keizen
August 13, 2023, 12:01am
1
Hi
The value I want in the final integer value (32000). There is actually an offset of 32000 on this value.
Question - in Arduino IDE how do I return this value from the frame ? I can return the 8 byte values but want this one for the display.
Apologies if this has been asked before - I did a search and there is a lot on CAN BUS but couldnt see this one.
Thanks
kolaha
August 13, 2023, 12:39am
2
sketch?
1 Like
Welcome! What do you mean by "CAN Bus intel format data"? Are you talking about the endian and little-endian? This link may be your answer: What are big-endian and little-endian? Definition from SearchNetworking
keizen
August 13, 2023, 2:43am
4
Here is the code - it is the standard code in the examples folder
// CAN Receive Example
//
#include <mcp_can.h>
#include <SPI.h>
long unsigned int rxId;
unsigned char len = 0;
unsigned char rxBuf[8];
char msgString[128]; // Array to store serial string
#define CAN0_INT 2 // Set INT to pin 2
MCP_CAN CAN0(10); // Set CS to pin 10
void setup()
{
Serial.begin(115200);
// Initialize MCP2515 running at 16MHz with a baudrate of 500kb/s and the masks and filters disabled.
if(CAN0.begin(MCP_ANY, CAN_250KBPS, MCP_16MHZ) == CAN_OK)
Serial.println("MCP2515 Initialized Successfully!");
else
Serial.println("Error Initializing MCP2515...");
CAN0.setMode(MCP_NORMAL); // Set operation mode to normal so the MCP2515 sends acks to received data.
pinMode(CAN0_INT, INPUT); // Configuring pin for /INT input
Serial.println("MCP2515 Library Receive Example...");
}
void loop()
{
if(!digitalRead(CAN0_INT)) // If CAN0_INT pin is low, read receive buffer
{
CAN0.readMsgBuf(&rxId, &len, rxBuf); // Read data: len = data length, buf = data byte(s)
if((rxId & 0x80000000) == 0x80000000) // Determine if ID is standard (11 bits) or extended (29 bits)
sprintf(msgString, "Extended ID: 0x%.8lX Length: %1d Data:", (rxId & 0x1FFFFFFF), len);
else
sprintf(msgString, "Standard ID: 0x%.3lX DLC: %1d Data:", rxId, len);
Serial.print(msgString);
if((rxId & 0x40000000) == 0x40000000){ // Determine if message is a remote request frame.
sprintf(msgString, " REMOTE REQUEST FRAME");
Serial.print(msgString);
} else {
for(byte i = 0; i<len; i++){
sprintf(msgString, " 0x%.2X", rxBuf[i]);
Serial.print(msgString);
}
}
Serial.println();
}
}
/*********************************************************************************************************
END FILE
*********************************************************************************************************/
According to the document Byte 6 and 7 are the RPM with an offset of 32000
So when the motor isnt running this value should be 32,000 which is what shows in Can Hacker when I switch it to Intel format
The values provided by the code look like.
12:36:07.670 -> Extended ID: 0x180117EF Length: 8 Data: 0x1F 0x02 0x00 0x7D 0x00 0x7D 0x00 0x7D
I just want the RPM value so I can add it to the screen with the GPS speed.
Thanks !
mikb55
August 13, 2023, 4:59am
5
A single data point makes it difficult to see what is going on.
keizen
August 14, 2023, 3:15am
7
Perhaps but it still returns the correct data when displayed in CanHacker.
Thanks
mikb55
August 14, 2023, 6:17am
8
See figure 4, https://www.xanalyser.uk/wp-content/uploads/2020/11/Chapter-2-CAN-Signals-new.pdf
I cannot make sense of the CANHacker 'Integer Value' section of the display. There may be a field missing on the left, then it would make sense as 4 pairs of 16 bit value high/low , low/high values.
Using the data from the Arduino, if you look at the last 2 bytes, multiply the high byte 0x7D by 2^8 then add the low byte 0x0 you get 32000 decimal.
kolaha
August 14, 2023, 8:19am
9
// CAN Receive Example
//
#include <mcp_can.h>
#include <SPI.h>
long unsigned int rxId;
unsigned char len = 0;
unsigned char rxBuf[8];
char msgString[128]; // Array to store serial string
#define CAN0_INT 2 // Set INT to pin 2
MCP_CAN CAN0(10); // Set CS to pin 10
void setup() {
Serial.begin(115200);
if (CAN0.begin(MCP_ANY, CAN_250KBPS, MCP_16MHZ) == CAN_OK)Serial.println("MCP2515 Initialized Successfully!");
else Serial.println("Error Initializing MCP2515...");
CAN0.setMode(MCP_NORMAL); // Set operation mode to normal so the MCP2515 sends acks to received data.
pinMode(CAN0_INT, INPUT); // Configuring pin for /INT input
Serial.println("MCP2515 Library Receive Example...");
}
void loop() {
if (!digitalRead(CAN0_INT)) { // If CAN0_INT pin is low, read receive buffer
CAN0.readMsgBuf(&rxId, &len, rxBuf); // Read data: len = data length, buf = data byte(s)
if ((rxId & 0x80000000) == 0x80000000)sprintf(msgString, "Extended ID: 0x%.8lX Length: %1d Data:", (rxId & 0x1FFFFFFF), len);
else sprintf(msgString, "Standard ID: 0x%.3lX DLC: %1d Data:", rxId, len); // Determine if ID is standard (11 bits) or extended (29 bits)
Serial.print(msgString);
if ((rxId & 0x40000000) == 0x40000000) { // Determine if message is a remote request frame.
sprintf(msgString, " REMOTE REQUEST FRAME");
Serial.print(msgString);
} else {
for (byte i = 0; i < len; i++) {
sprintf(msgString, " 0x%.2X", rxBuf[i]);
Serial.print(msgString);
}
Serial.println();
}
Serial.println(rxBuf[len - 1] * 256 + rxBuf[len - 2]);
}
}
keizen
August 15, 2023, 2:20am
10
Works perfectly - thanks mate.
Can I ask for my own learning - why did you 'len - 1' and 'len - 2' instead of the byte number rxBuf[7] ?
Thanks again !
kolaha
August 15, 2023, 10:45am
11
today i think that 'len - 1' is not so good idea.
system
February 11, 2024, 10:46am
12
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.
