海思NB-IOT模块HI2115芯片I2C通信

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        = ,
    FUNC_GPIO             = ,
    FUNC_UART0_TXD        = ,
    FUNC_UART0_TXIR       = ,
    FUNC_UART0_O2         = ,
    FUNC_UART0_O1         = ,
    FUNC_UART0_RTS        = ,
    FUNC_UART0_DTR        = ,
    FUNC_UART0_RXD        = ,
    FUNC_UART0_RXIR       = ,
    FUNC_UART0_CTS        = ,
    FUNC_UART0_DCD        = ,
    FUNC_UART0_DSR        = ,
    FUNC_UART0_RI         = ,
    FUNC_UART1_TXD        = ,
    FUNC_UART1_TXIR       = ,
    FUNC_UART1_O2         = ,
    FUNC_UART1_O1         = ,
    FUNC_UART1_RTS        = ,
    FUNC_UART1_DTR        = ,
    FUNC_UART1_RXD        = ,
    FUNC_UART1_RXIR       = ,
    FUNC_UART1_CTS        = ,
    FUNC_UART1_DCD        = ,
    FUNC_UART1_DSR        = ,
    FUNC_UART1_RI         = ,
    FUNC_LPUART_RXD       = ,
    FUNC_LPUART_TXD       = ,
    FUNC_DBG_CLK0         = ,
    FUNC_DBG_CLK1         = ,
    FUNC_DBG_CLK2         = ,
    FUNC_DBG_CLK3         = ,
    FUNC_RADIO_PIO        = ,
    FUNC_UICC_CLK         = ,
    FUNC_UICC_RST         = ,
    FUNC_UICC_IO          = ,
    FUNC_DSP_TMS          = ,
    FUNC_DSP_TDI          = ,
    FUNC_DSP_TDO          = ,
    FUNC_DSP_TRST         = ,
    FUNC_SPI_SCLK         = ,
    FUNC_SPI_CSB          = ,
    FUNC_SPI_UNIDIR_IN    = ,
    FUNC_SPI_UNIDIR_OUT   = ,
    FUNC_SPI_BIDIR_DATA0  = ,
    FUNC_SPI_BIDIR_DATA1  = ,
    FUNC_SPI_BIDIR_DATA2  = ,
    FUNC_SPI_BIDIR_DATA3  = ,
    FUNC_DSP_TCK          = ,
    FUNC_RADIO_RFFE_SCLK  = ,
    FUNC_RADIO_RFFE_SDATA = ,
    FUNC_PWM0             = ,
    FUNC_PWM0B            = ,
    FUNC_PWM1             = ,
    FUNC_PWM1B            = ,
    FUNC_SSP0TXD          = ,
    FUNC_SSP0RXD          = ,
    FUNC_SSP0TRX          = ,
    FUNC_SSP0CLK          = ,
    FUNC_SSP0FSS          = ,
    FUNC_SSP1TXD          = ,
    FUNC_SSP1RXD          = ,
    FUNC_SSP1TRX          = ,
    FUNC_SSP1CLK          = ,
    FUNC_SSP1FSS          = ,
    FUNC_I2C0_SDA         = ,
    FUNC_I2C0_SCL         = ,
    FUNC_I2C1_SDA         = ,
    FUNC_I2C1_SCL         = ,
    FUNC_UART2_TXD        = ,
    FUNC_UART2_TXIR       = ,
    FUNC_UART2_O2         = ,
    FUNC_UART2_O1         = ,
    FUNC_UART2_RTS        = ,
    FUNC_UART2_DTR        = ,
    FUNC_UART2_RXD        = ,
    FUNC_UART2_RXIR       = ,
    FUNC_UART2_CTS        = ,
    FUNC_UART2_DCD        = ,
    FUNC_UART2_DSR        = ,
    FUNC_UART2_RI         = ,
    FUNC_MAX              =     //!< 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