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53 lines
2.7 KiB
C
53 lines
2.7 KiB
C
#pragma once
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#include "net.h"
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// Modbus TCP function codes passed in mg_modbus_req.func.
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#define MG_MODBUS_FUNC_READ_COILS 1 // Read 1-2000 discrete output coils
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#define MG_MODBUS_FUNC_READ_DISCRETE_INPUTS 2 // Read 1-2000 discrete input coils
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#define MG_MODBUS_FUNC_READ_HOLDING_REGISTERS 3 // Read 1-125 holding registers
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#define MG_MODBUS_FUNC_READ_INPUT_REGISTERS 4 // Read 1-125 input registers
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#define MG_MODBUS_FUNC_WRITE_SINGLE_COIL 5 // Write one output coil
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#define MG_MODBUS_FUNC_WRITE_SINGLE_REGISTER 6 // Write one holding register
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#define MG_MODBUS_FUNC_WRITE_MULTIPLE_COILS 15 // Write 1-1968 output coils
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#define MG_MODBUS_FUNC_WRITE_MULTIPLE_REGISTERS 16 // Write 1-123 holding registers
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// Standard Modbus exception codes. Set mg_modbus_req.error to one of these
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// in the MG_EV_MODBUS_REQ handler to return an exception response to the client.
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#define MG_MODBUS_ERR_NONE 0 // No error; send a normal response
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#define MG_MODBUS_ERR_ILLEGAL_FUNCTION 1 // Function code not supported
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#define MG_MODBUS_ERR_ILLEGAL_ADDRESS 2 // Starting address or range out of bounds
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#define MG_MODBUS_ERR_ILLEGAL_VALUE 3 // Data value not accepted
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#define MG_MODBUS_ERR_DEVICE_FAILURE 4 // Unrecoverable device error
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// Modbus request passed as ev_data to the MG_EV_MODBUS_REQ event handler.
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//
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// For READ functions (READ_COILS, READ_DISCRETE_INPUTS, READ_HOLDING_REGISTERS,
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// READ_INPUT_REGISTERS): u.bits / u.regs points to a zeroed, heap-allocated
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// array of len entries. The handler fills in the values to return.
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//
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// For WRITE functions: u.bits / u.regs is pre-populated from the client
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// request. len=1 for single-write functions.
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//
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// Do NOT free u.bits or u.regs - the library frees them after the handler
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// returns and the response has been sent.
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//
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// Set error to a non-zero MG_MODBUS_ERR_* code to send an exception response
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// instead of a data response. The response is sent automatically on return.
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struct mg_modbus_req {
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uint8_t func; // Function code, one of MG_MODBUS_FUNC_*
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uint8_t error; // Exception code; set to MG_MODBUS_ERR_* to return an error
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uint16_t addr; // Starting coil/register address from the request
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union {
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bool *bits; // Coil values; used by coil function codes
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uint16_t *regs; // Register values; used by register function codes
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} u;
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uint16_t len; // Number of entries in u.bits or u.regs
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};
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// Creates a Modbus TCP listener on url. Fires MG_EV_MODBUS_REQ for each
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// complete request; ev_data is struct mg_modbus_req *. Returns the listening
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// connection, or NULL on error.
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struct mg_connection *mg_modbus_listen(struct mg_mgr *mgr, const char *url,
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mg_event_handler_t fn, void *fn_data);
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