ANT BMS sometimes won't communicate via UART

Hello everyone. Currently my ANT BMS sometimes works, and sometimes won't communicate with my arduino nano. I thought there's hardware issues so i did hardware debugging (checking for loose wire, etc) for a while. Then my ant bms started to sending data again to my arduino normally.

But after i turn off my arduino and turning on again, the ANT BMS won't sending data to my arduino nano. I don't know why because in the previous experiment was succesful. Any idea why? This my code. Thank you.

#include <stdint.h>
#include <SoftwareSerial.h>

#define RX 8       // Arduino defined pin (PB0, package pin #5)
#define TX 9       // Arduino defined pin (PB1, package pin #6)

SoftwareSerial mySerial(RX, TX);

const unsigned char request_bms[] = {0x5A,0x5A,0x00,0x00,0x00,0x00};
unsigned long heartbeatMillis, timeoutMillis;
unsigned char serialBuffer[140];

unsigned int serialCursor = 0;

int current = 0;
uint16_t voltage = 0;
int16_t temperature = 0;
uint8_t percentage = 0;

void setup() {
  memset(serialBuffer, 0, sizeof(serialBuffer));
  
  Serial.begin(115200);
  mySerial.begin(19200);
  Serial.println("Ready!");
}

void loop() {
  const unsigned long currentMillis = millis();
  const unsigned long deltaTimeoutMillis = currentMillis - timeoutMillis;
  
  if (serialCursor > sizeof(serialBuffer))
    serialCursor = 0;
  
  if (deltaTimeoutMillis > 500) {
    for (unsigned int i = 0; i < sizeof(request_bms); i++)
      mySerial.write(request_bms[i]);
    mySerial.flush();
    Serial.println("Requesting...");
    
    timeoutMillis = currentMillis;
    serialCursor = 0;
  }
  
  unsigned int serialRemaining = mySerial.available();
  if ((serialRemaining + serialCursor) > sizeof(serialBuffer)) {
    serialRemaining = sizeof(serialBuffer) - serialCursor;
  }
  while (serialRemaining) {
    timeoutMillis = currentMillis;
    if (serialCursor >= 140) break;
    unsigned char eachByte = mySerial.read();
    serialRemaining--;
    if (serialCursor == 3) {
      bool isInvalid = (serialBuffer[0] != 0xAA)
                       || (serialBuffer[1] != 0x55)
                       || (serialBuffer[2] != 0xAA)
                       || (eachByte != 0xFF);
      if (isInvalid) {
        Serial.println("Wrong start byte, retrying...");
        serialCursor = 0;
        continue;
      }
    }
    //Serial.print("Cursor: ");
    //Serial.println(serialCursor);
    serialBuffer[serialCursor] = eachByte;
    serialCursor++;
  }

  if (serialCursor != 140)
    return;

  serialCursor = 0;

  {
    uint16_t calculatedChecksum = 0;
    for (unsigned int i = 4; i < 138; i++)
      calculatedChecksum += serialBuffer[i];
  
    uint16_t expectedChecksum = (serialBuffer[138] << 8) + serialBuffer[139];
    if (calculatedChecksum != expectedChecksum) {
      Serial.println("Data corrupted.");
      return;
    }
  }

  current = serialBuffer[70];
  current <<= 8;
  current |= serialBuffer[71];
  current <<= 8;
  current |= serialBuffer[72];
  current <<= 8;
  current |= serialBuffer[73];
  Serial.print("Current: ");
  Serial.println(current);
  
  percentage = serialBuffer[74];
  Serial.print("SoC: ");
  Serial.println(percentage);

  temperature = serialBuffer[91];
  temperature <<= 8;
  temperature |= serialBuffer[92];
  Serial.print("Temperature: ");
  Serial.println(temperature);

  voltage = serialBuffer[121];
  voltage <<= 8;
  voltage |= serialBuffer[122];
  voltage = ((float)voltage) * (20.F / 1000.F);
  Serial.print("Voltage: ");
  Serial.println(voltage);

}

2 posts - 1 participant

Read full topic