Quick start guide for the SAM LIN module

This is the quick start guide for the LIN module, with step-by-step instructions on how to configure and use the driver in a selection of use cases.

The use cases contain several code fragments. The code fragments in the steps for setup can be copied into a custom initialization function, while the steps for usage can be copied into, e.g., the main application function.

LIN use cases

• LIN master use case - Setup LIN master.
• LIN slave use case - Setup LIN slave.

LIN master use case - Setup LIN master.

In this use case, the LIN node is set as a master PUBLISH. A specific data will be sent via it.

Prerequisites

1. General Purpose I/O Management (gpio)
2. Universal Synchronous Asynchronous Receiver Transmitter (USART)
3. Timer Counter (TC)

Code

The following definitions must be added to the project.

#define LIN_FRAME_ID_12    0x12
#define LIN_TRANSFER_BYTE    0x55
#define LIN_MASTER_NODE_NUM 0
#define TC_CHANNEL        0
#define TC_FREQ             20

An array for the transfer bytes must be added:

uint8_t lin_data_node[8];

The Timer Counter are used to generate period cycle for the LIN master transfer. More information about how to configure and use TC can be found at sam_drivers_tc_group.

void configure_tc(void)
{
   uint32_t ul_div;
   uint32_t ul_tcclks;
   static uint32_t ul_sysclk;

   ul_sysclk = sysclk_get_cpu_hz();

   pmc_enable_periph_clk(ID_TC0);

   tc_find_mck_divisor(TC_FREQ, ul_sysclk, &ul_div, &ul_tcclks, ul_sysclk);
   tc_init(TC0, 0, ul_tcclks | TC_CMR_CPCTRG);
   tc_write_rc(TC0, 0, (ul_sysclk / ul_div) / TC_FREQ);

   NVIC_EnableIRQ((IRQn_Type)ID_TC0);
   tc_enable_interrupt(TC0, 0, TC_IER_CPCS);
}

Add to application initialization:

{
   sysclk_init();
   board_init();

   pmc_enable_periph_clk(BOARD_ID_USART);

   lin_init( USART0, true, LIN_MASTER_NODE_NUM, 9600, sysclk_get_cpu_hz());

   lin_desc.uc_id = LIN_FRAME_ID_12;
   lin_desc.uc_dlc = sizeof(lin_data_node);
   lin_desc.lin_cmd = PUBLISH;
   lin_desc.uc_status = 0;
   lin_desc.uc_pt_data = lin_data_node;
   lin_register_desciptor(LIN_MASTER_NODE_NUM, 0, &lin_desc);

   configure_tc();
   tc_start(TC0, 0);
}

Workflow

1. LIN master node ID:

   #define LIN_FRAME_ID_12    0x12

2. First data of the transfer:

   #define LIN_TRANSFER_BYTE    0x55

3. Mater node number:

   #define LIN_MASTER_NODE_NUM 0

4. Timer Counter channel number:

   #define TC_CHANNEL        0

5. Timer Counter frequency:

   #define TC_FREQ             20

6. Initialize system clock:

   sysclk_init();

7. Initialize board peripherals:

   board_init();

8. Enable PMC for USART:

   pmc_enable_periph_clk(BOARD_ID_USART);

9. Initialize LIN master, set the master with baudrate 9600:

   lin_init( USART0, true, LIN_MASTER_NODE_NUM, 9600, sysclk_get_cpu_hz());

10. Set LIN master descriptor ID:

    lin_desc.uc_id = LIN_FRAME_ID_12;

11. Set LIN master descriptor transfer size:

    lin_desc.uc_dlc = sizeof(lin_data_node);

12. Set LIN master transfer type PUBLISHER:

    lin_desc.lin_cmd = PUBLISH;

13. Set LIN master default transfer status:

    lin_desc.uc_status = 0;

14. Set LIN master transfer data buffer:

    lin_desc.uc_pt_data = lin_data_node;

15. Setup the master descriptor:

    lin_register_desciptor(LIN_MASTER_NODE_NUM, 0, &lin_desc);

16. Initialize the Timer Counter:

    configure_tc();

17. Start the Timer Counter:

    configure_tc();

