1. 首先确定硬件上I2C的引脚，手册上并没有，海思技术支持说是14和15脚，我们用的是12和13脚，问题在于，如果是硬件I2C应该不能随便换个引脚吧，难道是模拟的时序？
2. 下一个奇怪的地方，这个寄存器居然只有两行，没其他地方使用，真奇怪？
看下相关的代码
3. PIO的设置
static I2C_RET i2c_set_pio(PIN pin, FUNC i2c_func) { if (pin != PIN_NONE) { if(!pio_set_function(pin, i2c_func)) { return I2C_RET_ERROR; } } }
继续往下看，最终设置的是下面的，还是直接写寄存器的意思？不过后面的半句话不太明白什么意思，意思是把这个数组放到外设的代码段里面。
/** * Direct access to register address space for all PIOs */
static volatile HAL_PIO_REGISTER_MAP hal_pio_registers[ PIN_MAX_NUMBER ] __attribute__((section(".peripherals")));
果然是对应寄存器的值
typedef struct { //lint -esym(754,HAL_PIO_REGISTER_MAP::*) Some of these aren't used directly.
uint32 pio_claim; //!< Peripheral claim register - register layout is different for a read compared to a write
uint32 pio_ctrl; //!< PIO_CTRL register
uint32 pio_irq_clr; //!< PIO_IRQ_CLR register
uint32 reserved_0; //!< Reserved
uint32 reserved_1; //!< Reserved
uint32 pio_ctrl_bitset; //!< PIO_CTRL_BITSET register
uint32 reserved_2; //!< Reserved
uint32 reserved_3; //!< Reserved
uint32 reserved_4; //!< Reserved
uint32 pio_ctrl_bitclr; //!< PIO_CTRL_BITCLR register
uint32 reserved_5; //!< Reserved
uint32 reserved_6; //!< Reserved
uint32 reserved_7; //!< Reserved
uint32 pio_ctrl_bittog; //!< PIO_CTRL_BITTOG register
uint32 reserved_8; //!< Reserved
uint32 reserved_9; //!< Reserved
} HAL_PIO_REGISTER_MAP;
看下FUNC的配置，这个应该是引脚复用图吧，难道每个引脚都可以随便作为任何功能？
typedef enum { FUNC_UNCLAIMED = 0, FUNC_GPIO = 1, FUNC_UART0_TXD = 2, FUNC_UART0_TXIR = 3, FUNC_UART0_O2 = 4, FUNC_UART0_O1 = 5, FUNC_UART0_RTS = 6, FUNC_UART0_DTR = 7, FUNC_UART0_RXD = 8, FUNC_UART0_RXIR = 9, FUNC_UART0_CTS = 10, FUNC_UART0_DCD = 11, FUNC_UART0_DSR = 12, FUNC_UART0_RI = 13, FUNC_UART1_TXD = 14, FUNC_UART1_TXIR = 15, FUNC_UART1_O2 = 16, FUNC_UART1_O1 = 17, FUNC_UART1_RTS = 18, FUNC_UART1_DTR = 19, FUNC_UART1_RXD = 20, FUNC_UART1_RXIR = 21, FUNC_UART1_CTS = 22, FUNC_UART1_DCD = 23, FUNC_UART1_DSR = 24, FUNC_UART1_RI = 25, FUNC_LPUART_RXD = 26, FUNC_LPUART_TXD = 27, FUNC_DBG_CLK0 = 112, FUNC_DBG_CLK1 = 113, FUNC_DBG_CLK2 = 114, FUNC_DBG_CLK3 = 115, FUNC_RADIO_PIO = 128, FUNC_UICC_CLK = 129, FUNC_UICC_RST = 130, FUNC_UICC_IO = 131, FUNC_DSP_TMS = 132, FUNC_DSP_TDI = 133, FUNC_DSP_TDO = 134, FUNC_DSP_TRST = 135, FUNC_SPI_SCLK = 136, FUNC_SPI_CSB = 137, FUNC_SPI_UNIDIR_IN = 138, FUNC_SPI_UNIDIR_OUT = 139, FUNC_SPI_BIDIR_DATA0 = 140, FUNC_SPI_BIDIR_DATA1 = 141, FUNC_SPI_BIDIR_DATA2 = 142, FUNC_SPI_BIDIR_DATA3 = 143, FUNC_DSP_TCK = 144, FUNC_RADIO_RFFE_SCLK = 145, FUNC_RADIO_RFFE_SDATA = 146, FUNC_PWM0 = 192, FUNC_PWM0B = 193, FUNC_PWM1 = 194, FUNC_PWM1B = 195, FUNC_SSP0TXD = 196, FUNC_SSP0RXD = 197, FUNC_SSP0TRX = 198, FUNC_SSP0CLK = 199, FUNC_SSP0FSS = 200, FUNC_SSP1TXD = 201, FUNC_SSP1RXD = 202, FUNC_SSP1TRX = 203, FUNC_SSP1CLK = 204, FUNC_SSP1FSS = 205, FUNC_I2C0_SDA = 206, FUNC_I2C0_SCL = 207, FUNC_I2C1_SDA = 208, FUNC_I2C1_SCL = 209, FUNC_UART2_TXD = 210, FUNC_UART2_TXIR = 211, FUNC_UART2_O2 = 212, FUNC_UART2_O1 = 213, FUNC_UART2_RTS = 214, FUNC_UART2_DTR = 215, FUNC_UART2_RXD = 216, FUNC_UART2_RXIR = 217, FUNC_UART2_CTS = 218, FUNC_UART2_DCD = 219, FUNC_UART2_DSR = 220, FUNC_UART2_RI = 221, FUNC_MAX = 222 //!< Limit to range of valid values
} FUNC;
芯片的数据手册，这样说起来，这24个PIO可以复用到任何的外设上。现在问题是一共有40个PIO，说的是那24个PIO?
4. 说是PIO分为4个区域，每个区域的电压似乎可以不一样
