Get best of the week

我如何拒绝计算平方根



通常，在对信号进行数字处理时，有必要计算向量的长度，通常这可以通过公式A = SQRT（X ^ 2 + Y ^ 2）完成。在这里对值进行平方并不困难，但是计算平方根的操作并不是简单的操作，尤其是对于微控制器而言。另外，根计算算法随着时间的流逝是不稳定的，并且对于其中有许多这样的计算的算法，难以预测计算所需的时间。

我也面临这样的问题。关于我如何拒绝计算根的过程，请阅读下文。

首先，考虑四个向量，它们位于不同的区域。



我们将把一切减少到四分之一-减少到第一。为此，取Y坐标，如果它为负，则将其变为正。如果已经是积极的，那么我们将保持一切不变。

实际上，由于我具有以无符号整数表示的绝对坐标和值，因此我们计算模块。

如果Y> 2047，则Y = Y-2047
如果Y <= 2047，则Y = 2047-Y。

这里2047是一个虚拟零，因为当我发明这辆自行车时，我参与的项目有12位ADC。

让我们看看发生什么了。



我们将对坐标X进行同样的操作。

如果X> 2047，则X = X-2047
如果X <= 2047，则X = 2047-X

顺便说一下，值得注意的是，从两个12位值中，有两个11位值。



现在所有向量都在第一季度，但我们正在寻找的长度没有改变。

转换的下一个阶段：“绕45度轴扭转”。

向量的角度可以从零到90度，而如果向量Y> X的坐标中，向量的角度在45-90度的范围内，如果Y <X，则向量的角度小于45度。好吧，如果X = Y，则矢量的角度为45度。

将向量减少到45度。

如果Y> X，则TEMP = Y，Y = X，X = TEMP（在位置交换X和Y）。
如果Y <= X，则我们什么也不做。

我们看看发生了什么。所有向量都在0到45度的角度范围内。



我想指出的是，在此阶段，我想到将角度检查为22.5度并再次部署。然后检查并扭转12.25度。依此类推，直到向量“位于” X轴上，然后其长度将由X坐标确定，并且Y将变为零。

