问：我在STM32F767里面看到有如下描述，想确认下，在767的SAI里面，是属于全双工还是半双工？ Serial audio interface (SAI) The devices embed two serial audio interfaces. The serial audio interface is based on two independent audio subblocks which can operate as transmitter or receiver with their FIFO. Many audio protocols are supported by each block: I2S standards, LSB or MSB-justified, PCM/DSP, TDM, AC’97 and SPDIF output, supporting audio sampling frequencies from 8 kHz up to 192 kHz. Both subblocks can be configured in master or in slave mode. In master mode, the master clock can be output to the external DAC/CODEC at 256 times of the sampling frequency. The two sub-blocks can be configured in synchronous mode when full-duplex mode is required.
问：STM32F4的技术参考手册中P276/8.3.3节，有一段话 GPIOx_OSPEEDR registers are used to select speed (the I/O speed pins are directly connected to the corresponding GPIOx_OSPEEDR register bits whatever the I/O direction)，这段话的意思是 速度寄存器GPIOx_OSPEEDR与端口方向无关，除了可以配置输出的速度，也可以配置输入，AF及模拟的速度吗？
问：我用IAR 7.8编译STM32 PMSM FOC SDK 4.30 自带的示例工程总是报错, 不知道原因: Fatal Error[Pe035]: #error directive: "Compiler generates FPU instructions for a device without an FPU (check __FPU_PRESENT)" C:\Program Files (x86)\IAR Systems\Embedded Workbench 7.5\arm\CMSIS\Include\core_cm4.h 115 请前辈赐教。