Help with custom communication

Using Arduino Networking, Protocols, and Devices
1

Hi I have this code
I ask 32 slaves for data
slave has 10 ms for response delay(10);
can I do this without delay?

const byte START_BYTE = 254;
const byte ASK_CONNECT_BYTE = 252;
const byte ASK_DATA_BYTE = 250;

byte mb[5];
byte received[4];

void setup() {
  Serial.begin(115200);
  Serial2.begin(9600);
}

void loop() {
  for (int i = 1; i <= 32; i++) { 
    askData(i);
  }
}

void askData(int device) {
  sendMessage(device, ASK_DATA_BYTE, 0);
  delay(10);
  readMessage(received);

  if (validateReceived(received)) {
    if (received[0] == device) {
      Serial.println("----------");
      Serial.print("device: ");
      Serial.println(device);
      Serial.print("key: ");
      Serial.println(received[1]);
      Serial.print("value: ");
      Serial.println(received[2]);
      Serial.println("----------");
    }
  }
}

bool validateReceived(byte *received) {
  if (received[0] == 0 && received[3] == 0) {
    return false;
  }

  byte receivedChecksum = received[3];
  byte calculatedChecksum = START_BYTE + received[0] + received[1] + received[2];
  calculatedChecksum = ~calculatedChecksum;

  if (receivedChecksum == calculatedChecksum) {
    return true;
  }

  return false;
}

void readMessage(byte *received) {
  memset(received, 0, 4);

  if (Serial2.available()) {
    byte b = Serial2.read();

    if (b == START_BYTE) {
      Serial2.readBytes(received, 4);
    }
  }
}

void sendMessage(int device, byte key, byte value) {
  memset(mb, 0, 5);
  mb[0] = START_BYTE;
  mb[1] = device;
  mb[2] = key;
  mb[3] = value;
  byte checksum = mb[0] + mb[1] + mb[2] + mb[3];
  mb[4] = ~checksum;

  Serial2.write((uint8_t *)&mb, sizeof(mb));
  Serial2.flush();
}
2

I need in real time data from value, for example if is button pushed.

3

Yes it can be done without using delay(x).

Look at File|Examples|02.Digital|BlinkWithoutDelay to use millis() for timing instead of delay().

https://majenko.co.uk/blog/our-blog-1/the-finite-state-machine-26

4

Your delay is 10 milliseconds. Is your button press repetition rate really in the range of 100 actuations per second?

i.e. will the user ever be allowed to register a less than 10ms press as a valid press?

You are waiting longer than that only because you structured your program to poll the clients "back to back" without servicing any other code.

5

The call of the delay() function is needed to synchronize the dataflow between the master and 32 slaves.

6

don't use the hardcoded delay.
send the askData
start receiving and processing as soon as something is in your RX Buffer (Serial.available)

Furthermore you could store a "requestStarted=millis()" and compare in loop if the slave runs in a timeout.
If so, ask the next slave.

2 Likes
7

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