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        = 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