RT-Thread-RealTouch触摸滤波算法优化RT-Thread问答社区

RealTouch触摸滤波算法优化

发布于 2012-12-08 01:09:34 浏览：8037 订阅该版

之前RealTouch使用的触摸屏滤波方法是连续采样10次AD值，然后去掉最大值和最小值后对其他8个值进行平均。但在实际使用中经常有漂移现象，下面是RealTouch之前使用的采样代码：
```            unsigned int i;
            rt_uint16_t tmpx[10];
            rt_uint16_t tmpy[10];
            uint8_t send_buffer[1];
            uint8_t recv_buffer[2];

for(i=0; i<10; i++)
            {
                send_buffer[0] = TOUCH_MSR_X;
                rt_spi_send_then_recv(touch->spi_device,
                                      send_buffer,
                                      1,
                                      recv_buffer,
                                      2);
                tmpx*  = (recv_buffer[0] & 0x7F) << 4;
                tmpx* |= (recv_buffer[1] >> 4) & 0x0F;

send_buffer[0] = TOUCH_MSR_Y;
                rt_spi_send_then_recv(touch->spi_device,
                                      send_buffer,
                                      1,
                                      recv_buffer,
                                      2);
                tmpy*  = (recv_buffer[0] & 0x7F) << 4;
                tmpy* |= (recv_buffer[1] >> 4) & 0x0F;
            }
            send_buffer[0] = 1 << 7;
            rt_spi_send(touch->spi_device, send_buffer, 1);

/* calculate average */
            {
                rt_uint32_t min_x = 0xFFFF, min_y = 0xFFFF;
                rt_uint32_t max_x = 0, max_y = 0;
                rt_uint32_t total_x = 0;
                rt_uint32_t total_y = 0;
                unsigned int i;

for(i=0; i<10; i++)
                {
                    if( tmpx* < min_x )
                    {
                        min_x = tmpx*;
                    }
                    if( tmpx* > max_x )
                    {
                        max_x = tmpx*;
                    }
                    total_x += tmpx*;

if( tmpy* < min_y )
                    {
                        min_y = tmpy*;
                    }
                    if( tmpy* > max_y )
                    {
                        max_y = tmpy*;
                    }
                    total_y += tmpy*;
                }
                total_x = total_x - min_x - max_x;
                total_y = total_y - min_y - max_y;
                touch->x = total_x / 8;
                touch->y = total_y / 8;```
这样子出现漂移现象比较多是因为在采样中如果有两个两个以上不正常的值存在将产生一定的误差。下面是改进的一种算法，主要是加入了一个阀门值的判断。进行8次AD采样，将得到的值用冒泡法进行从小到大排序，将排序好的第6个数据减去第3个数据，得到6号和3号之间的差值，在判断这个差值是否大于设定的阀门值，如果小于阀门值就视为有效值，将3,4,5,6这四组数据进行平均作为本次触摸的ADC值，否则重新采样。阀门值越小，采样判断越严格，通过率也会降低，这里设置为10，代码如下：
``` 
#define SAMP_CNT 8                                 //采用次数
#define SAMP_CNT_DIV2 4                         //中心值
#define SH   10                                        //阀值

uint8_t i, j, k, min;
	          uint16_t temp;
            rt_uint16_t tmpxy[2][SAMP_CNT];
            uint8_t send_buffer[1];
            uint8_t recv_buffer[2];
            for(i=0; i<SAMP_CNT; i++)
            {
                send_buffer[0] = TOUCH_MSR_X;
                rt_spi_send_then_recv(touch->spi_device,
                                      send_buffer,
                                      1,
                                      recv_buffer,
                                      2);
                tmpxy[0]*  = (recv_buffer[0] & 0x7F) << 4;
                tmpxy[1]* |= (recv_buffer[1] >> 4) & 0x0F;

send_buffer[0] = TOUCH_MSR_Y;
                rt_spi_send_then_recv(touch->spi_device,
                                      send_buffer,
                                      1,
                                      recv_buffer,
                                      2);
                tmpxy[1]*  = (recv_buffer[0] & 0x7F) << 4;
                tmpxy[1]* |= (recv_buffer[1] >> 4) & 0x0F;
            }
            send_buffer[0] = 1 << 7;
            rt_spi_send(touch->spi_device, send_buffer, 1);

/* calculate average */
						{
							rt_uint32_t total_x = 0;
              rt_uint32_t total_y = 0;
							for(k=0; k<2; k++)
							{ 
								// 冒泡法降序排列
								for(i=0; i<SAMP_CNT-1; i++)
								{
									min=i;
									for (j=i+1; j<SAMP_CNT; j++)
									{
										if (tmpxy[k][min] > tmpxy[k][j]) 
											min=j;
										}
										temp = tmpxy[k]*;
										tmpxy[k]* = tmpxy[k][min];
										tmpxy[k][min] = temp;
								}
							 //设定阈值
								if((tmpxy[k][SAMP_CNT_DIV2+1]-tmpxy[k][SAMP_CNT_DIV2-2]) > SH)
									{
										return;
									}
							}
				                  total_x=tmpxy[0][SAMP_CNT_DIV2-2]+tmpxy[0][SAMP_CNT_DIV2-1]+tmpxy[0][SAMP_CNT_DIV2]+tmpxy[0][SAMP_CNT_DIV2+1];
							 total_y=tmpxy[1][SAMP_CNT_DIV2-2]+tmpxy[1][SAMP_CNT_DIV2-1]+tmpxy[1][SAMP_CNT_DIV2]+tmpxy[1][SAMP_CNT_DIV2+1];
								// 求中间值的均值
								touch->x=total_x>>2;
								touch->y=total_y>>2;```
代码没有整理，比较乱，夜深了，睡觉去了~