基于stm32f4的三維旋轉(zhuǎn)顯示平臺

　　3.系統(tǒng)軟件設(shè)計

　　3.1軟件控制流程：

　　3.2關(guān)于實時生成體三維顯示數(shù)據(jù)的討論：

　　一個瓦片64*32

　　LED層FPGA*8：每個16*16LED

　　中間層stm32*2：每個4LED層的FPGA，也即32*32

　　由于經(jīng)過壓縮，一個led數(shù)據(jù)為4bits

　　所以一個stm32每一幀所要生成的數(shù)據(jù)為32*32*0.5bytes = 512bytes

　　轉(zhuǎn)速800轉(zhuǎn)，一幀1/800s = 1.25ms = 1250000ns

　　stm32f4主頻168Mhz，指令周期 = 5.93ns

　　約可執(zhí)行20萬多條指令

　　假設(shè)fsmc總線的速度為50Mhz，則每幀寫入的時間大概在0.02ms內(nèi)

　　程序總體思路

　　事先算出所有電子幀上非零的點，以及連續(xù)0的個數(shù)，在每一個電子幀同步后，算出生成下一幀的數(shù)據(jù)，寫入fifo

　　輸入：線段端點的集合

　　//input: endpoints of segments which formed the outline of a 3D model

　　//x position with range 0-95

　　//y position with range 0-95

　　//z position with range 0-128

　　/******************************************/

　　//from later discussion, one of the Q format

　　//type should replace the char type

　　/******************************************/

　　struct Coordinate_3D

　　{

　　_iq xPosition;

　　_iq yPosition;

　　_iq zPosition;

　　};

　　//after you get the intersection points in 3d coordinate, you need to remap it into 2d coordinate on the very electrical plane,

　　//and the conversion is quite simple Coordinate_2D.yPosition = Coordinate_3D.zPosition; Coordinate_2D.xPosition = sqrt(xPosition^2+yPosition^2)

　　struct Coordinate_2D

　　{

　　char xPosition;

　　char yPosition;

　　};

　　struct Line

　　{

　　struct Coordinate_3D beginPoint;

　　struct Coordinate_3D endPoint;

　　unsigned char color;

　　};

　　//frame structure to store the visible points in one electrical frame

　　//need to be discussed

　　//here's the prototype of the Frame structure, and basically the frame struture should contain the visible points,

　　//and the zero points. As we have enclosed the number of zero points after each visible points in their own data structure,

　　//only the number of zero points at the beginning of the whole frame should be enclosed in the frame struture

　　struct Frame

　　{

　　int zerosBefore;

　　PointQueue_t visiblePointQueue;

　　};

　　//we need a union structure like color plane with bit fields to store the color imformation of every four FPGAs in one data segment

　　//actually, it's a kind of frustrateing thing that we had to rebind the data into such an odd form.

　　union ColorPalette

　　{

　　struct

　　{

　　unsigned char color1 : 4;

　　unsigned char color2 : 4;

　　unsigned char color3 : 4;

　　unsigned char color3 : 4;

　　}distributedColor;

　　unsigned short unionColor;

　　};

　　//and now we need a complete point structure to sotre all the imformation above

　　//here we add a weight field = yPosition*96 + xPosition, which will facilitate

　　//our sort and calculation of the zero points number between each visible point

　　//it's important to understand that, 4 corresponding points on the LED panel

　　//will share one visiblepoint data structure.(一塊stm32負責(zé)4塊16*16的LED，每塊對應(yīng)的點的4位顏色信息，拼成16位的數(shù)據(jù)段)

　　struct VisiblePoint

　　{

　　struct Coordinate_2D coord;

　　union Colorplane ColorPalette;

　　int weight;

　　int zerosAfter;

　　};

　　//as now you can see, we need some thing to store the visible points array

　　typedef struct QueueNode

　　{

　　struct VisiblePoint pointData;

　　struct QueueNode * nextNode;

　　}QueueNode_t, *QueueNode_ptr;

　　typedef struct

　　{

　　QueueNode_ptr front;

　　QueueNode_ptr rear;

　　}PointQueue_t;

　　//finally, we will have 16*16 words(16 bits)to write into the fifo after each electrial frame sync cmd.

　　//it may hard for us to decide the frame structure now, let's see how will the work flow of the algorithm be.

　　//firstly, the overall function will be like this

　　void Real3DExt(struct Line inputLines[], int lineNumber, struct Frame outputFrames[])

　　//then we need some real implementation function to calculate the intersection points

　　//with 0 = no intersection points, 1 = only have one intersection points, 2 = the input line coincides the given electrical plane

　　//2 need to be treated as an exception

　　//the range of the degree is 0-359

　　//it's important to mention that each intersection point we calculate, we need to

　　//remap its coordinate from a 32*32 field to x,y = 0-15, as each stm32 only have a 32*32

　　//effective field(those intersection points out of this range belong to other stm32), which can be decided by its address

　　int InterCal(struct Line inputLine, struct VisiblePoint * outputPoint, int degree)

　　//so we will need something like this in the Real3DExt function:

　　for (int j = 0; j < 360; j++)

　　{

　　for(int i = 0; i < lineNumber; i++ )

　　InterCal(struct Line inputLine, struct VisiblePoint outputPoint, int degree);

　　......

