Chapter 2. API Reference
(continued from previous page)
0, PARAM_TYPE_FLOAT, 4, OPTS( 20, 30, 1 ), PAR_PERMS_READ_
,→WRITE_TRIGGER },
};
// Calculate number of parameters in the table
uint16_t num_device_parameters = (sizeof(device_parameters) / sizeof(device_
,→parameters[0]));
During initialization of the Modbus stack, a pointer to the Data Dictionary (called descriptor) must be provided as
the parameter of the function below.
mbc_master_set_descriptor(): Initialization of master descriptor.
ESP_ERROR_CHECK(mbc_master_set_descriptor(&device_parameters[0], num_device_
,→parameters));
The Data Dictionary can be initialized from SD card, MQTT or other source before start of stack. Once the initial-
ization and setup is done, the Modbus controller allows the reading of complex parameters from any slave included
in descriptor table using its CID.
Master Communication Options Calling the setup function allows for specific communication options to be de-
fined for port.
mbc_master_setup()
The communication structure provided as a parameter is different for serial and TCP communication mode.
Example setup for serial port:
mb_communication_info_t comm_info = {
.port = MB_PORT_NUM, // Serial port number
.mode = MB_MODE_RTU, // Modbus mode of communication (MB_MODE_RTU or MB_
,→MODE_ASCII)
.baudrate = 9600, // Modbus communication baud rate
.parity = MB_PARITY_NONE // parity option for serial port
};
ESP_ERROR_CHECK(mbc_master_setup((void*)&comm_info));
Modbus master TCP port requires additional definition of IP address table where number of addresses should be
equal to number of unique slave addresses in master Modbus Data Dictionary:
The order of IP address string corresponds to short slave address in the Data Dictionary.
#define MB_SLAVE_COUNT 2 // Number of slaves in the segment being accessed (as␣
,
→
defined in Data Dictionary)
char* slave_ip_address_table[MB_SLAVE_COUNT] = {
"192.168.1.2", // Address corresponds to UID1 and set to predefined value␣
,→by user
"192.168.1.3", // corresponds to UID2 in the segment
NULL // end of table
};
mb_communication_info_t comm_info = {
.ip_port = MB_TCP_PORT, // Modbus TCP port number (default␣
,→= 502)
.ip_addr_type = MB_IPV4, // version of IP protocol
.ip_mode = MB_MODE_TCP, // Port communication mode
.ip_addr = (void*)slave_ip_address_table, // assign table of IP addresses
.ip_netif_ptr = esp_netif_ptr // esp_netif_ptr pointer to the␣
,→corresponding network interface
(continues on next page)
Espressif Systems 626
Submit Document Feedback
Release v4.4
To Next Page
Loading...