Return CAN

fernandokestering · Joined: 03 Sep 2018 Posts: 21

I was able to make the CAN network return something, it follows:
CAN_GETD (): BUFF = 1 ID = 0CFE6CEE LEN = 8 OVF = 1 FILT = 2 RTR = 0 EXT = 1 INV = 0
DATA = 00 3F FF C0 00 00 00 00

However, it is not yet valid data to be recognized by the J1939 library provided by CCS.
The bus speed is 250kbps.

temtronic · Posted: Thu Sep 06, 2018 6:10 am

quick comment

While I don't use CAN, first place to look is PIC clock speed. You'll need to use a real xtal/2caps configuration, then check actual clock frequency as well as CAN clock speed. Both of these must be confirmed as if either is 'off' just a tad... the CAN data could be slewed or corrupted.
Others, who use the CCS CAN driver can help with the setup/configuration, though you'll have to provide them more details.

Jay

fernandokestering · Joined: 03 Sep 2018 Posts: 21

I am using the PIC18f4520 with a frequency of 20Mhz and the MCP2515 also with a frequency of 20Mhz.
Configuration of the MCP2515:

J1939_BAUD_RATE == 250000

#define CAN_BRG_PRESCALAR 3
#define CAN_BRG_PHASE_SEGMENT_1 3
#define CAN_BRG_PHASE_SEGMENT_2 3
#define CAN_BRG_PROPAGATION_TIME 0
#define CAN_BRG_SYNCH_JUMP_WIDTH 0

fernandokestering · Joined: 03 Sep 2018 Posts: 21

The program gets stuck in a loop in the 1939ReceiveTask (); // J1939ReceiveTask (). Has anyone ever had this problem?

temtronic · Posted: Thu Sep 06, 2018 12:35 pm

Does your CAN I/F have the proper pullups/terminators ?
IS the PIC SW configured for the other CAN device (same speed, etc )?

fernandokestering · Joined: 03 Sep 2018 Posts: 21

I am receiving this information from the CAN network, PGN 65217 (total distance)
18FEC1EE
DATA = C2 45 73 00 3E 3D 73 00
How do I convert to KM?

temtronic · Posted: Thu Sep 06, 2018 2:45 pm

I'd say read the manual or datasheet for the device transmitting that data to the PIC. It HAS to be documented.
I could 'guess' and say each byte is one digit of the odometer reading in some weird, abstract encoding though I'd use PBCD.

newguy · Joined: 24 Jun 2004 Posts: 1900

Did you try googling "pgn 65217"?

http://www.copperhilltechnologies.com/electronic-logging-devices-eld-sae-j1939-and-sae-j1708j1587-parameters/

0x7345c2 = 7554498. The units are "5m / count", so multiply by 5 to get 37,772,490. Convert to km by dividing by 1000: 37,772.490 km.

fernandokestering · Joined: 03 Sep 2018 Posts: 21

Hi newguy
Thanks!!!![/code]

temtronic · Posted: Fri Sep 07, 2018 5:08 am

The reference newguy posted doesn't say the data elements are reversed..hmmm
DATA = C2 45 73 00 3E 3D 73 00

while the data is split, 4 bytes = total distance, 4 bytes are 'trip' distance

'somewhere' newguy saw that
C2 45 73 00 has to be reversed into 00 73 45 C2
something I would not have known to do.
It also requires more code to complete the task.

It does point out that you NEED to find original documentation about ! In this case , locate the SAE J1939 papers.

Jay

newguy · Joined: 24 Jun 2004 Posts: 1900