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| 1 | +/* |
| 2 | + Modbus RTU Client Parameters |
| 3 | +
|
| 4 | + This sketch is the same as ModbusRTUClientToggle and shows how to set |
| 5 | + a few RS485 parameters. |
| 6 | +
|
| 7 | + Circuit: |
| 8 | + - Arduino Opta |
| 9 | + - GND connected to GND of the Modbus RTU server |
| 10 | + - A(-) connected to A of the Modbus RTU server |
| 11 | + - B(+) connected to B of the Modbus RTU server |
| 12 | +*/ |
| 13 | + |
| 14 | +#include <ArduinoRS485.h> // ArduinoModbus depends on the ArduinoRS485 library |
| 15 | +#include <ArduinoModbus.h> |
| 16 | + |
| 17 | +constexpr auto baudrate { 19200 }; |
| 18 | + |
| 19 | +// Calculate preDelay and postDelay in microseconds as per Modbus RTU Specification |
| 20 | +// |
| 21 | +// MODBUS over serial line specification and implementation guide V1.02 |
| 22 | +// Paragraph 2.5.1.1 MODBUS Message RTU Framing |
| 23 | +// https://modbus.org/docs/Modbus_over_serial_line_V1_02.pdf |
| 24 | +constexpr auto bitduration { 1.f / baudrate }; |
| 25 | +constexpr auto wordlen { 9.6f }; // try also with 10.0f |
| 26 | +constexpr auto preDelayBR { bitduration * wordlen * 3.5f * 1e6 }; |
| 27 | +constexpr auto postDelayBR { bitduration * wordlen * 3.5f * 1e6 }; |
| 28 | + |
| 29 | +void setup() { |
| 30 | + Serial.begin(9600); |
| 31 | + while (!Serial); |
| 32 | + |
| 33 | + Serial.println("Modbus RTU Client Toggle w/ Parameters"); |
| 34 | + |
| 35 | + RS485.setDelays(preDelayBR, postDelayBR); |
| 36 | + |
| 37 | + // start the Modbus RTU client in 8E1 mode |
| 38 | + if (!ModbusRTUClient.begin(baudrate, SERIAL_8E1)) { |
| 39 | + Serial.println("Failed to start Modbus RTU Client!"); |
| 40 | + while (1); |
| 41 | + } |
| 42 | +} |
| 43 | + |
| 44 | +void loop() { |
| 45 | + // for (slave) id 1: write the value of 0x01, to the coil at address 0x00 |
| 46 | + if (!ModbusRTUClient.coilWrite(1, 0x00, 0x01)) { |
| 47 | + Serial.print("Failed to write coil! "); |
| 48 | + Serial.println(ModbusRTUClient.lastError()); |
| 49 | + } |
| 50 | + |
| 51 | + // wait for 0.5 second |
| 52 | + delay(500); |
| 53 | + |
| 54 | + // for (slave) id 1: write the value of 0x00, to the coil at address 0x00 |
| 55 | + if (!ModbusRTUClient.coilWrite(1, 0x00, 0x00)) { |
| 56 | + Serial.print("Failed to write coil! "); |
| 57 | + Serial.println(ModbusRTUClient.lastError()); |
| 58 | + } |
| 59 | + |
| 60 | + // wait for 0.5 second |
| 61 | + delay(500); |
| 62 | + |
| 63 | + auto coil = ModbusRTUClient.coilRead(0x02, 0x00); |
| 64 | + |
| 65 | + if (coil < 0) { |
| 66 | + Serial.print("Failed to read coil: "); |
| 67 | + Serial.println(ModbusRTUClient.lastError()); |
| 68 | + } else { |
| 69 | + Serial.print("Coil: "); |
| 70 | + Serial.println(coil); |
| 71 | + } |
| 72 | + |
| 73 | + // wait for 0.5 second |
| 74 | + delay(500); |
| 75 | +} |
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