问题描述
我有一些代码可以通过VGA在屏幕上显示单个像素，但是在如何在屏幕上设置多个像素的位置上我有些固定.我设置了两个用于垂直同步和水平同步的计时器，然后使用垂直同步中断，根据我设置的 SetCompare 值，设置了一个标志，以允许PA8在正确的时间切换并输出像素.在计时器的频道上STM32f103c8也超频至128MHz.这是代码:
I have some code that displays a single pixel on screen through VGA but am a bit stuck on how I could set multiple pixels on screen where I want them. I set up two Timers for Vertical Sync and Horizontal Sync then using the V-Sync interrupt, I set a flag to allow PA8 to toggle and output a pixel at the correct timing based on the SetCompare value I set on the timer's channel. The STM32f103c8 is also overclocked to 128MHz. Here's the code:
#include "Arduino.h"
//640x480 at 60Hz
static volatile int vflag = 0;
void setup() {
#define FLASH_ACR (*(volatile uint32_t*)(0x40022000))
FLASH_ACR = 0b110010; //enable flash prefetch and wait state to increase stability at higher freq
pinMode(PA0, PWM); //31,468.75Hz (Horizontal Sync) (Channel 1)
Timer2.pause();
Timer2.setOverflow(4067); //reload register value
Timer2.setPrescaleFactor(1); //number that divides main clock
Timer2.setCompare(1, 488); //12% duty cycle (Syncpulse/Wholeline)
Timer2.setCompare(2, 2000); //0-4067 = vertical line going left or right respectively
Timer2.attachInterrupt(2, TRIGGER);
Timer2.refresh();
Timer2.resume();
pinMode(PA6, PWM); //60Hz (Vertical Sync) (Channel 1)
Timer3.pause();
Timer3.setOverflow(4183); //reload register value
Timer3.setPrescaleFactor(510); //number that divides main clock
Timer3.setCompare(1, 16); //0.38% duty cycle (Syncpulse/Wholeframe)
Timer3.setCompare(2, 2000); //0-4183 = horizontal line going up or down respectively
Timer3.attachInterrupt(2, TRIGGER2);
Timer3.refresh();
Timer3.resume();
pinMode(PA8, OUTPUT); //need to set PinMode in order for the ODR register to work
}
void loop() {
}
void TRIGGER(){
if(vflag==1){
__asm__ volatile (
"ldr r0, =(0x4001080C) \n\t" //GPIOA base address is 0x40010800 and ODR offset is 0x0C
"ldr r1, =(1<<8) \n\t" //turn on PA8
"ldr r2, =0 \n\t" //turn off PA8
"str r1, [r0] \n\t" //turn on PA8
"str r2, [r0] \n\t" //turn off PA8
);
vflag = 0; //we set the vflag back to zero when were done outputing pixels.
}
}
我了解存在图形缺陷/毛病，并且可以改进代码，但我尝试着眼于理论上这是如何工作的.我想做的是在屏幕上显示一个单词，该单词将由字母组成，而这些字母将由像素组组成.那么，最好的(或最简单的)对像素进行分组并在屏幕上多次执行的方法是什么呢?或者这通常是怎么做的?
I understand there's graphical defects/glitches and the code can be improved on but I'm trying to focus on how in theory this works. What I want to do is have a word display on screen, that word will be made up of letters, and those letters will be made up of groups of pixels. So then whats the best (or simplest) way to group pixels and execute them multiple times on-screen? Or how is this usually done?
推荐答案
我没有为 STM32 编写代码，所以即使代码对我来说看起来也不是，但是听起来您正在对各个像素进行硬编码带有计时器...并通过某些GPIO生成VGA信号.方法的这种组合对于用于可编程图形是有问题的.
I do not code for STM32 so even the code looks foreign to me however it sounds like you are hard-coding the individual pixels with timer... and generating VGA signal by some GPIO. That combination of methods is problematic to use for programmable graphics.
我正在使用 AVR32 ( UC3A ，其时钟要慢于您的时钟)来使用以下方法来制作VGA图像:
I am using AVR32 (UC3A with much slower clock then yours) to doing VGA image using:
-
屏幕缓冲区(视频)
简而言之，我已将整个屏幕图像存储在MCU存储器中.因此，您只需更改其内容即可，而无需更改VGA输出代码...
simply I have entire screen image stored in MCU memory. So you can simply change it contents without changing the VGA output code ...