　　}

　　/******************************************/

　　//simple float format version of InterCal

　　/******************************************/

　　//calculate formula

　　//Q = [-1,1,-1];

　　//P = [1,1,-1];

　　//V = Q - p = [-2,0,0];

　　//Theta = pi/6;

　　//Tmp0 = Q(1)*sin(Theta) - Q(2)*cos(Theta);

　　//Tmp1 = V(1)*sin(Theta) - V(2)*cos(Theta);

　　//Result = Q - (Tmp0/Tmp1)*V

　　float32_t f32_point0[3] = {-1.0f,1.0f,-1.0f};

　　float32_t f32_point1[3] = {1.0f,1.0f,-1.0f};

　　float32_t f32_directionVector[3], f32_normalVector[3], f32_theta,

　　f32_tmp0, f32_tmp1, f32_tmp2, f32_result[3];

　　arm_sub_f32(f32_point0,f32_point1,f32_directionVector,3);

　　f32_theta = PI/6.0f;

　　f32_normalVector[0] = arm_sin_f32(f32_theta);

　　f32_normalVector[1] = arm_cos_f32(f32_theta);

　　f32_normalVector[2] = 0.0f;

　　arm_dot_prod_f32(f32_point0, f32_normalVector, 3, &f32_tmp0);

　　arm_dot_prod_f32(f32_directionVector, f32_normalVector, 3, &f32_tmp1);

　　f32_tmp2 = f32_tmp0/f32_tmp1;

　　arm_scale_f32(f32_normalVector, f32_tmp2, f32_normalVector, 3);

　　arm_sub_f32(f32_point0, f32_normalVector, f32_result, 3);

　　//and than we need to decide whether to add a new visible point in the point queue, or to update

　　//the color field of a given point in the point queue(as 4 visible point share one data structure). from this point, you will find that, it may be

　　//sensible for you not to diretly insert a new point into the end of point queue but to insert it in order

　　//when you build the pointqueue. it seems more effective.

　　void EnPointQueue(PointQueue_t * inputQueue, QueueNode_t inputNode);

　　//finally we will get an sorted queue at the end of the inner for loop

　　//than we need to calculate the number of invisible points between these visible points

　　//and to store it in each frame structure. the main purpose to do so is to offer an quick generation

　　//of the blank point(color field = 16'b0) between each electrical frame

　　//the work flow will be like this:

　　loop

　　{

　　dma output of the blank points;

　　output of the visible points;

　　}

　　/******************************************/

　　//some points need more detailed discussion

　　/******************************************/

　　//1.memory allocation strategy

　　//a quite straight forward method will be establishing a big memnory pool in advance, but the drawback of this method

　　//is that it's hard for you to decide the size of the memory pool. Another way would be the C runtime library method,

　　// and you can use build-in function malloc to allocate the memory, but it will be a quite heavy load for the m3 cpu

　　// as you need dynamic memeory allocation throughout the algorithm.

　　//2.the choice of Q format of the IQMATH library

　　//from the discussion above, the range of the coordnate is about 1-100, but the range of sin&cos is only 0-1,so there's a large gap between them.

　　//may be we can choose iq24?? Simultaneously, another big problem will be the choice between IQMATH and arm dsp library as their q format is

　　//incompatible with each other. as far as my knowledge is concerned, we should choose IQMATH with m3 without fpu, and cmsis dsp library with m4 with fpu.

　　//more detail discussion about the range of the algorithm

　　//x,y range is -64 to 64

　　//the formula is

　　//Tmp0 = Q(1)*sin(Theta) - Q(2)*cos(Theta);

　　//Tmp0 range is -128 to 128

　　//Tmp1 = V(1)*sin(Theta) - V(2)*cos(Theta);

　　//Tmp1 range is -128 to 128

　　//Result = Q - (Tmp1/Tmp2)*V

　　//because the minimal precision of the coordinate is 1, so if the result of Tmp1/Tmp2 is bigger than 128, the Result will be

　　//saturated. With the same reson, if (Tmp1/Tmp2)*V >= 128 or <= -127, the result will be saturated

　　4.系統(tǒng)創(chuàng)新

　　其一，由于高效解析算法的提出，大幅簡化了真三維顯示器顯示數(shù)據(jù)的獲取難度，只需在PC端獲得當(dāng)前較為標(biāo)準(zhǔn)化的三維圖形的三角面頂點數(shù)據(jù)流文件，即可在真三維顯示平臺上顯示出來，使得真三維顯示器的整體顯示流程大為簡化。

　　其二，由于顯示體的結(jié)構(gòu)分為并行的若干區(qū)塊，各個區(qū)塊只顯示自身的部分，因此顯示屏幕的擴大并不會造成數(shù)據(jù)計算量的大幅增加，這就使得本顯示器的擴展性大大增強，可以適用于多種多樣的顯示范圍與領(lǐng)域。

　　其三，由于高效算法的優(yōu)化與區(qū)塊化顯示的優(yōu)勢，并行結(jié)構(gòu)的計算量相對較少，這就使得實時控制得以實現(xiàn)，大大增強了真三維顯示器的應(yīng)用領(lǐng)域。

　　其四，高效算法與區(qū)塊化顯示使得本三維體顯示器不需要如國內(nèi)外其他同類產(chǎn)品的中所需的高速傳輸方式，因此大大減少了從產(chǎn)品研發(fā)到材料再到加工中各個環(huán)節(jié)的成本。

　　5.評測與結(jié)論

　　在作品的過程中，我們發(fā)現(xiàn)本作品雖然還不是很成熟，也同樣具備較大的應(yīng)用前景與價值。價格成本的極大降低，使得真三維立體顯示的門檻很低，那么在一些對清晰度要求不高，但是希望多層次全角度呈現(xiàn)三維圖像的應(yīng)用領(lǐng)域，我們的真三維立體顯示器能發(fā)揮較大的作用。

　　附錄