但是我没有这样走，我押注了另一种方法，后来证明，我没有输。

如果将Y除以X，然后从该商中取反正切，则将获得角度。如果将X除以该角度的余弦，就可以得到向量的长度。

因此，向量的长度为A = X / COS（ATAN（Y / X））

当我认为需要从反正切表中获取角度，然后从余弦表中获取系数时，这似乎很困难。

但是什么也没发生。我决定，您可以立即创建一个表，其中Y / X比率用于处理单元格，并且在其中存在系数，必须将X除以该系数以获得向量的长度。

A = X / K; 其中K = COS（ATAN（Y / X））

但乘法比除法容易，因此：

A = X * K; 其中K = 1 / COS（ATAN（Y / X））

很明显，对于所有（Y / X），所有K都必须预先计算。

计算表包含2048个值，每个值为16位。那就是4kB的数据。

表
Magnitude_Table
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800,0x0800
DCW 0x0801,0x0801,0x0801,0x0801,0x0801,0x0801,0x0801,0x0801
DCW 0x0801,0x0801,0x0801,0x0801,0x0801,0x0801,0x0801,0x0801
DCW 0x0801,0x0801,0x0801,0x0801,0x0801,0x0801,0x0801,0x0801
DCW 0x0801,0x0801,0x0802,0x0802,0x0802,0x0802,0x0802,0x0802
DCW 0x0802,0x0802,0x0802,0x0802,0x0802,0x0802,0x0802,0x0802
DCW 0x0802,0x0802,0x0802,0x0802,0x0802,0x0802,0x0803,0x0803
DCW 0x0803,0x0803,0x0803,0x0803,0x0803,0x0803,0x0803,0x0803
DCW 0x0803,0x0803,0x0803,0x0803,0x0803,0x0803,0x0803,0x0803
DCW 0x0804,0x0804,0x0804,0x0804,0x0804,0x0804,0x0804,0x0804
DCW 0x0804,0x0804,0x0804,0x0804,0x0804,0x0804,0x0804,0x0805
DCW 0x0805,0x0805,0x0805,0x0805,0x0805,0x0805,0x0805,0x0805
DCW 0x0805,0x0805,0x0805,0x0805,0x0806,0x0806,0x0806,0x0806
DCW 0x0806,0x0806,0x0806,0x0806,0x0806,0x0806,0x0806,0x0806
DCW 0x0806,0x0807,0x0807,0x0807,0x0807,0x0807,0x0807,0x0807
DCW 0x0807,0x0807,0x0807,0x0807,0x0807,0x0808,0x0808,0x0808
DCW 0x0808,0x0808,0x0808,0x0808,0x0808,0x0808,0x0808,0x0808
DCW 0x0809,0x0809,0x0809,0x0809,0x0809,0x0809,0x0809,0x0809
DCW 0x0809,0x0809,0x080A,0x080A,0x080A,0x080A,0x080A,0x080A
DCW 0x080A,0x080A,0x080A,0x080A,0x080B,0x080B,0x080B,0x080B
DCW 0x080B,0x080B,0x080B,0x080B,0x080B,0x080B,0x080C,0x080C
DCW 0x080C,0x080C,0x080C,0x080C,0x080C,0x080C,0x080C,0x080D
DCW 0x080D,0x080D,0x080D,0x080D,0x080D,0x080D,0x080D,0x080E
DCW 0x080E,0x080E,0x080E,0x080E,0x080E,0x080E,0x080E,0x080E
DCW 0x080F,0x080F,0x080F,0x080F,0x080F,0x080F,0x080F,0x080F
DCW 0x0810,0x0810,0x0810,0x0810,0x0810,0x0810,0x0810,0x0810
DCW 0x0811,0x0811,0x0811,0x0811,0x0811,0x0811,0x0811,0x0811
DCW 0x0812,0x0812,0x0812,0x0812,0x0812,0x0812,0x0812,0x0813
DCW 0x0813,0x0813,0x0813,0x0813,0x0813,0x0813,0x0814,0x0814
DCW 0x0814,0x0814,0x0814,0x0814,0x0814,0x0814,0x0815,0x0815
DCW 0x0815,0x0815,0x0815,0x0815,0x0816,0x0816,0x0816,0x0816
DCW 0x0816,0x0816,0x0816,0x0817,0x0817,0x0817,0x0817,0x0817
DCW 0x0817,0x0817,0x0818,0x0818,0x0818,0x0818,0x0818,0x0818
DCW 0x0819,0x0819,0x0819,0x0819,0x0819,0x0819,0x0819,0x081A
DCW 0x081A,0x081A,0x081A,0x081A,0x081A,0x081B,0x081B,0x081B
DCW 0x081B,0x081B,0x081B,0x081C,0x081C,0x081C,0x081C,0x081C