问题是您需要有足够的存储空间来存储图像(以某种方式进行编码，以便可以直接传输到VGA连接器).我使用的AVR32具有16 + 32 + 32 KB的RAM，但是大多数MCU的RAM少得多(可以将静态图像存储在EPROM中，但是将无法更改图像输出).因此，如果您没有足够低的分辨率以适合内存或无法在系统中添加外部内存.
The problem is you need to have enough memory for the image (encoded in a way to enable direct transfer to VGA connector). I am using AVR32 with 16+32+32 KByte of RAM but most MCUs have much less RAM (static images can be stored in EPROM but then it would not be possible to change the image output). So in case you do not have enough either lower resolution to fit into memory or add external memory to your system.
使用集成的硬件外围设备生成VGA信号
我有更多版本的VGA信号生成可用:
I have more versions of VGA signal generation working:
- SDRAM ...使用MCU的SDRAM接口
- SMC ...使用MCU的SMC接口
- SSC ...使用同步串行接口
这一切都归结为将屏幕缓冲区复制到IO接口的 VGA点时钟(〜30MHz).然后在硬件方面，将用过的MCU引脚合并为VGA信号
It all boils down to copying the screen buffer to IO interface at the VGA dot clock (~30MHz). Then on HW side combining the used MCU pins into VGA signals
为了提高速度，您可以使用DMA.
for speed you can use DMA.
除此之外，您还需要生成同步信号，仅此而已.
On top of all this you need to generate the sync signals and that is all.
因此，请查看您的MCU数据表，找到能够以VGA点时钟速度同步传输至少3位数据(R，G，B)的接口.时钟离VGA点时钟越近越好(因为某些VGA监视器和LCD不能容忍太大的差异)
So look at your MCU datasheet and find interface capable of synchronous transfer at least 3 bit data (R,G,B) with VGA dot clock speed. The closer the clock is to VGA dot clock the better (as some VGA monitors and LCDs do not tolerate too big difference)
同步信号可以在视频内存中进行硬编码甚至编码.
the sync signals can be hardcoded or even encoded in the video ram.
最快的方法是使用串行接口，但是输出仅为B& W而不是RGB(除非您有3个SSC单位/通道)，但是您可以一次或直接通过DMA发送整个8/16/32像素，因此MCU有时间去做其他事情，并且需要更少的VRAM.
The fastest is to use serial interface but the output is just B&W instead of RGB (unless you got 3 SSC units/channels) however you can send entire 8/16/32 pixels at once or by DMA directly so the MCU has time for other stuff and also requires much less VRAM.
我最喜欢的是SDRAM接口(仅使用其数据总线)
My favourite is SDRAM interface (using just its data bus)
这里是我的系统的图像:
Here image from mine system:
矿井互连如下(使用MCU SDRAM接口版本):
Mine interconnection looks like this (using MCUs SDRAM interface version):
VGA <- AT32UC3A0512
R PX10 (EBI_D0)
G PX09 (EBI_D1)
B PX08 (EBI_D2)
Bright PX07 (EBI_D3)*
HS PA03
VS PA04
相关来源:
VGA_EBI_SDRAMC.h:
//------------------------------------------------------------------------------------------------
#define _PA_VGA_HS 8
#define _PA_VGA_VS 16
#define _PAmo 24
volatile avr32_gpio_port_t *port_PA=&GPIO.port[AVR32_PIN_PA00>>5];
volatile U8 *SDRAM=(U8*)AVR32_EBI_CS0_ADDRESS;
//------------------------------------------------------------------------------------------------
//--- VGA 640x480x4 60Hz -------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
