Part Number:EK-TM4C1294XL
Hi,
I tried to test CAN communication between 2 custom made TM4C129ENCPDT boards with transceivers. For this I modified simple RX and simple TX example programs and flashed them to 2 separate boards and connected them. However, when the interrupt handler is hit, I see the error 0x05 after the error statement 0x8000 in the status register which is corresponding to bus off.
To test the validity of the code, i tried internal loopback(by configuring the test mode and internal loopback registers before enabling can using CAN_enable API) and am able to see status of 0x01 (corresponding to the TX message object ID) i.e. the internal loopback is working correctly.
Further I tried probing the transceiver for the loopback code and am able to see data in CAN TX pin of the transciever, but no data is seen at CAN_HI and CAN _LO pins of transciever .
What am I doing wrong?
The following is the code which I am using for CAN_Transmit(witht he loopback statements commented out):
#include "config.h"
#ifdef CAN_TX_ENABLE
#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_can.h"
#include "inc/hw_ints.h"
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "driverlib/can.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"
//*****************************************************************************
//
//! \addtogroup can_examples_list
//! <h1>Simple CAN TX (simple_tx)</h1>
//!
//! This example shows the basic setup of CAN in order to transmit messages
//! on the CAN bus. The CAN peripheral is configured to transmit messages
//! with a specific CAN ID. A message is then transmitted once per second,
//! using a simple delay loop for timing. The message that is sent is a 4
//! byte message that contains an incrementing pattern. A CAN interrupt
//! handler is used to confirm message transmission and count the number of
//! messages that have been sent.
//!
//! This example uses the following peripherals and I/O signals. You must
//! review these and change as needed for your own board:
//! - CAN0 peripheral
//! - GPIO Port A peripheral (for CAN0 pins)
//! - CAN0RX - PA0
//! - CAN0TX - PA1
//!
//!
//! This example uses the following interrupt handlers. To use this example
//! in your own application you must add these interrupt handlers to your
//! vector table.
//! - INT_CAN0 - CANIntHandler
//
//*****************************************************************************
//*****************************************************************************
//
// A counter that keeps track of the number of times the TX interrupt has
// occurred, which should match the number of TX messages that were sent.
//
//*****************************************************************************
volatile uint32_t g_ui32MsgCount = 0;
//*****************************************************************************
//
// A flag to indicate that some transmission error occurred.
//
//*****************************************************************************
volatile bool g_bErrFlag = 0;
//*****************************************************************************
//
// This function provides a 1 second delay using a simple polling method.
//
//*****************************************************************************
void
SimpleDelay(void)
{
//
// Delay cycles for 1 second
//
SysCtlDelay(16000000 / 3);
}
//*****************************************************************************
//
// This function is the interrupt handler for the CAN peripheral. It checks
// for the cause of the interrupt, and maintains a count of all messages that
// have been transmitted.
//
//*****************************************************************************
void
CANIntHandler(void)
{
uint32_t ui32Status;
//
// Read the CAN interrupt status to find the cause of the interrupt
//
ui32Status = CANIntStatus(CAN0_BASE, CAN_INT_STS_CAUSE);
//
// If the cause is a controller status interrupt, then get the status
//
if(ui32Status == CAN_INT_INTID_STATUS)
{
//
// Read the controller status. This will return a field of status
// error bits that can indicate various errors. Error processing
// is not done in this example for simplicity. Refer to the
// API documentation for details about the error status bits.
// The act of reading this status will clear the interrupt. If the
// CAN peripheral is not connected to a CAN bus with other CAN devices
// present, then errors will occur and will be indicated in the
// controller status.
//
ui32Status = CANStatusGet(CAN0_BASE, CAN_STS_CONTROL);
//
// Set a flag to indicate some errors may have occurred.
//
g_bErrFlag = 1;
}
//
// Check if the cause is message object 1, which what we are using for
// sending messages.
//
else if(ui32Status == 1)
{
//
// Getting to this point means that the TX interrupt occurred on
// message object 1, and the message TX is complete. Clear the
// message object interrupt.
//
CANIntClear(CAN0_BASE, 1);
//
// Increment a counter to keep track of how many messages have been
// sent. In a real application this could be used to set flags to
// indicate when a message is sent.
//
g_ui32MsgCount++;
//
// Since the message was sent, clear any error flags.
//
g_bErrFlag = 0;
}
//
// Otherwise, something unexpected caused the interrupt. This should
// never happen.
//
else
{
//
// Spurious interrupt handling can go here.
//
}
}
//*****************************************************************************
//
// Configure the CAN and enter a loop to transmit periodic CAN messages.
//
//*****************************************************************************
int
main(void)
{
#if defined(TARGET_IS_TM4C129_RA0) || \
defined(TARGET_IS_TM4C129_RA1) || \
defined(TARGET_IS_TM4C129_RA2)
uint32_t ui32SysClock;
#endif
tCANMsgObject sCANMessage;
tCANMsgObject sCANMessage1;
uint32_t ui32MsgData;
uint8_t *pui8MsgData;
pui8MsgData = (uint8_t *)&ui32MsgData;
//
// Set the clocking to run directly from the external crystal/oscillator.
// TODO: The SYSCTL_XTAL_ value must be changed to match the value of the
// crystal on your board.
