1.先容GD32L233C采取的是一款M23的内核。这个芯片听说功耗非常的低，低到什么程度呢？等后面我们再进行测试，本日我们紧张来测试GD32L233C-START的DAC，既然要测试DAC，示波器是不可少的，这个实验在家做，然而LZ家里并没有示波器，不过最近看到一款好东西，LOTO虚拟示波器，看过这款示波器的参数，还不错。以是入手了一款，丈量芯片输出的DAC该当没什么问题，接下来开始测试吧。2.设计首先须要输出让芯片输出DAC，而且还须要输出波形，这个轻微费点功夫，之前在GD32L233C-START移植了RTThread，现在在这个代码的根本上添加DAC的输出程序，这个程序移植了其他网友的，代码我也贴出来，经由测试，代码没有啥问题：比较麻烦的是正弦波的代码：
const float sinus_I_quarter[91] ={ 0.0000, 0.0175, 0.0349, 0.0523, 0.0698, 0.0872, 0.1045, 0.1219, 0.1392, 0.1564, // 00 .. 09 0.1736, 0.1908, 0.2079, 0.2250, 0.2419, 0.2588, 0.2756, 0.2924, 0.3090, 0.3256, // 10 .. 19 0.3420, 0.3584, 0.3746, 0.3907, 0.4067, 0.4226, 0.4384, 0.4540, 0.4695, 0.4848, // 20 .. 29 0.5000, 0.5150, 0.5299, 0.5446, 0.5592, 0.5736, 0.5878, 0.6018, 0.6157, 0.6293, // 30 .. 39 0.6428, 0.6561, 0.6691, 0.6820, 0.6947, 0.7071, 0.7193, 0.7314, 0.7431, 0.7547, // 40 .. 49 0.7660, 0.7771, 0.7880, 0.7986, 0.8090, 0.8192, 0.8290, 0.8387, 0.8480, 0.8572, // 50 .. 59 0.8660, 0.8746, 0.8829, 0.8910, 0.8988, 0.9063, 0.9135, 0.9205, 0.9272, 0.9336, // 60 .. 69 0.9397, 0.9455, 0.9511, 0.9563, 0.9613, 0.9659, 0.9703, 0.9744, 0.9781, 0.9816, // 70 .. 79 0.9848, 0.9877, 0.9903, 0.9925, 0.9945, 0.9962, 0.9976, 0.9986, 0.9994, 0.9998, // 80 .. 89 1.0000 // 90};#define CIRCLE_QUARTER_1 1#define CIRCLE_QUARTER_2 2#define CIRCLE_QUARTER_3 3#define CIRCLE_QUARTER_4 4float sinus_lookup (unsigned int angle){ float sin_value; unsigned int circle_quarter; // correct angles outside the accepted angle range into 0 .. 359 if (angle > 359u) angle = angle % 360u; circle_quarter = 1 + (angle / 90u); switch (circle_quarter) { case CIRCLE_QUARTER_1: // 00 .. 89 sin_value = sinus_I_quarter[angle]; break; case CIRCLE_QUARTER_2: // 90 .. 179 sin_value = sinus_I_quarter[180 - angle]; break; case CIRCLE_QUARTER_3: // 180 .. 269 sin_value = -sinus_I_quarter[angle - 180]; break; case CIRCLE_QUARTER_4: // 270 .. 359 sin_value = -sinus_I_quarter[360 - angle]; break; } return sin_value;}void plot_sin(uint32_t f, uint32_t delta_f){ / 定时周期为T=1/delta_f， f=1/(pMaxT) / static uint32_t point = 0; uint32_t pMAX = delta_f/f; uint32_t value = 0; if (point++ > pMAX) point = 0; value = (uint32_t)((sinus_lookup(360point/pMAX)+1)10000)2047/10000; dac_software_trigger_enable(); dac_data_set(DAC_ALIGN_12B_R, value);}
接下来是锯齿波和方波的代码，这两个代码比较大略：
void plot_triangle(uint32_t f, uint32_t delta_f){ / 定时周期为T=1/delta_f， f=1/(pMaxT) / static uint32_t point = 0; uint32_t pMAX = delta_f/f; uint32_t pMAX2 = pMAX/2; uint32_t value = 0; if (++point > pMAX) point = 0; if (point < pMAX2) { value = point 4095 / pMAX2; } else { value = (pMAX - point) 4095 / pMAX2; } dac_software_trigger_enable(); dac_data_set(DAC_ALIGN_12B_R, value);}void plot_square(uint32_t f, uint32_t delta_f){ / 定时周期为T=1/delta_f， f=1/(pMaxT) / static uint32_t point = 0; uint32_t pMAX = delta_f/f; uint32_t pMAX2 = pMAX/2; uint32_t value = 0; if (++point > pMAX) point = 0; if (point < pMAX2) { value = 0; } else { value = 0xFFF; } dac_software_trigger_enable(); dac_data_set(DAC_ALIGN_12B_R, value);}
末了须要开启一个定时器，还有DAC的初始化：
