ICM20948 DMP代码详解（37）
接前一篇文章：ICM20948 DMP代码详解（36）
上一回开始分析icm20948_sensor_setup() ---> inv_icm20948_initialize_auxiliary函数 ---> inv_icm20948_set_slave_compass_id函数，解析了前两段代码，本回解析接下来的代码。为了便于理解和回顾，再次贴出该函数源码，在EMD-Core\sources\Invn\Devices\Drivers\ICM20948\Icm20948DataBaseDriver.c中，如下：
int inv_icm20948_set_slave_compass_id(struct inv_icm20948 *s, int id)
{
int result = 0;
(void)id;
//result = inv_icm20948_wakeup_mems(s);
//if (result)
//return result;
inv_icm20948_prevent_lpen_control(s);
activate_compass(s);
inv_icm20948_init_secondary(s);
// Set up the secondary I2C bus on 20630.
inv_icm20948_set_secondary(s);
//Setup Compass
result = inv_icm20948_setup_compass_akm(s);
//Setup Compass mounting matrix into DMP
result |= inv_icm20948_compass_dmp_cal(s, s->mounting_matrix, s->mounting_matrix_secondary_compass);
if (result)
desactivate_compass(s);
//result = inv_icm20948_sleep_mems(s);
inv_icm20948_allow_lpen_control(s);
return result;
}来到了以下代码片段：
inv_icm20948_init_secondary(s);
// Set up the secondary I2C bus on 20630.
inv_icm20948_set_secondary(s);3）inv_icm20948_init_secondary函数
inv_icm20948_init_secondary函数在EMD-Core\sources\Invn\Devices\Drivers\ICM20948\Icm20948AuxTransport.c中，代码如下：
void inv_icm20948_init_secondary(struct inv_icm20948 *s)
{
s->secondary_state.slv_reg[0].addr = REG_I2C_SLV0_ADDR;
s->secondary_state.slv_reg[0].reg = REG_I2C_SLV0_REG;
s->secondary_state.slv_reg[0].ctrl = REG_I2C_SLV0_CTRL;
s->secondary_state.slv_reg[0].d0 = REG_I2C_SLV0_DO;
s->secondary_state.slv_reg[1].addr = REG_I2C_SLV1_ADDR;
s->secondary_state.slv_reg[1].reg = REG_I2C_SLV1_REG;
s->secondary_state.slv_reg[1].ctrl = REG_I2C_SLV1_CTRL;
s->secondary_state.slv_reg[1].d0 = REG_I2C_SLV1_DO;
s->secondary_state.slv_reg[2].addr = REG_I2C_SLV2_ADDR;
s->secondary_state.slv_reg[2].reg = REG_I2C_SLV2_REG;
s->secondary_state.slv_reg[2].ctrl = REG_I2C_SLV2_CTRL;
s->secondary_state.slv_reg[2].d0 = REG_I2C_SLV2_DO;
s->secondary_state.slv_reg[3].addr = REG_I2C_SLV3_ADDR;
s->secondary_state.slv_reg[3].reg = REG_I2C_SLV3_REG;
s->secondary_state.slv_reg[3].ctrl = REG_I2C_SLV3_CTRL;
s->secondary_state.slv_reg[3].d0 = REG_I2C_SLV3_DO;
/* Make sure that by default all channels are disabled
To not inherit from a previous configuration from a previous run*/
inv_icm20948_secondary_stop_channel(s, 0);
inv_icm20948_secondary_stop_channel(s, 1);
inv_icm20948_secondary_stop_channel(s, 2);
inv_icm20948_secondary_stop_channel(s, 3);
}REG_I2C_SLV0_ADDR等相关的宏在EMD-Core\sources\Invn\Devices\Drivers\ICM20948\Icm20948Defs.h中，定义如下：
#define REG_I2C_SLV0_ADDR (BANK_3 | 0x03)
#define REG_I2C_SLV0_REG (BANK_3 | 0x04)
#define REG_I2C_SLV0_CTRL (BANK_3 | 0x05)
#define REG_I2C_SLV0_DO (BANK_3 | 0x06)
#define REG_I2C_SLV1_ADDR (BANK_3 | 0x07)
#define REG_I2C_SLV1_REG (BANK_3 | 0x08)
#define REG_I2C_SLV1_CTRL (BANK_3 | 0x09)
#define REG_I2C_SLV1_DO (BANK_3 | 0x0A)
#define REG_I2C_SLV2_ADDR (BANK_3 | 0x0B)
#define REG_I2C_SLV2_REG (BANK_3 | 0x0C)
#define REG_I2C_SLV2_CTRL (BANK_3 | 0x0D)
#define REG_I2C_SLV2_DO (BANK_3 | 0x0E)
#define REG_I2C_SLV3_ADDR (BANK_3 | 0x0F)
#define REG_I2C_SLV3_REG (BANK_3 | 0x10)
#define REG_I2C_SLV3_CTRL (BANK_3 | 0x11)
#define REG_I2C_SLV3_DO (BANK_3 | 0x12)
#define REG_I2C_SLV4_CTRL (BANK_3 | 0x15)对应ICM20948芯片手册中的以下内容：
这里I2C_SLV0~I2C_SLV3的各个寄存器都是一个意思，因此只以I2C_SLV0_XXX寄存器为例进行解析。
inv_icm20948_secondary_stop_channel函数在EMD-Core\sources\Invn\Devices\Drivers\ICM20948\Icm20948AuxTransport.c中，代码如下：
int inv_icm20948_secondary_stop_channel(struct inv_icm20948 *s, int index)
{
return inv_icm20948_write_single_mems_reg(s, s->secondary_state.slv_reg[index].ctrl, 0);
}s->secondary_state.slv_reg[index].ctrl对应的就是上边REG_I2C_SLVx_CTRL，把CTRL寄存器中的所有位都清零，也就是I2C_SLVx_EN、I2C_SLVx_BYTE_SW、I2C_SLVx_REG_SW、I2C_SLVx_GRP、I2C_SLVx_LENG[3:0]。
综合来看，inv_icm20948_init_secondary函数的功能正如其注释中所说：确保默认情况下禁用所有（I2C SLAVE）通道，不从上次运行的先前配置继承。
……
至此，inv_icm20948_init_secondary函数就解析完了。下一回继续后续内容的解析。
原文地址：https://blog.csdn.net/phmatthaus/article/details/142306413
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