filth
August 23, 2015, 12:58pm
1
Hi,
im trying to read some data from an automotive ECU which is sending 5 data packets. Can IDs are 0x2000, 0x2001, 0x2002, 0x2003, 0x2004 and 0x2005.
Overall communication is working, i receive data - actually i only need ids 2000, 2001 and 2003. My issue is, that obviously im not reading messages quick enough, so they get lost.
My Code:
#include <mcp_can.h>#include <SPI.h>
long unsigned int rxId;
MCP_CAN CAN0(10); // Set CS to pin 10
void setup()
Serial.begin(115200);
int canStatus = CAN0.begin(CAN_1000KBPS);
attachInterrupt(0, blink, CHANGE);
void blink() {
while(digitalRead(2) == LOW) {
}
void loop()
Output:
Can init ok!
As you see, id 2003 is missing completely. Anyone got a clue, what im doing wrong, or how to improve this?
Thanks
system
August 23, 2015, 1:11pm
2
You can't do Serial output in an interrupt service routine.
ISRs are supposed to be lightening fast. Yours is not even close to being jiffy.
filth
August 23, 2015, 2:32pm
3
Thanks for the suggestion.
I already tried this option:
#include <mcp_can.h>
#include <SPI.h>
long unsigned int rxId;
unsigned char len = 0;
unsigned char rxBuf[8];
boolean interruptFlag = false;
MCP_CAN CAN0(10); // Set CS to pin 10
void setup()
{
delay(1000);
Serial.begin(115200);
int canStatus = CAN0.begin(CAN_1000KBPS);
if (canStatus != 0) {
Serial.println("Can init failed!");
}
else {
Serial.println("Can init ok!");
}
attachInterrupt(0, blink, CHANGE);
}
void blink() {
interruptFlag = true;
}
void loop()
{
if(interruptFlag) {
while(CAN_MSGAVAIL == CAN0.checkReceive())
{
CAN0.readMsgBuf(&len, rxBuf);
rxId = CAN0.getCanId(); // Get message ID
Serial.print("id: ");
Serial.println(rxId, HEX);
}
interruptFlag = false;
}
}
It doesnt work at all. Output of above code:
Can init ok!
I know that its possible to use masks and filters with the can shield, but i didnt figured out, how to use them properly. I think that would be the key to my problem. Anyone familiar with the Filters? Or other suggestions?
Thanks a lot!
filth
August 23, 2015, 2:57pm
4
Sorry my fault, cable wasnt plug in correctly...
So with this code
#include <mcp_can.h>
#include <SPI.h>
long unsigned int rxId;
unsigned char len = 0;
unsigned char rxBuf[8];
boolean interruptFlag = false;
MCP_CAN CAN0(10); // Set CS to pin 10
void setup()
{
delay(1000);
Serial.begin(115200);
int canStatus = CAN0.begin(CAN_1000KBPS);
if (canStatus != 0) {
Serial.println("Can init failed!");
}
else {
Serial.println("Can init ok!");
}
attachInterrupt(0, blink, CHANGE);
}
void blink() {
interruptFlag = true;
}
void loop()
{
if(interruptFlag) {
while(CAN_MSGAVAIL == CAN0.checkReceive())
{
CAN0.readMsgBuf(&len, rxBuf);
rxId = CAN0.getCanId(); // Get message ID
Serial.print("id: ");
Serial.println(rxId, HEX);
}
interruptFlag = false;
}
}
Im getting this output. So there are still messages missing
Can init ok!
system
August 23, 2015, 3:57pm
5
Variables shared by interrupt service routines and other functions must be volatile.
There is nothing magic, or smart, about the interrupt service routine's name.
PaulS:
Even if they are a single byte?
system
August 23, 2015, 4:09pm
7
Even if they are a single byte?
The volatile keyword tells the compiler that it must fetch the value every time it is referenced. Size has nothing to do with that need.
Robin2
August 23, 2015, 4:09pm
8
What happens if you change
while(CAN_MSGAVAIL == CAN0.checkReceive())
to
if (CAN_MSGAVAIL == CAN0.checkReceive())
...R
filth
August 23, 2015, 4:28pm
9
Robin2:
while(CAN_MSGAVAIL == CAN0.checkReceive())
to
if (CAN_MSGAVAIL == CAN0.checkReceive())
...R
Then the ISR is only entered 2 times. As i remember, the pin stays low as long as there is data in the buffer.
I found this example, could anyone help me adjusting the filters to receive only 0x2003 id? Thanks!
http://www.hobbytronics.co.uk/download/leonardo-canbus/test_receive_filter.ino
Robin2
August 23, 2015, 4:54pm
10
filth:
That does not make sense to me.
You are using the ISR to identify if something has been received. How many items are received for every interrupt?
My concern is that the WHILE will delay the moment when interruptFlag is set back to false so that the next item can be detected.
And do you need a CHANGE interrupt or would RISING or FALLING be better ?
...R
filth
August 23, 2015, 5:01pm
11
The ECU is sending 5 Messages for every interrupt. Changing interrupt type does not help.
What about the filters?
Robin2
August 23, 2015, 6:33pm
12
filth:
Can you read the whole thing as a single item and split it up later - that should be faster. Serial.print() is slow.
Or perhaps you could read (say) 50 items into an array before you print any of them ?
Or maybe just read the 5 into an array before printing anything ?
Can you post a link to the datasheet for the mcp_can library that you are using ?
...R
filth
August 23, 2015, 7:19pm
13
Im using this Lib
I cant split stuff, as the messages are getting lost on the hardware side - im not able to read them fast enough from the can shield.
Robin2
August 24, 2015, 8:50am
14
filth:
I meant that you read them before you split them so that you can read them faster.
It is also a good idea to do experiments to see what works. Even if it cannot be a long term solution it may help to figure out the cause of the problem. Have you tried reading 50 values like I suggested ?
I will look at your link later today.
...R
Robin2
August 24, 2015, 10:47am
15
Have you tried the example with interrupts that is in the Library link
There are at least two notable differences
It uses a FALLING interrupt
It sets Flag_Recv = 0; as the first thing, not the last thing
and it seems to be using a lower speed.
...R