6 应用代码

应用程序代码主要有两个部分。第一个是波形查询表 (LUT)。以下代码提供了 8 位峰值 256 点正弦波的表。此 DAC 查询表可利用在线计算器轻松生成。

/* Number of samples in the function array */
#define SINE_ARRAY_SAMPLES 256

/* Array of samples for function stored in flash */
const uint8_t gSineArray[SINE_ARRAY_SAMPLES] =
            {
            0x80,0x83,0x86,0x89,0x8c,0x8f,0x92,0x95,
            0x98,0x9c,0x9f,0xa2,0xa5,0xa8,0xab,0xae,
            0xb0,0xb3,0xb6,0xb9,0xbc,0xbf,0xc1,0xc4,
            0xc7,0xc9,0xcc,0xce,0xd1,0xd3,0xd5,0xd8,
            0xda,0xdc,0xde,0xe0,0xe2,0xe4,0xe6,0xe8,
            0xea,0xeb,0xed,0xef,0xf0,0xf2,0xf3,0xf4,
            0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfb,0xfc,
            0xfd,0xfd,0xfe,0xfe,0xfe,0xff,0xff,0xff,
            0xff,0xff,0xff,0xff,0xfe,0xfe,0xfd,0xfd,
            0xfc,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,0xf6,
            0xf5,0xf4,0xf2,0xf1,0xef,0xee,0xec,0xeb,
            0xe9,0xe7,0xe5,0xe3,0xe1,0xdf,0xdd,0xdb,
            0xd9,0xd7,0xd4,0xd2,0xcf,0xcd,0xca,0xc8,
            0xc5,0xc3,0xc0,0xbd,0xba,0xb8,0xb5,0xb2,
            0xaf,0xac,0xa9,0xa6,0xa3,0xa0,0x9d,0x9a,
            0x97,0x94,0x91,0x8e,0x8a,0x87,0x84,0x81,
            0x7e,0x7b,0x78,0x75,0x71,0x6e,0x6b,0x68,
            0x65,0x62,0x5f,0x5c,0x59,0x56,0x53,0x50,
            0x4d,0x4a,0x47,0x45,0x42,0x3f,0x3c,0x3a,
            0x37,0x35,0x32,0x30,0x2d,0x2b,0x28,0x26,
            0x24,0x22,0x20,0x1e,0x1c,0x1a,0x18,0x16,
            0x14,0x13,0x11,0x10,0xe,0xd,0xb,0xa,
            0x9,0x8,0x7,0x6,0x5,0x4,0x3,0x3,
            0x2,0x2,0x1,0x1,0x0,0x0,0x0,0x0,
            0x0,0x0,0x0,0x1,0x1,0x1,0x2,0x2,
            0x3,0x4,0x4,0x5,0x6,0x7,0x8,0x9,
            0xb,0xc,0xd,0xf,0x10,0x12,0x14,0x15,
            0x17,0x19,0x1b,0x1d,0x1f,0x21,0x23,0x25,
            0x27,0x2a,0x2c,0x2e,0x31,0x33,0x36,0x38,
            0x3b,0x3e,0x40,0x43,0x46,0x49,0x4c,0x4f,
            0x51,0x54,0x57,0x5a,0x5d,0x60,0x63,0x67,
            0x6a,0x6d,0x70,0x73,0x76,0x79,0x7c,0x80
            };

第二部分是配置 DMA 并启动计时器的主应用程序代码，如图 5-1所示。

int main(void)
{
    SYSCFG_DL_init();

    /* Configure DMA to load samples from the gSineArray to the CTL3 register of COMP_0_INST */
    DL_DMA_setSrcAddr(DMA, DMA_CH0_CHAN_ID, (uint32_t) &gSineArray[0]);
    DL_DMA_setDestAddr(DMA, DMA_CH0_CHAN_ID, (uint32_t) &COMP_0_INST->CTL3);
    DL_DMA_setTransferSize(DMA, DMA_CH0_CHAN_ID, SINE_ARRAY_SAMPLES);
    DL_DMA_setSubscriberChanID(DMA, DL_DMA_SUBSCRIBER_INDEX_0, 1);
    DL_DMA_enableChannel(DMA, DMA_CH0_CHAN_ID);

    /* Start the timer counting, the zero event of this timer acts as the trigger for transfer */
    DL_TimerG_startCounter(TIMER_0_INST);

    while (1) {
        __WFI();
    }
}