//
#if defined(TARGET_IS_TM4C129_RA0) || \
defined(TARGET_IS_TM4C129_RA1) || \
defined(TARGET_IS_TM4C129_RA2)
ui32SysClock = SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
SYSCTL_OSC_MAIN |
SYSCTL_USE_OSC)
25000000);
#else
SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
SYSCTL_XTAL_16MHZ);
#endif
//
// Set up the serial console to use for displaying messages. This is
// just for this example program and is not needed for CAN operation.
//
// InitConsole();
//
// For this example CAN0 is used with RX and TX pins on port B4 and B5.
// The actual port and pins used may be different on your part, consult
// the data sheet for more information.
// GPIO port B needs to be enabled so these pins can be used.
// TODO: change this to whichever GPIO port you are using
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
//
// Configure the GPIO pin muxing to select CAN0 functions for these pins.
// This step selects which alternate function is available for these pins.
// This is necessary if your part supports GPIO pin function muxing.
// Consult the data sheet to see which functions are allocated per pin.
// TODO: change this to select the port/pin you are using
//
GPIOPinConfigure(GPIO_PA0_CAN0RX);
GPIOPinConfigure(GPIO_PA1_CAN0TX);
//
// Enable the alternate function on the GPIO pins. The above step selects
// which alternate function is available. This step actually enables the
// alternate function instead of GPIO for these pins.
// TODO: change this to match the port/pin you are using
//
GPIOPinTypeCAN(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);
//
// The GPIO port and pins have been set up for CAN. The CAN peripheral
// must be enabled.
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_CAN0);
//
// Initialize the CAN controller
//
CANInit(CAN0_BASE);
//
// Set up the bit rate for the CAN bus. This function sets up the CAN
// bus timing for a nominal configuration. You can achieve more control
// over the CAN bus timing by using the function CANBitTimingSet() instead
// of this one, if needed.
// In this example, the CAN bus is set to 500 kHz. In the function below,
// the call to SysCtlClockGet() or ui32SysClock is used to determine the
// clock rate that is used for clocking the CAN peripheral. This can be
// replaced with a fixed value if you know the value of the system clock,
// saving the extra function call. For some parts, the CAN peripheral is
// clocked by a fixed 8 MHz regardless of the system clock in which case
// the call to SysCtlClockGet() or ui32SysClock should be replaced with
// 8000000. Consult the data sheet for more information about CAN
// peripheral clocking.
//
#if defined(TARGET_IS_TM4C129_RA0) || \
defined(TARGET_IS_TM4C129_RA1) || \
defined(TARGET_IS_TM4C129_RA2)
CANBitRateSet(CAN0_BASE, ui32SysClock, 500000);
#else
CANBitRateSet(CAN0_BASE, SysCtlClockGet(), 500000);
#endif
//
// Enable interrupts on the CAN peripheral. This example uses static
// allocation of interrupt handlers which means the name of the handler
// is in the vector table of startup code. If you want to use dynamic
// allocation of the vector table, then you must also call CANIntRegister()
// here.
//
// CANIntRegister(CAN0_BASE, &CANIntHandler); // if using dynamic vectors
//
HWREG(CAN0_BASE+CAN_O_CTL) |= CAN_CTL_TEST;
HWREG(CAN0_BASE+CAN_O_TST) |= CAN_TST_LBACK;
CANIntEnable(CAN0_BASE, CAN_INT_MASTER | CAN_INT_ERROR | CAN_INT_STATUS);
//
// Enable the CAN interrupt on the processor (NVIC).
//
IntEnable(INT_CAN0);
//
// Enable the CAN for operation.
//
CANEnable(CAN0_BASE);
//
// Initialize the message object that will be used for sending CAN
// messages. The message will be 4 bytes that will contain an incrementing
// value. Initially it will be set to 0.
//
ui32MsgData = 0;
sCANMessage.ui32MsgID = 1;
sCANMessage.ui32MsgIDMask = 0;
sCANMessage.ui32Flags = MSG_OBJ_TX_INT_ENABLE;
sCANMessage.ui32MsgLen = sizeof(pui8MsgData);
sCANMessage.pui8MsgData = pui8MsgData;
//
// Initialize a message object to be used for receiving CAN messages with
// any CAN ID. In order to receive any CAN ID, the ID and mask must both
// be set to 0, and the ID filter enabled.
//
// sCANMessage1.ui32MsgID = 0;
// sCANMessage1.ui32MsgIDMask = 0;
// sCANMessage1.ui32Flags = MSG_OBJ_RX_INT_ENABLE | MSG_OBJ_USE_ID_FILTER;
// sCANMessage1.ui32MsgLen = 8;
//
// Enter loop to send messages. A new message will be sent once per
// second. The 4 bytes of message content will be treated as an uint32_t
// and incremented by one each time.
//
while(1)
{
//
// Send the CAN message using object number 1 (not the same thing as
// CAN ID, which is also 1 in this example). This function will cause
// the message to be transmitted right away.
//
CANMessageSet(CAN0_BASE, 1, &sCANMessage, MSG_OBJ_TYPE_TX);
//
// Now load the message object into the CAN peripheral. Once loaded the
// CAN will receive any message on the bus, and an interrupt will occur.
// Use message object 1 for receiving messages (this is not the same as
// the CAN ID which can be any value in this example).
//
// CANMessageSet(CAN0_BASE, 2, &sCANMessage1, MSG_OBJ_TYPE_RX);
//
// Now wait 1 second before continuing
//
SimpleDelay();
//
// Increment the value in the message data.
//
ui32MsgData++;
}
//
// Return no errors
//
return(0);
}
#endif