DCW 0x081C,0x081D,0x081D,0x081D,0x081D,0x081D,0x081D,0x081E
DCW 0x081E,0x081E,0x081E,0x081E,0x081E,0x081F,0x081F,0x081F
DCW 0x081F,0x081F,0x081F,0x0820,0x0820,0x0820,0x0820,0x0820
DCW 0x0820,0x0821,0x0821,0x0821,0x0821,0x0821,0x0822,0x0822
DCW 0x0822,0x0822,0x0822,0x0822,0x0823,0x0823,0x0823,0x0823
DCW 0x0823,0x0824,0x0824,0x0824,0x0824,0x0824,0x0824,0x0825
DCW 0x0825,0x0825,0x0825,0x0825,0x0826,0x0826,0x0826,0x0826
DCW 0x0826,0x0827,0x0827,0x0827,0x0827,0x0827,0x0828,0x0828
DCW 0x0828,0x0828,0x0828,0x0829,0x0829,0x0829,0x0829,0x0829
DCW 0x082A,0x082A,0x082A,0x082A,0x082A,0x082B,0x082B,0x082B
DCW 0x082B,0x082B,0x082C,0x082C,0x082C,0x082C,0x082C,0x082D
DCW 0x082D,0x082D,0x082D,0x082D,0x082E,0x082E,0x082E,0x082E
DCW 0x082E,0x082F,0x082F,0x082F,0x082F,0x0830,0x0830,0x0830
DCW 0x0830,0x0830,0x0831,0x0831,0x0831,0x0831,0x0831,0x0832
DCW 0x0832,0x0832,0x0832,0x0833,0x0833,0x0833,0x0833,0x0833
DCW 0x0834,0x0834,0x0834,0x0834,0x0835,0x0835,0x0835,0x0835
DCW 0x0835,0x0836,0x0836,0x0836,0x0836,0x0837,0x0837,0x0837
DCW 0x0837,0x0837,0x0838,0x0838,0x0838,0x0838,0x0839,0x0839
DCW 0x0839,0x0839,0x083A,0x083A,0x083A,0x083A,0x083A,0x083B
DCW 0x083B,0x083B,0x083B,0x083C,0x083C,0x083C,0x083C,0x083D
DCW 0x083D,0x083D,0x083D,0x083E,0x083E,0x083E,0x083E,0x083F
DCW 0x083F,0x083F,0x083F,0x0840,0x0840,0x0840,0x0840,0x0840
DCW 0x0841,0x0841,0x0841,0x0841,0x0842,0x0842,0x0842,0x0842
DCW 0x0843,0x0843,0x0843,0x0843,0x0844,0x0844,0x0844,0x0844
DCW 0x0845,0x0845,0x0845,0x0845,0x0846,0x0846,0x0846,0x0847
DCW 0x0847,0x0847,0x0847,0x0848,0x0848,0x0848,0x0848,0x0849
DCW 0x0849,0x0849,0x0849,0x084A,0x084A,0x084A,0x084A,0x084B
DCW 0x084B,0x084B,0x084B,0x084C,0x084C,0x084C,0x084D,0x084D
DCW 0x084D,0x084D,0x084E,0x084E,0x084E,0x084E,0x084F,0x084F
DCW 0x084F,0x0850,0x0850,0x0850,0x0850,0x0851,0x0851,0x0851
DCW 0x0851,0x0852,0x0852,0x0852,0x0853,0x0853,0x0853,0x0853
DCW 0x0854,0x0854,0x0854,0x0854,0x0855,0x0855,0x0855,0x0856
DCW 0x0856,0x0856,0x0856,0x0857,0x0857,0x0857,0x0858,0x0858
DCW 0x0858,0x0858,0x0859,0x0859,0x0859,0x085A,0x085A,0x085A
DCW 0x085A,0x085B,0x085B,0x085B,0x085C,0x085C,0x085C,0x085C
DCW 0x085D,0x085D,0x085D,0x085E,0x085E,0x085E,0x085F,0x085F
DCW 0x085F,0x085F,0x0860,0x0860,0x0860,0x0861,0x0861,0x0861
DCW 0x0861,0x0862,0x0862,0x0862,0x0863,0x0863,0x0863,0x0864
DCW 0x0864,0x0864,0x0864,0x0865,0x0865,0x0865,0x0866,0x0866
DCW 0x0866,0x0867,0x0867,0x0867,0x0868,0x0868,0x0868,0x0868
DCW 0x0869,0x0869,0x0869,0x086A,0x086A,0x086A,0x086B,0x086B
DCW 0x086B,0x086C,0x086C,0x086C,0x086C,0x086D,0x086D,0x086D
DCW 0x086E,0x086E,0x086E,0x086F,0x086F,0x086F,0x0870,0x0870