void timerx_init(uint32_t timer_periph, uint16_t period, uint16_t prescaler){ / TIMER1 configuration: input capture mode ------------------- the external signal is connected to TIMER1 CH0 pin (PA0) the rising edge is used as active edge the TIMER1 CH0CV is used to compute the frequency value ------------------------------------------------------------ / timer_parameter_struct timer_initpara; timer_ic_parameter_struct timer_icinitpara; / enable the peripherals clock / rcu_periph_clock_enable(RCU_TIMER2); / deinit a TIMER / timer_deinit(timer_periph); / initialize TIMER init parameter struct / timer_struct_para_init(&timer_initpara); / TIMER1 configuration / timer_initpara.prescaler = prescaler; timer_initpara.alignedmode = TIMER_COUNTER_EDGE; timer_initpara.counterdirection = TIMER_COUNTER_UP; timer_initpara.period = period; timer_initpara.clockdivision = TIMER_CKDIV_DIV1; timer_init(timer_periph, &timer_initpara); / TIMER1 CH0 input capture configuration / timer_icinitpara.icpolarity = TIMER_IC_POLARITY_RISING; timer_icinitpara.icselection = TIMER_IC_SELECTION_DIRECTTI; timer_icinitpara.icprescaler = TIMER_IC_PSC_DIV1; timer_icinitpara.icfilter = 0x00; timer_input_capture_config(timer_periph, TIMER_CH_0, &timer_icinitpara); / auto-reload preload enable / timer_auto_reload_shadow_enable(timer_periph); / clear channel 0 interrupt bit / timer_interrupt_flag_clear(timer_periph, TIMER_INT_CH0); / channel 0 interrupt enable / timer_interrupt_enable(timer_periph, TIMER_INT_CH0); / enable a TIMER / timer_enable(timer_periph);}#define DAC_WAVE_TESTvoid timer2_init(void){ timer_deinit(TIMER2); rcu_periph_clock_enable(RCU_TIMER2);#ifdef DAC_WAVE_TEST timerx_init(TIMER2, 639, 9); // 100KHz 0.1ms#endif timer_interrupt_enable(TIMER2, TIMER_INT_UP); nvic_irq_enable(TIMER2_IRQn, 3);}void TIMER2_IRQHandler(void){#ifdef DAC_WAVE_TEST plot_sin(100, 10000); //正弦波 //plot_triangle(1, 10000); //锯齿波 //plot_square(1, 10000); //方波#endif timer_interrupt_flag_clear(TIMER2, TIMER_INT_FLAG_UP);}void dac1_init(void){ rcu_periph_clock_enable(RCU_GPIOA); rcu_periph_clock_enable(RCU_DAC); gpio_mode_set(GPIOA, GPIO_MODE_ANALOG, GPIO_PUPD_NONE, GPIO_PIN_4); dac_deinit(); / software trigger / dac_trigger_enable(); dac_trigger_source_config(DAC_TRIGGER_SOFTWARE); / no noise wave / dac_wave_mode_config(DAC_WAVE_DISABLE); / noise wave - triangle / //dac_wave_mode_config(DAC_WAVE_MODE_TRIANGLE); //dac_triangle_noise_config(DAC_TRIANGLE_AMPLITUDE_4095); / noise wave - lfsr / //dac_wave_mode_config(DAC_WAVE_MODE_LFSR); //dac_lfsr_noise_config(DAC_LFSR_BITS11_0); dac_output_buffer_enable(); / enable DAC and set data / dac_enable(); dac_software_trigger_enable(); dac_data_set(DAC_ALIGN_12B_R, 0);}
这样就可以输出正弦波、锯齿波和方波了。3.波形丈量接下来我们来看一下输出的波形是否符合哀求，首先须要将【GD32L233C-START】开拓板连接LOTO示波器，分别连接GND和PA4管教，连接效果图如下图1所示。
图1
然后让DAC输出正弦波，看一下波形如何。
图2
从上图2中可以看到，一个周期大约在10ms，以是正弦波的周期为100Hz，输出还是听精准的。然后输出锯齿波看看波形如何。
图3
从上图3可以得出，锯齿波的波形频率为1Hz。末了我们来看看方波的波形图如何。
图4
从上图4可以看到，方波的波形频率为1Hz。从上面波形可以得出，【GD32L233C-START】的定时器比较精准，DAC的输出值也比较稳定，性能还是不错的！
4.总结刚入手的LOTO示波器还不错，丈量的精度挺高的，不过还有好多设置没弄明白，等后续多琢磨琢磨。做电子的示波器是必不可少的，我先替你们测试测试这个示波器如何。GD32L233C是新出来的芯片，整体功能还须要多进行测试，它最突出的低功耗后续要好好丈量一下，这次就先到这里了。
