•前馈ANC：
•在理想情况下可以实现高噪声降低
•与反馈ANC相比，对拟合更敏感
•每个ANC耳机使用一个数字硬件滤波器
•反馈ANC：
•需要硬件滤波器以避免Rx信号失真
•如果调整不当，可能会出现稳定性问题
•与前馈ANC相比，在降低低频方面更有效
•每个ANC耳机使用两个数字硬件滤波器
•混合ANC：
•前馈+反馈。 两全其美
•每个ANC耳机使用三个数字硬件滤波器
•Peak attenuation -30dB
•Spectrum of attenuation 70Hz to 2kHz (-10dB or more)
Latency
•Baseline latency of 7-10 usecthrough the ANC hardware
AudioAncStreamEnable(en0, en1) for each instance of ANC. It uses bitfields to specify which ANC paths are enabled/disabled
Changing filters
–ANC tuning capability allows different ANC parameter or filter sets to be downloaded to the chip or saved to a file using different UCID’s (Use-case ID’s).
–Filter sets are generated using QACT.
–Filters stored in audio user keys in apps SPI flash.
–Command from applications processor to filesystem to retrieve ANC parameters
•Application libraries
•<ADK path>\apps\libs\anc
•<ADK path>\apps\libs\audio_anc_tuning
•User PS filesystem: Parameter Storage
•<ADK path> \apps\applications\sink\qcc512x_qcc302x\common\anc_tuning_config.htf
•Customer RO filesystem: Download ANC tuning
•Prebuilt EDKCS: <ADK path> \audio\kalimba_ROM_4786\kymera\prebuilt_dkcs\aura_rom_v02_release
•Source Code:<ADK path>\audio\kalimba\kymera\capabilities\anc_tuning
•QACT workspace: <ADK path> \audio\kalimba\kymera\output\aura_rom_v02_release\QACT
?ANC allows gains, coefficients to be written to the hardware using a double banking scheme and gain changes on zero crossing
Bluetooth RF testing
Device Under Test (DUT).
Entering BR/EDR test mode
BR/EDR test mode can be entered in either of the two ways:
■ From the on chip application:
The connection library function ConnectionEnterDutMode can be used to enter DUT mode from a customer application. The ADK sink application implements an event (EventUsrEnterDutMode) which can be used to enter DUT mode based on a mode/button combination.
■ Using BlueTest3:
1. Connect to the device under test using the USB Debug or TRB, selecting the required transport
Entering Bluetooth Low Energy Direct Test Mode
To enter Bluetooth Low Energy Test Mode:
1. Expose an H4 UART HCI interface.
To do this, the Bluetooth subsystem must not be initialized by the on chip application. For this purpose, a minimal application that does not initialize the connection library (and hence Bluetooth subsystem) can be used.
Another option is to add a mode to the ADK sink application in which no call is made to sinkConnectionInit() at boot time.
2. Modify the UartPinsConfig MIB Key in the appropriate subsys0_config2.htf curator configuration file, which is located in the cur_cfg_filesystem directory, to select the PIOs that the UART should be multiplexed to.
NOTE: The format of this is key is [RTS_PIO, CTS_PIO, TX_PIO, RX_PIO]. If pins are not required (for example, if hardware flow control is not being used) they can be assigned the value 0x80.
3. Set the following PS Keys for the Bluetooth subsystem by editing the subsys1_config1.htf file, which is located in the fw_cfg_filesystem folder:
□ PSKEY_HOST_INTERFACE = 3 (for H4 UART)
□ PSKEY_UART_CONFIG_H4 = 0x8a0 (for parity = none, flow control = none)
□ PSKEY_UART_BITRATE = 9600 (optional, if not set the default bit rate is 115200)
NOTE: The UART config and bit rate can be customized if necessary, but must match those configured on the Bluetooth Test Set.
4. Build and deploy the configuration files (and application if necessary) to the device.
5. Start the Bluetooth subsystem by issuing the command, in the pydbg command line:
cur.fw.cucmd.start_bt_hci_service()
6. The Bluetooth HCI interface is now exposed on the selected PIOs allowing Bluetooth Low Energy tests to be performed using the Bluetooth Test Set.
dBFS的全称为Decibels Full Scale