DCW 0x0870,0x0871,0x0871,0x0871,0x0872,0x0872,0x0872,0x0873
DCW 0x0873,0x0873,0x0874,0x0874,0x0874,0x0874,0x0875,0x0875
DCW 0x0875,0x0876,0x0876,0x0876,0x0877,0x0877,0x0877,0x0878
DCW 0x0878,0x0878,0x0879,0x0879,0x0879,0x087A,0x087A,0x087A
DCW 0x087B,0x087B,0x087B,0x087C,0x087C,0x087C,0x087D,0x087D
DCW 0x087D,0x087E,0x087E,0x087E,0x087F,0x087F,0x087F,0x0880
DCW 0x0880,0x0880,0x0881,0x0881,0x0881,0x0882,0x0882,0x0882
DCW 0x0883,0x0883,0x0883,0x0884,0x0884,0x0885,0x0885,0x0885
DCW 0x0886,0x0886,0x0886,0x0887,0x0887,0x0887,0x0888,0x0888
DCW 0x0888,0x0889,0x0889,0x0889,0x088A,0x088A,0x088A,0x088B
DCW 0x088B,0x088B,0x088C,0x088C,0x088D,0x088D,0x088D,0x088E
DCW 0x088E,0x088E,0x088F,0x088F,0x088F,0x0890,0x0890,0x0890
DCW 0x0891,0x0891,0x0892,0x0892,0x0892,0x0893,0x0893,0x0893
DCW 0x0894,0x0894,0x0894,0x0895,0x0895,0x0895,0x0896,0x0896
DCW 0x0897,0x0897,0x0897,0x0898,0x0898,0x0898,0x0899,0x0899
DCW 0x0899,0x089A,0x089A,0x089B,0x089B,0x089B,0x089C,0x089C
DCW 0x089C,0x089D,0x089D,0x089E,0x089E,0x089E,0x089F,0x089F
DCW 0x089F,0x08A0,0x08A0,0x08A1,0x08A1,0x08A1,0x08A2,0x08A2
DCW 0x08A2,0x08A3,0x08A3,0x08A4,0x08A4,0x08A4,0x08A5,0x08A5
DCW 0x08A5,0x08A6,0x08A6,0x08A7,0x08A7,0x08A7,0x08A8,0x08A8
DCW 0x08A9,0x08A9,0x08A9,0x08AA,0x08AA,0x08AA,0x08AB,0x08AB
DCW 0x08AC,0x08AC,0x08AC,0x08AD,0x08AD,0x08AE,0x08AE,0x08AE
DCW 0x08AF,0x08AF,0x08AF,0x08B0,0x08B0,0x08B1,0x08B1,0x08B1
DCW 0x08B2,0x08B2,0x08B3,0x08B3,0x08B3,0x08B4,0x08B4,0x08B5
DCW 0x08B5,0x08B5,0x08B6,0x08B6,0x08B7,0x08B7,0x08B7,0x08B8
DCW 0x08B8,0x08B9,0x08B9,0x08B9,0x08BA,0x08BA,0x08BB,0x08BB
DCW 0x08BB,0x08BC,0x08BC,0x08BD,0x08BD,0x08BD,0x08BE,0x08BE
DCW 0x08BF,0x08BF,0x08BF,0x08C0,0x08C0,0x08C1,0x08C1,0x08C1
DCW 0x08C2,0x08C2,0x08C3,0x08C3,0x08C3,0x08C4,0x08C4,0x08C5
DCW 0x08C5,0x08C5,0x08C6,0x08C6,0x08C7,0x08C7,0x08C8,0x08C8
DCW 0x08C8,0x08C9,0x08C9,0x08CA,0x08CA,0x08CA,0x08CB,0x08CB
DCW 0x08CC,0x08CC,0x08CD,0x08CD,0x08CD,0x08CE,0x08CE,0x08CF
DCW 0x08CF,0x08CF,0x08D0,0x08D0,0x08D1,0x08D1,0x08D2,0x08D2
DCW 0x08D2,0x08D3,0x08D3,0x08D4,0x08D4,0x08D4,0x08D5,0x08D5
DCW 0x08D6,0x08D6,0x08D7,0x08D7,0x08D7,0x08D8,0x08D8,0x08D9
DCW 0x08D9,0x08DA,0x08DA,0x08DA,0x08DB,0x08DB,0x08DC,0x08DC
DCW 0x08DD,0x08DD,0x08DD,0x08DE,0x08DE,0x08DF,0x08DF,0x08E0
DCW 0x08E0,0x08E0,0x08E1,0x08E1,0x08E2,0x08E2,0x08E3,0x08E3
DCW 0x08E4,0x08E4,0x08E4,0x08E5,0x08E5,0x08E6,0x08E6,0x08E7
DCW 0x08E7,0x08E7,0x08E8,0x08E8,0x08E9,0x08E9,0x08EA,0x08EA
DCW 0x08EB,0x08EB,0x08EB,0x08EC,0x08EC,0x08ED,0x08ED,0x08EE
DCW 0x08EE,0x08EF,0x08EF,0x08EF,0x08F0,0x08F0,0x08F1,0x08F1
