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I am trying to do a CAN data transfer from one LaunchXL-F28379D card to another to prototype an application for a client, using the C2000ware API. I have been unsuccessful at properly decoding the received data. So I found two example projects in C2000ware, can_ex4_simple_transmit and can_ex5_simple_receive, which I could modify for use on the LaunchXL-F28379D, to verify that the LaunchXL boards will support that operation.
The changes I have made in my versions of the projects are:
1) Used CAN-B instead of CAN-A, because by default, the CAN port pins on the LaunchXL boards use GPIO pins assigned to CAN-B;
2) Changed the LED toggled to use GPIO31 to drive LED1 on the LaunchXL boards. I also toggle GPIO15, a pin readily available in the LaunchXL booster pin banks, so I can send an output signal to an oscilloscope.
3) Inserted a delay at the end of each transmit to be able to visually separate the packets sent on an oscilloscope. The delay could be shortened or extended to make the LED blinks humanly perceptible.
4) Used the optional for loop instead of while in the Tx project so I could easily halt Tx at a known Tx count, and then verify that # of packets received matches # of packets sent, and that data content received matches data content sent.
5) Added predefined symbols CPU1 for single CPU operation and _LAUNCHXL_F28379D to select C2000ware resources for that board.
When I run the two modified example programs in the CCS debugger (CCS v10.4, compiler v20.4, C2000ware 3.4.0), the packet count does match. But the Rx data always appears as only 0x00 data bytes. This appears to be similar to the problem I have encountered with my project in development. My expectation was that, if both CAN example programs work correctly, data received by the simple Rx program would match data sent by the Tx program.
I would like to attach a ZIP file containing both projects, so you can review them to see if I have introduced any errors. I don't see a way to send a ZIP file. Can you tell me how I can get a copy of those projects to you?
Failing that, can you create a pair of Rx and Tx projects with similar changes to those I made for use on LaunchXL-F28379D, that does successfully receive the transmitted data, so I can see how you do it?
It is possible that the simple Tx and simple Rx example projects were not designed as a compatible pair. If so, what modifications can I make so that the simple Rx program will properly decode data sent by the simple Tx program?
In answer to your questions, not in the order asked:
2) The hardware for CANB on LaunchXL-F28379D has CANH and CANL pins, not CANTX and CANRX. The latter are fed through an onboard transducer, and there is no easy way to access those signals
1) My client is planning to build a cable that adds a DB9 T-tap between CANH and CANL, which we can then attach to a Peak CAN adapter to listen and log data sent between the two LaunchXL boards. I have not had the opportunity to get that data yet. When we do, it will help determine whether the problem is on the Tx or Rx side.
3) Yes, apparently frames are received, since number received equals number sent. We monitor that by adding to the Expressions tab of CCS debugger the variable i in the Tx loop of the Tx program, and variable rxMsgCount in the Rx program. Packet contents can be monitored when programs are paused by adding to Expressions variable rxMsgData or rxLastDataRcvd in the Rx program and the variable txMsgData on the Tx program.
I made the change to the ARBID parameter as you suggested. Behavior of the system has not changed. All data bytes in the Rx program are decoded as 0x00.
2) The hardware for CANB on LaunchXL-F28379D has CANH and CANL pins, not CANTX and CANRX. The latter are fed through an onboard transducer, and there is no easy way to access those signals
Yes, I am aware. You could probe the pins on the transceiver itself, but understand it is a little hard.
I just noticed that, as the projects came from C2000ware, Tx uses CAN_MSG_FRAME_EXT and Rx uses CAN_MSG_FRAME_STD. I changed both to use STD. That solved the problem.
I had highlighted this in my previous message. perhaps you missed it?
