4 static lv_obj_t * chart1;  variable
91     lv_chart_set_next_value(chart1, ser1, lv_rand(20, 90));  in add_data()
93     if(cnt % 4 == 0) lv_chart_set_next_value(chart1, ser2, lv_rand(40, 60));  in add_data()
104     chart1 = lv_chart_create(lv_scr_act());  in lv_example_chart_2()
105     lv_obj_set_size(chart1, 200, 150);  in lv_example_chart_2()
106     lv_obj_center(chart1);  in lv_example_chart_2()
107     lv_chart_set_type(chart1, LV_CHART_TYPE_LINE);   /*Show lines and points too*/  in lv_example_chart_2()
109     lv_chart_set_div_line_count(chart1, 5, 7);  in lv_example_chart_2()
111     lv_obj_add_event_cb(chart1, draw_event_cb, LV_EVENT_DRAW_PART_BEGIN, NULL);  in lv_example_chart_2()
112     lv_chart_set_update_mode(chart1, LV_CHART_UPDATE_MODE_CIRCULAR);  in lv_example_chart_2()
115     ser1 = lv_chart_add_series(chart1, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y);  in lv_example_chart_2()
116     ser2 = lv_chart_add_series(chart1, lv_palette_main(LV_PALETTE_BLUE), LV_CHART_AXIS_SECONDARY_Y);  in lv_example_chart_2()
120         lv_chart_set_next_value(chart1, ser1, lv_rand(20, 90));  in lv_example_chart_2()
121         lv_chart_set_next_value(chart1, ser2, lv_rand(30, 70));  in lv_example_chart_2()