DCW 0x08F2,0x08F2,0x08F3,0x08F3,0x08F3,0x08F4,0x08F4,0x08F5
DCW 0x08F5,0x08F6,0x08F6,0x08F7,0x08F7,0x08F8,0x08F8,0x08F8
DCW 0x08F9,0x08F9,0x08FA,0x08FA,0x08FB,0x08FB,0x08FC,0x08FC
DCW 0x08FD,0x08FD,0x08FD,0x08FE,0x08FE,0x08FF,0x08FF,0x0900
DCW 0x0900,0x0901,0x0901,0x0902,0x0902,0x0902,0x0903,0x0903
DCW 0x0904,0x0904,0x0905,0x0905,0x0906,0x0906,0x0907,0x0907
DCW 0x0908,0x0908,0x0908,0x0909,0x0909,0x090A,0x090A,0x090B
DCW 0x090B,0x090C,0x090C,0x090D,0x090D,0x090E,0x090E,0x090F
DCW 0x090F,0x0910,0x0910,0x0910,0x0911,0x0911,0x0912,0x0912
DCW 0x0913,0x0913,0x0914,0x0914,0x0915,0x0915,0x0916,0x0916
DCW 0x0917,0x0917,0x0918,0x0918,0x0918,0x0919,0x0919,0x091A
DCW 0x091A,0x091B,0x091B,0x091C,0x091C,0x091D,0x091D,0x091E
DCW 0x091E,0x091F,0x091F,0x0920,0x0920,0x0921,0x0921,0x0922
DCW 0x0922,0x0923,0x0923,0x0924,0x0924,0x0924,0x0925,0x0925
DCW 0x0926,0x0926,0x0927,0x0927,0x0928,0x0928,0x0929,0x0929
DCW 0x092A,0x092A,0x092B,0x092B,0x092C,0x092C,0x092D,0x092D
DCW 0x092E,0x092E,0x092F,0x092F,0x0930,0x0930,0x0931,0x0931
DCW 0x0932,0x0932,0x0933,0x0933,0x0934,0x0934,0x0935,0x0935
DCW 0x0936,0x0936,0x0937,0x0937,0x0938,0x0938,0x0939,0x0939
DCW 0x093A,0x093A,0x093B,0x093B,0x093C,0x093C,0x093D,0x093D
DCW 0x093E,0x093E,0x093F,0x093F,0x0940,0x0940,0x0941,0x0941
DCW 0x0942,0x0942,0x0943,0x0943,0x0944,0x0944,0x0945,0x0945
DCW 0x0946,0x0946,0x0947,0x0947,0x0948,0x0948,0x0949,0x0949
DCW 0x094A,0x094A,0x094B,0x094B,0x094C,0x094C,0x094D,0x094D
DCW 0x094E,0x094E,0x094F,0x094F,0x0950,0x0950,0x0951,0x0951
DCW 0x0952,0x0952,0x0953,0x0953,0x0954,0x0954,0x0955,0x0956
DCW 0x0956,0x0957,0x0957,0x0958,0x0958,0x0959,0x0959,0x095A
DCW 0x095A,0x095B,0x095B,0x095C,0x095C,0x095D,0x095D,0x095E
DCW 0x095E,0x095F,0x095F,0x0960,0x0960,0x0961,0x0961,0x0962
DCW 0x0962,0x0963,0x0964,0x0964,0x0965,0x0965,0x0966,0x0966
DCW 0x0967,0x0967,0x0968,0x0968,0x0969,0x0969,0x096A,0x096A
DCW 0x096B,0x096B,0x096C,0x096C,0x096D,0x096E,0x096E,0x096F
DCW 0x096F,0x0970,0x0970,0x0971,0x0971,0x0972,0x0972,0x0973
DCW 0x0973,0x0974,0x0974,0x0975,0x0976,0x0976,0x0977,0x0977
DCW 0x0978,0x0978,0x0979,0x0979,0x097A,0x097A,0x097B,0x097B
DCW 0x097C,0x097C,0x097D,0x097E,0x097E,0x097F,0x097F,0x0980
DCW 0x0980,0x0981,0x0981,0x0982,0x0982,0x0983,0x0983,0x0984
DCW 0x0985,0x0985,0x0986,0x0986,0x0987,0x0987,0x0988,0x0988
DCW 0x0989,0x0989,0x098A,0x098B,0x098B,0x098C,0x098C,0x098D
DCW 0x098D,0x098E,0x098E,0x098F,0x098F,0x0990,0x0991,0x0991
DCW 0x0992,0x0992,0x0993,0x0993,0x0994,0x0994,0x0995,0x0996
DCW 0x0996,0x0997,0x0997,0x0998,0x0998,0x0999,0x0999,0x099A
DCW 0x099A,0x099B,0x099C,0x099C,0x099D,0x099D,0x099E,0x099E
