====== ImodbusRTUmaster() ======

''ImodbusRTUmaster()'' executes a single Master request immediately.

{{:en-us_commands:reference:imodbusrtumaster.svg?900|ImodbusRTUmaster command operation flow}}

''uint8_t ImodbusRTUmaster(HardwareSerial& serialPort, uint8_t slaveId, uint8_t functionCode, uint16_t address, uint16_t quantity, uint16_t* data, uint16_t timeoutMs = 100)''

===== Commands =====

^ Command ^ Arguments ^ Return Value ^ Operation ^
| ''ImodbusRTUmaster(serialPort, slaveId, functionCode, address, quantity, data, timeoutMs)'' | ''HardwareSerial& serialPort'' — Serial port connected to RS-485\\ ''uint8_t slaveId'' — Slave address\\ ''uint8_t functionCode''\\ ''uint16_t address''\\ ''uint16_t quantity''\\ ''uint16_t* data''\\ ''uint16_t timeoutMs = 100'' | ''uint8_t'' | Executes a single Master request immediately. |


===== Example =====

<code cpp>
uint16_t data[10];
uint16_t readValue0;
uint16_t readValue1;

void setup() {
  ImodbusRTUmasterInit(Serial2, 9600);  // Set the Master's communication port and baud rate.
}

void loop() {
  uint8_t result;

  result = ImodbusRTUmaster(Serial2, 1, 0x03, 0, 2, data);  // Execute a single Master request immediately.
  if (result == IMODBUS_RTU_SUCCESS) {
    readValue0 = data[0];
    readValue1 = data[1];
  }

  data[0] = 1234;
  ImodbusRTUmaster(Serial2, 1, 0x06, 10, 1, data);  // Execute a single Master request immediately.
}
</code>

===== Precautions =====

  * Keep calling the Slave or Master execution function in ''loop()''.
  * The data array size must be at least the requested quantity.
  * Do not treat return codes BUSY and IDLE as communication failures.
  * When sharing ''M'' and ''D'' with Cnet/MC Protocol, define a single final size and initialization order. Do not call ''ImodbusRTUMem()'' or ''ICnetMem()'' again at runtime.
  * Memory allocation functions do not return success status. For nonzero sizes, verify that ''M'' and ''D'' are not ''nullptr'' before accessing them in user code.

===== Built-in Commands in the Same Category =====

  * [[:en-us_commands:reference:imodbusrtumasterinit|ImodbusRTUmasterInit() View detailed description]]
  * [[:en-us_commands:reference:imodbusrtumasteradd|ImodbusRTUmasterAdd() View detailed description]]
  * [[:en-us_commands:reference:imodbusrtumasterrun|ImodbusRTUmasterRun() View detailed description]]

[[:en-us_commands:builtin|← Built-in Command List]]