Problem Sending CAN Message

andy2399 · ‎2018-04-15

Posted on April 15, 2018 at 23:27

I am following the example code found here to send and receive CAN messages:

STM32Cube_FW_F4_V1.21.0\Projects\STM324xG_EVAL\Examples\CAN\CAN_Networking\Src

I can happily receive CAN messages but when I call the following code, the CAN message is never sent.

HAL_CAN_AddTxMessage( &hcan1, &TxHeader, TxData, &TxMailbox );

while(HAL_CAN_GetTxMailboxesFreeLevel(&hcan1) != 3) {}

TxHeader is configured as:

TxHeader.StdId = 0x123;

TxHeader.ExtId = 0x01;

TxHeader.RTR = CAN_RTR_DATA;

TxHeader.IDE = CAN_ID_STD;

TxHeader.DLC = 7;

TxHeader.TransmitGlobalTime = DISABLE;

And TxData is filled with seven bytes of data.

HAL_CAN_GetTxMailboxesFreeLevel always returns 2 and I don't see the CAN message on the bus.

Any help or idea would be gratefully appreciated.

Andy

T J · ‎2018-04-15

Posted on April 16, 2018 at 01:39

Hi,

are you using 2 devices ? on a CanBus ? with a line driver ?

You can receive but not transmit.

Are there only two devices on the bus ?

Did you turn on the ABOM enable ?

When you transmit, make sure no two devices never transmit the same msgID.

andy2399 · ‎2018-04-16

Posted on April 16, 2018 at 10:04

Thank you for your interest in my problem.

There are two devices on my bus both with line drivers and both ends terminated.

I am using a STM32F429 device with a SN65HVD230D CAN transceiver connected to a Microchip CAN Bus Analyser box which is configured to have bus termination enabled. I have the bit rate set to 20Kbps.

I assume ABOM is Auto Bus Off Management, in the latest HAL it is called AutoBusOff. I have that DISABLED however enabling it makes no difference.

Andy

andy2399 · ‎2018-04-16

Posted on April 16, 2018 at 10:41

Thanks for the code - you are using LL where I am trying to use the HAL but I gave it a go to see if it helped.

I modified your code to look like this:

if ( ( hcan1.Instance->TSR & CAN_TSR_TME0 ) == CAN_TSR_TME0 ) // (1)

{

hcan1.Instance->sTxMailBox[ 0 ].TDTR = 8;

hcan1.Instance->sTxMailBox[ 0 ].TDLR = 0x12345678;

hcan1.Instance->sTxMailBox[ 0 ].TDHR = 0xABCDEF12;

hcan1.Instance->sTxMailBox[ 0 ].TIR = ( ( uint32_t )0x123 << 21 | CAN_TI0R_TXRQ );

}

The first time in, the if statement executes but nothing appears to be launched onto the bus, thereafter, the if statement never becomes true.

Andy

andy2399 · ‎2018-04-16

Posted on April 16, 2018 at 10:55

I have interrupts enabled though I don't use them.

andy2399 · ‎2018-04-16

Posted on April 16, 2018 at 11:07

Okay, digging a little deeper (I was able to get a logic analyser on the bus). I do see a message being transmitted after all. However, it seems that it is not being ACK'd because the original message is continually being sent and all the transmit mailboxes are full. So I guess I have to dig a bit deeper into this :(

Andy

andy2399 · ‎2018-04-16

Posted on April 16, 2018 at 11:11

Even more strange, if I disable automatic re transmission it all works fine. The mailboxes never fill up and I see continually changing data in the messages.

Andy

T J · ‎2018-04-16

Posted on April 16, 2018 at 10:28

if you want the CanBs to recover from a hardware error, then best to enable ABOM.

I poll this code to transmit:

no interrupts are needed for Tx

if ((CAN->TSR & CAN_TSR_TME0) == CAN_TSR_TME0) // (1)

{

CAN->sTxMailBox[0].TDTR = canTxMsgLength[canTxMsgOUT]; // (2) length

CAN->sTxMailBox[0].TDLR = canTxMsgBottomWord[canTxMsgOUT]; // (3) 4bytes

CAN->sTxMailBox[0].TDHR = canTxMsgTopWord[canTxMsgOUT]; // (3) 4bytes

CAN->sTxMailBox[0].TIR = ((uint32_t)canTxMsgID[canTxMsgOUT] << 21 | CAN_TI0R_TXRQ); // (4) // send it now if the line is idle

// destroy old data to be sure we only transmit fresh data

// not needed

canTxMsgLength[canTxMsgOUT] = 0;

canTxMsgBottomWord[canTxMsgOUT] = 0;

canTxMsgTopWord[canTxMsgOUT] = 0;

canTxMsgID[canTxMsgOUT++] = 0;

canTxMsgOUT &= 0x3F; // 64 buffer elements

canTxMsgTableFULL = false;

canTxMsgOverrun = false;

//canMsgCounter ++;

}

if ((CAN->TSR & CAN_TSR_TME1) == CAN_TSR_TME1) // (1)

T J · ‎2018-04-16

Posted on April 16, 2018 at 10:47

I do enable interrupts, but dont use any Tx part of it,

like this : in startup, run only once never enable again

__HAL_CAN_ENABLE_IT(&hcan, CAN_IT_FMP1);

__HAL_CAN_ENABLE_IT(&hcan, CAN_IT_FMP0);

T J · ‎2018-04-16

Posted on April 16, 2018 at 11:10

I use the interrupts for the RX side.

only enable it once at startup