DCW 0x099F,0x099F,0x09A0,0x09A1,0x09A1,0x09A2,0x09A2,0x09A3
DCW 0x09A3,0x09A4,0x09A4,0x09A5,0x09A6,0x09A6,0x09A7,0x09A7
DCW 0x09A8,0x09A8,0x09A9,0x09AA,0x09AA,0x09AB,0x09AB,0x09AC
DCW 0x09AC,0x09AD,0x09AD,0x09AE,0x09AF,0x09AF,0x09B0,0x09B0
DCW 0x09B1,0x09B1,0x09B2,0x09B3,0x09B3,0x09B4,0x09B4,0x09B5
DCW 0x09B5,0x09B6,0x09B7,0x09B7,0x09B8,0x09B8,0x09B9,0x09B9
DCW 0x09BA,0x09BA,0x09BB,0x09BC,0x09BC,0x09BD,0x09BD,0x09BE
DCW 0x09BE,0x09BF,0x09C0,0x09C0,0x09C1,0x09C1,0x09C2,0x09C2
DCW 0x09C3,0x09C4,0x09C4,0x09C5,0x09C5,0x09C6,0x09C7,0x09C7
DCW 0x09C8,0x09C8,0x09C9,0x09C9,0x09CA,0x09CB,0x09CB,0x09CC
DCW 0x09CC,0x09CD,0x09CD,0x09CE,0x09CF,0x09CF,0x09D0,0x09D0
DCW 0x09D1,0x09D1,0x09D2,0x09D3,0x09D3,0x09D4,0x09D4,0x09D5
DCW 0x09D6,0x09D6,0x09D7,0x09D7,0x09D8,0x09D8,0x09D9,0x09DA
DCW 0x09DA,0x09DB,0x09DB,0x09DC,0x09DD,0x09DD,0x09DE,0x09DE
DCW 0x09DF,0x09DF,0x09E0,0x09E1,0x09E1,0x09E2,0x09E2,0x09E3
DCW 0x09E4,0x09E4,0x09E5,0x09E5,0x09E6,0x09E7,0x09E7,0x09E8
DCW 0x09E8,0x09E9,0x09E9,0x09EA,0x09EB,0x09EB,0x09EC,0x09EC
DCW 0x09ED,0x09EE,0x09EE,0x09EF,0x09EF,0x09F0,0x09F1,0x09F1
DCW 0x09F2,0x09F2,0x09F3,0x09F4,0x09F4,0x09F5,0x09F5,0x09F6
DCW 0x09F7,0x09F7,0x09F8,0x09F8,0x09F9,0x09FA,0x09FA,0x09FB
DCW 0x09FB,0x09FC,0x09FD,0x09FD,0x09FE,0x09FE,0x09FF,0x09FF
DCW 0x0A00,0x0A01,0x0A01,0x0A02,0x0A03,0x0A03,0x0A04,0x0A04
DCW 0x0A05,0x0A06,0x0A06,0x0A07,0x0A07,0x0A08,0x0A09,0x0A09
DCW 0x0A0A,0x0A0A,0x0A0B,0x0A0C,0x0A0C,0x0A0D,0x0A0D,0x0A0E
DCW 0x0A0F,0x0A0F,0x0A10,0x0A10,0x0A11,0x0A12,0x0A12,0x0A13
DCW 0x0A13,0x0A14,0x0A15,0x0A15,0x0A16,0x0A16,0x0A17,0x0A18
DCW 0x0A18,0x0A19,0x0A1A,0x0A1A,0x0A1B,0x0A1B,0x0A1C,0x0A1D
DCW 0x0A1D,0x0A1E,0x0A1E,0x0A1F,0x0A20,0x0A20,0x0A21,0x0A21
DCW 0x0A22,0x0A23,0x0A23,0x0A24,0x0A25,0x0A25,0x0A26,0x0A26
DCW 0x0A27,0x0A28,0x0A28,0x0A29,0x0A29,0x0A2A,0x0A2B,0x0A2B
DCW 0x0A2C,0x0A2D,0x0A2D,0x0A2E,0x0A2E,0x0A2F,0x0A30,0x0A30
DCW 0x0A31,0x0A32,0x0A32,0x0A33,0x0A33,0x0A34,0x0A35,0x0A35
DCW 0x0A36,0x0A36,0x0A37,0x0A38,0x0A38,0x0A39,0x0A3A,0x0A3A
DCW 0x0A3B,0x0A3B,0x0A3C,0x0A3D,0x0A3D,0x0A3E,0x0A3F,0x0A3F
DCW 0x0A40,0x0A40,0x0A41,0x0A42,0x0A42,0x0A43,0x0A44,0x0A44
DCW 0x0A45,0x0A45,0x0A46,0x0A47,0x0A47,0x0A48,0x0A49,0x0A49
DCW 0x0A4A,0x0A4B,0x0A4B,0x0A4C,0x0A4C,0x0A4D,0x0A4E,0x0A4E
DCW 0x0A4F,0x0A50,0x0A50,0x0A51,0x0A51,0x0A52,0x0A53,0x0A53
DCW 0x0A54,0x0A55,0x0A55,0x0A56,0x0A57,0x0A57,0x0A58,0x0A58
DCW 0x0A59,0x0A5A,0x0A5A,0x0A5B,0x0A5C,0x0A5C,0x0A5D,0x0A5D
DCW 0x0A5E,0x0A5F,0x0A5F,0x0A60,0x0A61,0x0A61,0x0A62,0x0A63
DCW 0x0A63,0x0A64,0x0A64,0x0A65,0x0A66,0x0A66,0x0A67,0x0A68
