韦东山ARM第一期作业（九）触摸屏

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01 - 作业所在路径

  ARM裸机1期加强版\源码文档图片\文档图片\第018课_ADC和触摸屏

02 - 作业描述

1. 百度搜索下载tslib库
2. 分析它的较准函数(不需要理解原理)、移植
3. tslib还有其他功能，比如判断连续点之间的距离，如果过大就丢弃。
   这可以解决我们程序中出现的问题：画线时突然有某个点在很远的距离出现

03 - 作业解答

  tslib库的运算量太大，有大量的浮点数乘除法运算，目前的裸版代码不支持，移植没有问题，只是计算出错，除法运算库不够强大
ts_calibrate.h

#ifndef _TSCALIBRATE_H
#define _TSCALIBRATE_H

typedef struct {
	int x[5], xfb[5];
	int y[5], yfb[5];
	int a[7];
} calibration;

int perform_calibration(calibration *cal);

#endif /* _TSCALIBRATE_H */

ts_calibrate.c

#include "../uart.h"
#include "ts_calibrate.h"

int perform_calibration(calibration *cal)
{
	int j;
	double n, x, y, x2, y2, xy, z, zx, zy;
	double det, a, b, c, e, f, i;
	double scaling = 65536.0;

	/* Get sums for matrix */
	n = x = y = x2 = y2 = xy = 0;
	for (j = 0; j < 5; j++) {
		n += 1.0;
		x += (double)cal->x[j];
		y += (double)cal->y[j];
		x2 += (double)(cal->x[j]*cal->x[j]);
		y2 += (double)(cal->y[j]*cal->y[j]);
		xy += (double)(cal->x[j]*cal->y[j]);
	}

	/* Get determinant of matrix -- check if determinant is too small */
	det = n*(x2*y2 - xy*xy) + x*(xy*y - x*y2) + y*(x*xy - y*x2);
	if (det < 0.1 && det > -0.1) {
		printf("ts_calibrate: determinant is too small -- %d\n\r", (int)det);
		return 0;
	}

	/* Get elements of inverse matrix */
	a = (x2*y2 - xy*xy)/det;
	b = (xy*y - x*y2)/det;
	c = (x*xy - y*x2)/det;
	e = (n*y2 - y*y)/det;
	f = (x*y - n*xy)/det;
	i = (n*x2 - x*x)/det;
	printf("abcefi:%d %d %d %d %d %d \r\n",a,b,c,e,f,i);

	/* Get sums for x calibration */
	z = zx = zy = 0;
	for (j = 0; j < 5; j++) {
		z += (double)cal->xfb[j];
		zx += (double)(cal->xfb[j]*cal->x[j]);
		zy += (double)(cal->xfb[j]*cal->y[j]);
	}

	/* Now multiply out to get the calibration for framebuffer x coord */
	cal->a[0] = (int)((a*z + b*zx + c*zy)*(scaling));
	cal->a[1] = (int)((b*z + e*zx + f*zy)*(scaling));
	cal->a[2] = (int)((c*z + f*zx + i*zy)*(scaling));

	printf("%d %d %d\n\r", (cal->a[0]),
			     (cal->a[1]),
			     (cal->a[2]));

	/* Get sums for y calibration */
	z = zx = zy = 0;
	for (j = 0; j < 5; j++) {
		z += (double)cal->yfb[j];
		zx += (double)(cal->yfb[j]*cal->x[j]);
		zy += (double)(cal->yfb[j]*cal->y[j]);
	}

	/* Now multiply out to get the calibration for framebuffer y coord */
	cal->a[3] = (int)((a*z + b*zx + c*zy)*(scaling));
	cal->a[4] = (int)((b*z + e*zx + f*zy)*(scaling));
	cal->a[5] = (int)((c*z + f*zx + i*zy)*(scaling));

	printf("%d %d %d\n\r", (cal->a[3]),
			     (cal->a[4]),
			     (cal->a[5]));

	/* If we got here, we're OK, so assign scaling to a[6] and return */
	cal->a[6] = (int)scaling;

	return 1;
}

  然后在原来代码tslib.c的ts_calibrate()函数中调用

	……
	if (g_ts_xy_swap)
	{
		/* 对调所有点的XY坐标 */
		swap_xy(&(cal.x[0]), &(cal.y[0]));
		swap_xy(&(cal.x[1]), &(cal.y[1]));
		swap_xy(&(cal.x[2]), &(cal.y[2]));
		swap_xy(&(cal.x[3]), &(cal.y[3]));
		swap_xy(&(cal.x[4]), &(cal.y[4]));
	}
	print_cal(&cal);
	/* 执行校准 */
	perform_calibration(&cal);
	//print_cal(&cal); //出错，计算错误
	……