基于RT1170 支持EEPROM访问（五）

本文主要是通过迁移的思维，记录本人初次使用NXP MCUXpresso SDK API进行BSP开发

MCUXpresso SDK I2C API 接口链接
　　在MCUXpresso SDK 框架下提供了对I2C设备进行操作的接口。针对I2C当作输出使用，一般只需要设置I2C总线通讯的速率（如100khz或者400khz）。确认I2C设备的地址及其位数即可对I2C设置进行操作。从下面的截图可以看出来I2C总线可选择的时钟源以及其所对应的最大值。有助于对系统级别时钟初始化代码的理解。本文将使用MCUXpresso Config Tools v9来生成相关的代码。

1. 首先阅读原理图

　　设计I2C总线引脚，如下所示：
AT24C02_SCL----LPI2C6_SCL----GPIO1_LPSR_11
AT24C02_SDA----LPI2C6_SDA----GPIO1_LPSR_10

2. SDK api 应用

2.1 I2C 引脚配置

需要将对应的引脚复用I2C 功能引脚

生成的代码如下所示：

/*
 * TEXT BELOW IS USED AS SETTING FOR TOOLS *************************************
BOARD_InitLPI2C5Pins:
- options: {callFromInitBoot: 'true', coreID: cm7, enableClock: 'true'}
- pin_list:
  - {pin_num: R5, peripheral: LPI2C6, signal: SDA, pin_signal: GPIO_LPSR_10, pull_up_down_config: Pull_Down, pull_keeper_select: no_init, open_drain: Enable, drive_strength: Normal}
  - {pin_num: T5, peripheral: LPI2C6, signal: SCL, pin_signal: GPIO_LPSR_11, pull_keeper_select: no_init, open_drain: Enable, drive_strength: Normal}
 * BE CAREFUL MODIFYING THIS COMMENT - IT IS YAML SETTINGS FOR TOOLS ***********
 */

/* FUNCTION ************************************************************************************************************
 *
 * Function Name : BOARD_InitLPI2C5Pins, assigned for the Cortex-M7F core.
 * Description   : Configures pin routing and optionally pin electrical features.
 *
 * END ****************************************************************************************************************/
void BOARD_InitLPI2C5Pins(void) {
  CLOCK_EnableClock(kCLOCK_Iomuxc_Lpsr);      /* LPCG on: LPCG is ON. */

  IOMUXC_SetPinMux(
      IOMUXC_GPIO_LPSR_10_LPI2C6_SDA,         /* GPIO_LPSR_10 is configured as LPI2C6_SDA */
      0U);                                    /* Software Input On Field: Input Path is determined by functionality */
  IOMUXC_SetPinMux(
      IOMUXC_GPIO_LPSR_11_LPI2C6_SCL,         /* GPIO_LPSR_11 is configured as LPI2C6_SCL */
      0U);                                    /* Software Input On Field: Input Path is determined by functionality */
  IOMUXC_SetPinConfig(
      IOMUXC_GPIO_LPSR_10_LPI2C6_SDA,         /* GPIO_LPSR_10 PAD functional properties : */
      0x24U);                                 /* Slew Rate Field: Slow Slew Rate
                                                 Drive Strength Field: normal driver
                                                 Pull / Keep Select Field: Pull Enable
                                                 Pull Up / Down Config. Field: Weak pull down
                                                 Open Drain LPSR Field: Enabled
                                                 Domain write protection: Both cores are allowed
                                                 Domain write protection lock: Neither of DWP bits is locked */
  IOMUXC_SetPinConfig(
      IOMUXC_GPIO_LPSR_11_LPI2C6_SCL,         /* GPIO_LPSR_11 PAD functional properties : */
      0x20U);                                 /* Slew Rate Field: Slow Slew Rate
                                                 Drive Strength Field: normal driver
                                                 Pull / Keep Select Field: Pull Disable
                                                 Pull Up / Down Config. Field: Weak pull down
                                                 Open Drain LPSR Field: Enabled
                                                 Domain write protection: Both cores are allowed
                                                 Domain write protection lock: Neither of DWP bits is locked */
}

2.2 I2C 时钟配置

点击时钟模块可以看到LPI2C6时钟模块的根时钟为24Mhz,如下图所示：
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传

从上图可以很清楚地知道LPI2C6模块的时钟路径。
相关的初始化代码在clocl_config.c文件当中可以找到。

    /* Configure LPI2C6 using OSC_RC_48M_DIV2 */
    rootCfg.mux = kCLOCK_LPI2C6_ClockRoot_MuxOscRc48MDiv2;
    rootCfg.div = 1;
    CLOCK_SetRootClock(kCLOCK_Root_Lpi2c6, &rootCfg);