[Modbus]
描述
Reads the Holding Registers register.
語法
node1.readHoldingRegister(address)
node2.readHoldingRegister(address, size, buffer)
參數
node1/node2: ModbusSlaveNode object.address: Address of the Holding Registers to be read.size: The number of Holding Registers to be read.buffer: Copy the read-out Holding Registers data to the array space pointed to by the buffer.
回傳
int: The HoldingRegister location data is returned when only the address pointer is used.
If the specified buffer is used, MODBUS_SUCCESS is returned, and EXCEPTION_CODE is returned.
範例
#include <Modbus86.h>
ModbusSlave bus;
ModbusSlaveNode node;
uint32_t command = 0;
uint32_t lasttime = 0;
uint8_t read_holding_registers( uint8_t function,
uint16_t address,
uint16_t length)
{
for (int i = address; i < address + length; i++) {
if (i == 16)
node.writeHoldingRegister(i, command & 0xFFFF);
else if (i == 17)
node.writeHoldingRegister(i, (command >> 16) & 0xFFFF);
}
return MODBUS_SUCCESS;
}
uint8_t write_multiple_registers( uint8_t function,
uint16_t address,
uint16_t length)
{
int i;
for (i = address; i < address + length; i++) {
if (i == 16)
command = (command & 0xFFFF0000) | node.readHoldingRegister(i);
else if (i == 17)
command =
(command & 0x0000FFFF) | (node.readHoldingRegister(i) << 16);
}
return MODBUS_SUCCESS;
}
void setup()
{
Serial485.begin(115200);
/* Modbus RTU Mode via RS485. */
bus.begin(MODBUS_RTU, Serial485);
/* Slave node with ID 11. */
node.attach(11, bus);
/* Set the callback function of Read Holding Registers (0x03). */
node.cbFunc[MODBUS_CB_READ_HOLDING_REGISTERS]
= read_holding_registers;
/* Set the callback function of Write Multiple Registers (0x10). */
node.cbFunc[MODBUS_CB_WRITE_MULTIPLE_REGISTERS]
= write_multiple_registers;
}
void loop()
{
uint32_t now;
node.poll();
now = millis();
if (now - lasttime > 500) {
lasttime = now;
Serial.print("commnad = ");
Serial.println(command);
}
}也可以看看
函式庫參考主頁面
86Duino 參考的文本是根據 Creative Commons Attribution-ShareAlike 3.0 License，部分文本是從 the Arduino reference 修改的。 參考中的代碼示例已發佈到公共領域。
