform-20980000.usb.analog-stereo>，接下来把它设置为默认信源。

# pacmd set-default-source 1

pi0蓝牙连接ds4

推荐编译安装最新的bluez，较老的版本可能会出现一些莫名的错误。

# bluetoothctl -v
> 5.9

# bluetoothctl 
[bluetooth]# power on
[bluetooth]# agent on
[bluetooth]# default-agent
[bluetooth]# scan on
Discovery started
[CHG] Controller B8:27:**:**:**:** Discovering: yes
[NEW] Device DC:0C:**:**:**:** Wireless Controller
[bluetooth]# info DC:0C:**:**:**:** 
Device DC:0C:**:**:**:**
	Name: Wireless Controller
	Alias: Wireless Controller
	Class: 0x002508
	Icon: input-gaming
	Paired: yes
	Trusted: yes
	Blocked: no
	Connected: no
	LegacyPairing: no
	UUID: Human Interface Device... (00001124-0000-1000-8000-00805f9b34fb)
	UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
	Modalias: usb:v054Cp09CCd0100
[bluetooth]# pair DC:0C:**:**:**:**
Attempting to pair with DC:0C:**:**:**:**
[CHG] Device DC:0C:**:**:**:** Connected: yes
[CHG] Device DC:0C:**:**:**:** Modalias: usb:v054Cp09CCd0100
[CHG] Device DC:0C:**:**:**:** Modalias: usb:v054Cp09CCd0100
[CHG] Device DC:0C:**:**:**:** UUIDs has unsupported type
[CHG] Device DC:0C:**:**:**:** Paired: yes
Pairing successful
[CHG] Device DC:0C:**:**:**:** Connected: no
[CHG] Device DC:0C:**:**:**:** RSSI: -43
[bluetooth]# yes
[bluetooth]# connet DC:0C:**:**:**:**
Attempting to connect to DC:0C:**:**:**:**
[CHG] Device DC:0C:**:**:**:** Connected: yes
Connection successful
[CHG] Device DC:0C:**:**:**:** Modalias: usb:v054Cp09CCd0100
[CHG] Device DC:0C:**:**:**:** Modalias: usb:v054Cp09CCd0100

成功连接ds4后，ds4手柄会亮起蓝色氛围灯，pi0中新增hidraw设备。

# ls -al /dev/hidraw*
> crw------- 1 root root 247, 0 4月   6 12:54 /dev/hidraw0
# chmod 666 /dev/hidraw0

如果出现了什么问题，请考虑升级bluez。

?

TBD

mumumusuc/pi-ds4-dongle

pi-ds4-dongle

ds4映射NintendoSwitch键位

ds4的震动、LED与其他功能

ds4传输蓝牙音频

Sample