To configure a CAN bus interface, a global (optional: const) variable of the type CANBUS_PARA (defined in can_bus.h) must be allocated in the configuration file can_cfg.c, and filled with the corresponding configuration values.
CAN Bus Interface Config
The RX600 CAN Driver will be used as an example to describe the communication parameters required in can_cfg.c.
#include "can_bus.h"
const CANBUS_PARA CanCfg = { /* --------------- CAN BUS CONFIGURATION -------------- */
CAN_FALSE, [1] /* EXTENDED FLAG */
1000000L, [2] /* BAUDRATE */
0, [3] /* BUS NODE */
0, [4] /* BUS DEVICE */
[5] /* DRIVER FUNCTIONS */
RX600_CAN_Init, /* Init */
RX600_CAN_Open, /* Open */
RX600_CAN_Close, /* Close */
RX600_CAN_IoCtl, /* IoCtl */
RX600_CAN_Read, /* Read */
RX600_CAN_Write, /* Write */
{ /* DRIVER IO FUNCTION CODES */
IO_RX600_CAN_SET_BAUDRATE, [6] /* Set Baud Rate */
IO_RX600_CAN_START, /* Start */
IO_RX600_CAN_STOP, /* Stop */
IO_RX600_CAN_RX_STANDARD, /* Rx Standard */
IO_RX600_CAN_RX_EXTENDED, /* Rx Extended */
IO_RX600_CAN_TX_READY, /* Tx Ready */
IO_RX600_CAN_GET_NODE_STATUS, /* Get Node Status */
}
};
- A CAN Bus Configuration
MUST
- be declared global because the configuration data will be used both during initialization and in the CAN Bus Layer. Also, it is done this way to save RAM Space and get a write-protected configuration.
Node & Device Separation
A separation of Bus Node from Device Driver is necessary when different CAN modules are used (i.e. on a processor with integrated CAN module and also external CAN module(s), or with a CAN module with multiple channels).
Example
The MPC565 processor TouCAN has 3 available CAN channles (A, B, C) with the option of also having 3 external SJA1000 CAN modules, having 6 CAN Nodes overall available. However, both the device driver(s) from TouCAN & SJA1000 range from 0-2, and since each CAN node must have it's own unique Bus Node/Driver Device configuration, the following shows a possible configuration of the 6 CAN nodes:
Configuration TouCAN A |
Configuration TouCAN B |
Configuration TouCAN C |
Configuration SJA1000 1 |
Configuration SJA1000 2 |
Configuration SJA1000 3 |
If only one CAN device is used then both the bus node and driver device can be set to equal values.