Custom_FIFO 结构在 user_define.h 中定义。图 2-6 中也展示了定义。

typedef struct {
    uint16_t fifo_in;
    uint16_t fifo_out;
    uint16_t fifo_count;
    Custom_Element *fifo_pointer;
} Custom_FIFO;

gCan2Spi_FIFO 和 gSpi2Can_FIFO 在 main.c 中定义。请注意 SRAM 的用法，它与 C2S_FIFO_SIZE、S2C_FIFO_SIZE 以及 Custom_Element 的大小有关。

/* Variables for C2S_FIFO
 * C2S_FIFO is used to temporarily store message from CAN to SPI */
Custom_Element gC2S_FIFO[C2S_FIFO_SIZE];
Custom_FIFO gCan2Spi_FIFO = {0, 0, 0, gC2S_FIFO};

/* Variables for S2C_FIFO
 * S2C_FIFO is used to temporarily store message from SPI to CAN */
Custom_Element gS2C_FIFO[S2C_FIFO_SIZE];
Custom_FIFO gSpi2Can_FIFO = {0, 0, 0, gS2C_FIFO};