Three bytes sending

Connectivity RealDash CAN
1

Kilometers are in three bytes.
With this i can get correct value of kilometers from can-bus:

if (canId == 0x540) {
      uint32_t odometer = (uint32_t)rxBuf[7] <<16;
      odometer |=  rxBuf[6]<<8;
      odometer |=  rxBuf[5];

I cannot get it how to send three bytes with realdashcan, this does not work:

  buf[0] = (0xff);
  buf[1] = (0xff);
  buf[2] = (0xff);
  buf[3] = (0xff);
  buf[4] = (0xff);
  buf[5] = ((odometer  & 0xff);
  buf[6] = ((odometer >> 8) & 0xff);
  buf[7] = ((odometer >> 16) & 0xff);

In what form and order it should be written?

2

Looks ok to me, just use offset=“5” length=“3” in XML. Could you give more details of what is wrong?

3

In XML i have all like that. Target id is 310 (odometer).
After making this sketch, text gauge shows 1000000 when i turn ignition on, so something goes wrong.

4

I want to make a test and somehow put buf5-7 together and print value to a serial monitor.
Something like this?
It print value “156”

Serial.println(buf[5] + buf[6] + buf[7])

or

Serial.println(buf[5]  & 0ff) + (buf[6] << 8) +  (buf[7] << 16);

Also i tried to turn around all like buf7+buf6+buf5 and in can-frame sending code i tried to change all with same princible, what ever i do it print 0, 127 or 156, right value should be about 489000.

5

I can do some tests, but if you believe the problem is the 3 byte value, you can try to send the data in 4 bytes instead, just set most significant byte to 0.

6

I got some help in Arduino forum and for now i solved it like this:

else if (rxId == 0x520) {
      uint32_t rawOdo = (uint32_t)rxBuf[7] << 16;
      rawOdo |= (uint32_t) rxBuf[6] <<8;
      rawOdo |= rxBuf[5];
      odometer = rawOdo;

buf[0] = (0xff);
  buf[1] = (0xff);
  buf[2] = (0xff);
  buf[3] = (0xff);
  buf[4] = (0xff);
  buf[5] = ((odometer  & 0xff);
  buf[6] = ((odometer >> 8) & 0xff);
  buf[7] = ((odometer >> 16) & 0xff);
1 Like
7

New problem with fuel consumption and trip meter values.
I have fuel consumption as a double variable, trip meter is uint16_t.
Tried to send it in one byte (buf[]), it showed ok in RealDash, but without decimal points.
After updating RealDash to newest version, trip meter kilometers began to go back and forth, for example if there were about 2 kilometers, it blinks from 1 to 2 or 2 to 3.
Then i tried in same way as above in last post, but of course it says “invalid operands of types ‘double’ and ‘int’ to binary 'operator& '”
It is correct to send trip meter value in two bytes and fuel consumption in 4 bytes and how i get decimal points to fuel consumption value?

8

Blinking was because it tried to take kilometers from two different variables.

9

Trip1 kilometers does not fluctuate but fuel consumption and average speed does.

// build 8th CAN frame, trip1 & avg speed
  buf[0] = (trip1 & 0xff);
  buf[1] = (trip1 >> 8 & 0xff);
  buf[2] = averageTrip1Speed;
  buf[3] = (0xff);
  buf[4] = (0xff);
  buf[5] = (0xff);
  buf[6] = (0xff);
  buf[7] = (0xff);

  // write 8th CAN frame to serial
  SendCANFrameToSerial(07, buf);


// build 9th CAN frame, fuel consumption
  memcpy(buf, &trip1FuelConsumption, 4);
  
  // write 9th CAN frame to serial
  SendCANFrameToSerial(08, buf);

<frame id="3207">
		<value targetId="311" offset="0" length="2"></value> <!--Trip1-->
		<value name="Trip1 average speed" offset="2" length="1"></value> 
	</frame>
  
	<frame id="3208">
		<value name="Trip1 fuel consumption" offset="0" length="4" float="true"></value> 
		<value name="Trip2 fuel consumption" offset="4" length="4" float="true"></value> 
	</frame>