Use case

Example code

Add to application C-file:

void TC0_Handler(void)
{
   tc_get_status(TC0, 0);

   lin_data_node[0] = LIN_FIRST_BYTE;
   lin_send_cmd(LIN_MASTER_NODE_NUM, LIN_FRAME_ID_12,
           sizeof(lin_data_node));
}

Workflow

1. The LIN master period is generated by TC interrupt service routine:

   void TC0_Handler(void)

2. Clear Timer Counter status:

   tc_get_status(TC0, 0);

3. Set the first byte of the transfer:

   lin_data_node[0] = LIN_FIRST_BYTE;

4. Start the transfer:

   lin_send_cmd(LIN_MASTER_NODE_NUM, LIN_FRAME_ID_12,
        sizeof(lin_data_node));

LIN slave use case - Setup LIN slave.

In this use case, the LIN node is set as a slave subscriber. An LED will be flash when a specific data received.

Prerequisites

1. General Purpose I/O Management (gpio)
2. Universal Synchronous Asynchronous Receiver Transmitter (USART)
3. Timer Counter (TC)

Workflow

The following definitions must be added to the project.

#define LIN_FRAME_ID_12    0x12
#define LIN_SPECIFIC_BYTE    0x55
#define LIN_SLAVE_NODE_NUM 0

An array for the received byte must be added:

uint8_t lin_data_node[8];

The usart0 interrupt service handler must be created to receive the LIN frame.

void USART0_Handler(void)
{
     usart_lin_handler(LIN_SLAVE_NODE_NUM);
}

Add to application initialization:

{
   sysclk_init();
   board_init();

   pmc_enable_periph_clk(BOARD_ID_USART);

   lin_init( USART0, false, LIN_SLAVE_NODE_NUM, 9600, sysclk_get_cpu_hz());

   lin_desc.uc_id = LIN_FRAME_ID_12;
   lin_desc.uc_dlc = sizeof(lin_data_node);
   lin_desc.lin_cmd = SUBSCRIBE;
   lin_desc.uc_status = 0;
   lin_desc.uc_pt_data = lin_data_node;
   lin_desc.pt_function = lin_slave_task_ID12;
   lin_register_desciptor(LIN_MASTER_NODE_NUM, 0, &lin_desc);

   NVIC_EnableIRQ(USART0_IRQn);
   usart_enable_interrupt(USART0, US_IER_LINID);

Workflow

1. LIN slave node ID:

   #define LIN_FRAME_ID_12    0x12

2. Specific data to flash the LED:

   #define LIN_SPECIFIC_BYTE    0x55

3. Slave node number:

   #define LIN_SLAVE_NODE_NUM 0

4. Initialize system clock:

   sysclk_init();

5. Initialize board peripherals:

   board_init();

6. Enable PMC for USART:

   pmc_enable_periph_clk(BOARD_ID_USART);

7. Initialize LIN master, set the master with baudrate 9600:

   lin_init( USART0, false, LIN_SLAVE_NODE_NUM, 9600, sysclk_get_cpu_hz());

8. Set LIN slave descriptor ID:

   lin_desc.uc_id = LIN_FRAME_ID_12;

9. Set LIN master descriptor transfer size:

   lin_desc.uc_dlc = sizeof(lin_data_node);

10. Set LIN slave transfer type SUBSCRIBE:

    lin_desc.lin_cmd = SUBSCRIBE;

11. Set LIN master default transfer status:

    lin_desc.uc_status = 0;

12. Set LIN slave transfer data buffer:

    lin_desc.uc_pt_data = lin_data_node;

13. Set LIN slave task handle:

    lin_desc.pt_function = lin_slave_task_ID12;

14. Setup the salve descriptor:

    lin_register_desciptor(LIN_SLAVE_NODE_NUM, 0, &lin_desc);

Use case

Example code

Add to application C-file:

void  lin_slave_task_ID12(uint8_t *uc_buf)
{
     if (uc_buf[0] == LIN_SPECIFIC_BYTE) {
                     LED_Toggle(LED0_GPIO);
             }
}

Workflow

1. The slave task is defined in the LIN descriptor.

   void  lin_slave_task_ID12(uint8_t *uc_buf)

2. Check if received the spcific byte and flash the LED.

   if (uc_buf[0] == LIN_SPECIFIC_BYTE) {
                   LED_Toggle(LED0_GPIO);
           }