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[ESP32]:基于esp-modbus实现serial主机
开发环境
- esp idf 5.1
- esp-modbus 1.0.13
使用如下指令添加组件,或者访问esp-modbus
idf.py add-dependency "espressif/esp-modbus^1.0.13"
Device parameters
对于master而言,需要理解的主要是device parameters,下面是一个parameters的例子
enum
{CID_INPUT = 0,CID_COIL,CID_HOLDING,
};const mb_parameter_descriptor_t device_parameters[] = {{CID_INPUT, (const char *)("INPUT"), (const char *)(""), 1, MB_PARAM_INPUT, 0x00, 5,INPUT_OFFSET(input_value1), PARAM_TYPE_U16, sizeof(uint16_t), OPTS(0, 0, 0), PAR_PERMS_READ_WRITE_TRIGGER},{CID_COIL, (const char *)("COIL"), (const char *)(""), 1, MB_PARAM_COIL, 0x00, 16,COIL_OFFSET(coil_value1), PARAM_TYPE_U8, sizeof(uint8_t), OPTS(0, 0, 0), PAR_PERMS_READ_WRITE_TRIGGER},{CID_HOLDING, (const char *)("HOLDING"), (const char *)(""), 1, MB_PARAM_HOLDING, 0x00, 5,HOLDING_OFFSET(holding_value1), PARAM_TYPE_U16, sizeof(uint16_t), OPTS(0, 0, 0), PAR_PERMS_READ_WRITE_TRIGGER},
};
可以看到,我们这边分别定义了输入寄存器、线圈与保持寄存器,其中,关于mb_parameter_descriptor_t的定义如下:
typedef struct {uint16_t cid; /*!< Characteristic cid */const char* param_key; /*!< The key (name) of the parameter */const char* param_units; /*!< The physical units of the parameter */uint8_t mb_slave_addr; /*!< Slave address of device in the Modbus segment */mb_param_type_t mb_param_type; /*!< Type of modbus parameter */uint16_t mb_reg_start; /*!< This is the Modbus register address. This is the 0 based value. */uint16_t mb_size; /*!< Size of mb parameter in registers */uint16_t param_offset; /*!< Parameter name (OFFSET in the parameter structure) */mb_descr_type_t param_type; /*!< Float, U8, U16, U32, ASCII, etc. */mb_descr_size_t param_size; /*!< Number of bytes in the parameter. */mb_parameter_opt_t param_opts; /*!< Parameter options used to check limits and etc. */mb_param_perms_t access; /*!< Access permissions based on mode */
} mb_parameter_descriptor_t;
其中:
- mb_size: 是你要读取的数量
- CID_INPUT这个parameters里,5就是要读取5个输入寄存器
- CID_COIL这个parameters里,16就是要读取16个线圈,注意,每一个线圈只有1个位
- param_size:是每一个数据的字节数
- CID_INPUT里,每一个数据的大小为2个字节,同时数据保存的类型也是uint16_t
- CID_COIL里,每一个数据的大小为1个字节,就是sizeof(uint8_t),但是我们上面写的是16个线圈,所以读取数据的时候要写两个uint8_t来存放结果
master读取
对于读取,只需要选择好device parameters里的cid即可,下面是一个读取线圈的例子
esp_err_t modbus_master_read_coil_reg()
{esp_err_t err = mbc_master_get_cid_info(CID_COIL, ¶m_descriptor);if ((err != ESP_ERR_NOT_FOUND) && (param_descriptor != NULL)){void *temp_data_ptr = master_get_param_data(param_descriptor);assert(temp_data_ptr);uint8_t type = 0;uint8_t value[2] = {0};err = mbc_master_get_parameter(CID_COIL, (char *)param_descriptor->param_key, (uint8_t *)&value, &type);if (err == ESP_OK){ESP_LOGI(TAG, "Coil: %d %d", (*(uint8_t *)&value[0]), *(uint8_t *)&value[1]);}}return err;
}
我们在刚才的device parameters里定义了要读16个线圈,返回的数据每一个是uint8_t,所以需要两个uint8_t的数据,所以我这里写一个数组。
实验效果如下:
127就是10000001
读取保持寄存与线圈的代码都差不多:
/*** @brief mdobus read input reg** @return esp_err_t*/
esp_err_t modbus_master_read_input_reg()
{esp_err_t err = mbc_master_get_cid_info(CID_INPUT, ¶m_descriptor);if ((err != ESP_ERR_NOT_FOUND) && (param_descriptor != NULL)){void *temp_data_ptr = master_get_param_data(param_descriptor);assert(temp_data_ptr);uint8_t type = 0;uint16_t value[5] = {0};err = mbc_master_get_parameter(CID_INPUT, (char *)param_descriptor->param_key, (uint8_t *)&value, &type);if (err == ESP_OK){ESP_LOGI(TAG, "Input: %d %d %d %d %d", value[0], value[1], value[2], value[3], value[4]);}}return err;
}/*** @brief modbus read holding reg** @return esp_err_t*/
esp_err_t modbus_master_read_holding_reg()
{esp_err_t err = mbc_master_get_cid_info(CID_HOLDING, ¶m_descriptor);if ((err != ESP_ERR_NOT_FOUND) && (param_descriptor != NULL)){void *temp_data_ptr = master_get_param_data(param_descriptor);assert(temp_data_ptr);uint8_t type = 0;uint16_t value[5] = {0};err = mbc_master_get_parameter(CID_HOLDING, (char *)param_descriptor->param_key, (uint8_t *)&value, &type);if (err == ESP_OK){ESP_LOGI(TAG, "Holding: %d %d %d %d %d", value[0], value[1], value[2], value[3], value[4]);}}return err;
}
完整代码参考:项目代码
Ref
modbus协议
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