DCW 0x0A68,0x0A69,0x0A6A,0x0A6A,0x0A6B,0x0A6C,0x0A6C,0x0A6D
DCW 0x0A6D,0x0A6E,0x0A6F,0x0A6F,0x0A70,0x0A71,0x0A71,0x0A72
DCW 0x0A73,0x0A73,0x0A74,0x0A75,0x0A75,0x0A76,0x0A76,0x0A77
DCW 0x0A78,0x0A78,0x0A79,0x0A7A,0x0A7A,0x0A7B,0x0A7C,0x0A7C
DCW 0x0A7D,0x0A7E,0x0A7E,0x0A7F,0x0A80,0x0A80,0x0A81,0x0A81
DCW 0x0A82,0x0A83,0x0A83,0x0A84,0x0A85,0x0A85,0x0A86,0x0A87
DCW 0x0A87,0x0A88,0x0A89,0x0A89,0x0A8A,0x0A8B,0x0A8B,0x0A8C
DCW 0x0A8D,0x0A8D,0x0A8E,0x0A8E,0x0A8F,0x0A90,0x0A90,0x0A91
DCW 0x0A92,0x0A92,0x0A93,0x0A94,0x0A94,0x0A95,0x0A96,0x0A96
DCW 0x0A97,0x0A98,0x0A98,0x0A99,0x0A9A,0x0A9A,0x0A9B,0x0A9C
DCW 0x0A9C,0x0A9D,0x0A9E,0x0A9E,0x0A9F,0x0AA0,0x0AA0,0x0AA1
DCW 0x0AA1,0x0AA2,0x0AA3,0x0AA3,0x0AA4,0x0AA5,0x0AA5,0x0AA6
DCW 0x0AA7,0x0AA7,0x0AA8,0x0AA9,0x0AA9,0x0AAA,0x0AAB,0x0AAB
DCW 0x0AAC,0x0AAD,0x0AAD,0x0AAE,0x0AAF,0x0AAF,0x0AB0,0x0AB1
DCW 0x0AB1,0x0AB2,0x0AB3,0x0AB3,0x0AB4,0x0AB5,0x0AB5,0x0AB6
DCW 0x0AB7,0x0AB7,0x0AB8,0x0AB9,0x0AB9,0x0ABA,0x0ABB,0x0ABB
DCW 0x0ABC,0x0ABD,0x0ABD,0x0ABE,0x0ABF,0x0ABF,0x0AC0,0x0AC1
DCW 0x0AC1,0x0AC2,0x0AC3,0x0AC3,0x0AC4,0x0AC5,0x0AC5,0x0AC6
DCW 0x0AC7,0x0AC7,0x0AC8,0x0AC9,0x0AC9,0x0ACA,0x0ACB,0x0ACB
DCW 0x0ACC,0x0ACD,0x0ACD,0x0ACE,0x0ACF,0x0ACF,0x0AD0,0x0AD1
DCW 0x0AD1,0x0AD2,0x0AD3,0x0AD3,0x0AD4,0x0AD5,0x0AD5,0x0AD6
DCW 0x0AD7,0x0AD8,0x0AD8,0x0AD9,0x0ADA,0x0ADA,0x0ADB,0x0ADC
DCW 0x0ADC,0x0ADD,0x0ADE,0x0ADE,0x0ADF,0x0AE0,0x0AE0,0x0AE1
DCW 0x0AE2,0x0AE2,0x0AE3,0x0AE4,0x0AE4,0x0AE5,0x0AE6,0x0AE6
DCW 0x0AE7,0x0AE8,0x0AE8,0x0AE9,0x0AEA,0x0AEA,0x0AEB,0x0AEC
DCW 0x0AED,0x0AED,0x0AEE,0x0AEF,0x0AEF,0x0AF0,0x0AF1,0x0AF1
DCW 0x0AF2,0x0AF3,0x0AF3,0x0AF4,0x0AF5,0x0AF5,0x0AF6,0x0AF7
DCW 0x0AF7,0x0AF8,0x0AF9,0x0AF9,0x0AFA,0x0AFB,0x0AFC,0x0AFC
DCW 0x0AFD,0x0AFE,0x0AFE,0x0AFF,0x0B00,0x0B00,0x0B01,0x0B02
DCW 0x0B02,0x0B03,0x0B04,0x0B04,0x0B05,0x0B06,0x0B07,0x0B07
DCW 0x0B08,0x0B09,0x0B09,0x0B0A,0x0B0B,0x0B0B,0x0B0C,0x0B0D
DCW 0x0B0D,0x0B0E,0x0B0F,0x0B10,0x0B10,0x0B11,0x0B12,0x0B12
DCW 0x0B13,0x0B14,0x0B14,0x0B15,0x0B16,0x0B16,0x0B17,0x0B18
DCW 0x0B18,0x0B19,0x0B1A,0x0B1B,0x0B1B,0x0B1C,0x0B1D,0x0B1D
DCW 0x0B1E,0x0B1F,0x0B1F,0x0B20,0x0B21,0x0B22,0x0B22,0x0B23
DCW 0x0B24,0x0B24,0x0B25,0x0B26,0x0B26,0x0B27,0x0B28,0x0B28
DCW 0x0B29,0x0B2A,0x0B2B,0x0B2B,0x0B2C,0x0B2D,0x0B2D,0x0B2E
DCW 0x0B2F,0x0B2F,0x0B30,0x0B31,0x0B32,0x0B32,0x0B33,0x0B34
DCW 0x0B34,0x0B35,0x0B36,0x0B36,0x0B37,0x0B38,0x0B39,0x0B39
DCW 0x0B3A,0x0B3B,0x0B3B,0x0B3C,0x0B3D,0x0B3D,0x0B3E,0x0B3F
DCW 0x0B40,0x0B40,0x0B41,0x0B42,0x0B42,0x0B43,0x0B44,0x0B45
DCW 0x0B45,0x0B46,0x0B47,0x0B47,0x0B48,0x0B49,0x0B49,0x0B4A
DCW 0x0B4B,0x0B4C,0x0B4C,0x0B4D,0x0B4E,0x0B4E,0x0B4F,0x0B50

