Unable to use readHoldingRegisters function sequentially

[its-me-vicky]

I am using esp8266 as master and in my slave device, the readings are at two separate addresses. I tried to use readHoldingRegisters function two times sequentially. At the first time it responses with (0, HEX) but on the second time it responses (4, HEX).

include

define RS485_EN D11

define RS485_RX D8

define RS485_TX D9

ModbusMaster node; SoftwareSerial RS485Serial(RS485_RX, RS485_TX); void preTransmission() { digitalWrite(RS485_EN, true); } void postTransmission() { digitalWrite(RS485_EN, false); } void setup() { Serial.begin(9600); RS485Serial.begin(9600); pinMode(RS485_EN, OUTPUT); digitalWrite(RS485_EN, false); } void loop() { delay(1000); uint16_t result[2], value[23]; node.preTransmission(preTransmission); node.postTransmission(postTransmission); node.begin(1, RS485Serial); result[0] = node.readHoldingRegisters(4096, 34); Serial.println(result[1], HEX); // this prints 0x00 if (result[0] == node.ku8MBSuccess) { for (uint8_t i = 0; i <= 34; i++) { Serial.println(node.getResponseBuffer(i)); } } node.clearResponseBuffer(); delay(1000); result[1] = node.readHoldingRegisters(16384, 25); Serial.println(result[1], HEX); // this prints 0x04 if (result[1] == node.ku8MBSuccess) { for (uint8_t i = 0; i <= 25; i++) { Serial.println(node.getResponseBuffer(i)); } } node.clearResponseBuffer(); }

If I create a new object and call the second API from it and it works perfectly!

[YagoDeleon]

On documentation "result" equal 0x04 represents : // static const uint8_t ku8MBSlaveDeviceFailure = 0x04 //Modbus protocol slave device failure exception.

[Haminacan]

I had to add a 10 millisecond delay between requests to get it to work for the device I was using.