最小值为0x800h，表示2048。最早的值为0xB50，表示
2896。2896/2048 = 1.414，对应于1 / cos（45）。

要获得数组的索引，您需要将Y乘以2048并除以X。

所得的索引将指向数组的单元格，我们从该单元格中提取值，将X乘以该值并除以2048。结果是向量的长度。

我要指出的是，如果所使用的平台没有乘法和/或除法命令，则除以2048的除法和乘法是通过移位执行的，而另一个除法和乘法是由特殊的命令或算法执行的。

就我而言，使用的是STM32F103微控制器，该微控制器具有除法和乘法命令。

总结一下算法。

  1. 选中Y旁边的标志，并在必要时转动。
  2. 检查X上的标志，并在必要时转动。
  3. 比较X和Y，并在必要时交换位置。
  4. 检查X为0。
  5. 将Y乘以2048。
  6. X除以Y.
  7. 将结果值添加到数组的地址并读取值K。
  8. X乘以K。
  9. 将X除以2048除以移位。

产生的STM32F103汇编语言程序。

程序
	;r5 - X
	;r6 - Y

Magnitude
	mov32			r2,0x7FF
	mov32			r3,0x7FF
	cmp			r5,r2
	blo			Magnitude_xdn
Magnitude_xup
	sub			r5,r2
	b			Magnitude_X
Magnitude_xdn
	sub			r2,r5
	mov			r5,r2
Magnitude_X		;X in r5
	cmp			r6,r3
	blo			Magnitude_ydn
Magnitude_yup
	sub			r6,r3
	b			Magnitude_Y
Magnitude_ydn
	sub			r3,r6
	mov			r6,r3
Magnitude_Y		;Y in r6
	cmp			r5,r6
	blo			Magnitude_neg
Magnitude_pos
	mov			r1,r5
	mov			r5,r6
	mov			r6,r1
Magnitude_neg		;Rotating 45 degree
	cbz			r6,Magnitude_Zero
	lsl			r5,#0xC
	udiv			r5,r6
	mov32			r2,#0xFFFFFFFE
	and			r5,r2
	mov32			r2,Magnitude_Table
	add			r2,r5
	ldrh			r0,[r2]
	mul			r6,r0
	lsr			r6,#0xB
Magnitude_Zero
	pop			{lr}
	bx			lr
;In r6 length of vector


与上图所示的四个向量中的两个向量的经典方法相比，我将给出该算法的示例。

取蓝色矢量（从第三个区域开始）。

其坐标为X = -45，Y = -126（可以检查像素）

经典方法：

（-45）^ 2 +（-126）^ 2 = 2025 + 15876 = 17901
SQRT（17901）= 133（截断为整数）

算法：

X = 2047-45 = 2002，Y = 2047-126 = 1921

第1条：2002> 2047？ ->不行X = 2047-2002 = 45
点2：1921> 2047？ ->不行Y = 2047-1921 = 126
点3：126> 45->是。交换X = 126，Y = 45
点4：X = 0->否继续
第5段：Y = Y * 2048，Y = 45 * 2048 = 92160
点6：I = Y / X，I = 92160/126 = 731
要点7：在8个值的255行的表格中，我们正在寻找第731个值。
这是第91行和第3个值，即0x087e或十进制的2174
。
第8项：X = X * 2174，X = 126 * 2174 = 273924
项目9：A = X / 2048，A =2048分之273924= 133（截断为整数）

QED

现在取绿色矢量（从第四个区域开始）。

其坐标为X = -170，Y = 95（可以通过像素检查）。

经典方法：

（-170）^ 2 +（95）^ 2 = 28900 + 9025 = 37925
SQRT（37925）= 194（截断为整数）

算法：

X = 2047-170 = 1877，Y = 2047 + 95 = 2142

点1：1877> 2047？ ->不行X = 2047-1877 = 170
点2：2142> 2047？ ->是的。 Y = 2142-2047 = 95
点3：95 > 170->否。照原样离开。
点4：X = 0->否。继续
第5段：Y = Y * 2048，Y = 95 * 2048 = 194560
点6：I = Y / X，I = 194560/170 = 1144
点7：在表中，我们正在寻找第1144个值。
这是第143行和第0个值，即0x092A或十进制2346。
第8项：X = X * 2346，X = 2346 * 170 = 398820
项目9：A = X / 2048，A =二千〇四十八分之三十九万八千八百二十○= 194（截断为整数）

QED

总


可以在DSP中使用类似的算法（例如我），例如，您可以显着加速Fast Fourier Transform。它也可以用于使用光线跟踪的计算机图形学中。也许并且仍然有一个应用程序。

就这样。谢谢您的关注。

More articles:


All Articles