#define VRAM_xs 304
#define VRAM_ys 400
#define VRAM_bs 4
#define VRAM_ls (VRAM_xs>>1)
U8 VRAM[VRAM_ls*VRAM_ys];
U8 VRAM_empty[VRAM_ls];
// Horizontal timing [us]
#define VGA_t0 3
#define VGA_t1 5
#define VGA_t2 32
// Vertikal timing [lines ~31.817us] aby voslo viac bodov tak je to natiahnute na 32us++
#define VGA_ys 525
#define VGA_VS 2
#define VGA_y0 (36+40)
#define VGA_y1 (VGA_y0+VRAM_ys)
//------------------------------------------------------------------------------------------------
void VGA_init();
void VGA_screen();
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
void VGA_init()
{
system_init();
Disable_global_interrupt();
gpio_configure_pins(port_PA,_PAmo,GPIO_DIR_OUTPUT|GPIO_INIT_HIGH);
static const gpio_map_t EBI_GPIO_MAP[] =
{
{ AVR32_EBI_DATA_0_PIN, AVR32_EBI_DATA_0_FUNCTION},
{ AVR32_EBI_DATA_1_PIN, AVR32_EBI_DATA_1_FUNCTION},
{ AVR32_EBI_DATA_2_PIN, AVR32_EBI_DATA_2_FUNCTION},
{ AVR32_EBI_DATA_3_PIN, AVR32_EBI_DATA_3_FUNCTION},
};
gpio_enable_module(EBI_GPIO_MAP, sizeof(EBI_GPIO_MAP) / sizeof(EBI_GPIO_MAP[0]));
AVR32_SDRAMC.mr=0; // normal mode
AVR32_SDRAMC.tr=0; // no refresh (T=0)
AVR32_SDRAMC.cr=
(AVR32_SDRAMC_CR_NC_11_COLUMN_BITS <<AVR32_SDRAMC_CR_NC_OFFSET)
|(AVR32_SDRAMC_CR_NR_13_ROW_BITS <<AVR32_SDRAMC_CR_NR_OFFSET)
|(AVR32_SDRAMC_CR_NB_TWO_BANKS <<AVR32_SDRAMC_CR_NB_OFFSET)
|(AVR32_SDRAMC_CAS_ONE_CYCLE <<AVR32_SDRAMC_CR_CAS_OFFSET)
|(AVR32_SDRAMC_DBW_16_BITS <<AVR32_SDRAMC_CR_DBW_OFFSET)
|(0 <<AVR32_SDRAMC_TWR_OFFSET)
|(0 <<AVR32_SDRAMC_TRC_OFFSET)
|(0 <<AVR32_SDRAMC_TRP_OFFSET)
|(0 <<AVR32_SDRAMC_TRCD_OFFSET)
|(0 <<AVR32_SDRAMC_TRAS_OFFSET)
|(0 <<AVR32_SDRAMC_TXSR_OFFSET);
AVR32_SDRAMC.hsr=AVR32_SDRAMC_HSR_DA_MASK;
AVR32_SDRAMC.mdr=AVR32_SDRAMC_MDR_MD_SDRAM;
// map SDRAM CS -> memory space
AVR32_HMATRIX.sfr[AVR32_EBI_HMATRIX_NR]|=1<<AVR32_EBI_SDRAM_CS;
AVR32_HMATRIX.sfr[AVR32_EBI_HMATRIX_NR];
U32 a;
for (a=0;a<VRAM_ls*VRAM_ys;a++) VRAM[a]=0;
for (a=0;a<VRAM_ls;a++) VRAM_empty[a]=0;
}
//------------------------------------------------------------------------------------------------
void VGA_screen()
{
U32 a,x,y,c,PA,t0;
wait_start(t0);
for (;;)
{
for (PA=_PAmo,a=0,y=0;y<VGA_ys;y++)
{
wait_start(t0);
if (y== 0) PA^=_PA_VGA_VS; else PA^=0; // VS on
if (y==VGA_VS) PA^=_PA_VGA_VS; else PA^=0; // VS off
PA^=_PA_VGA_HS; // HS on
port_PA->ovrc=PA^_PAmo;
port_PA->ovrs=PA;
wait_us(t0,VGA_t0);
PA^=_PA_VGA_HS; // HS off
port_PA->ovrc=PA^_PAmo;
port_PA->ovrs=PA;
wait_us(t0,VGA_t1);
*SDRAM=0; // blank (black)
if ((y>=VGA_y0)&&(y<VGA_y1))
for (x=0;x<VRAM_ls;x++)
{
c=VRAM[a];
*SDRAM=c>>4; // write pixel into SDRAM interface (address is ignored as I use only data bus pins)
a++;
*SDRAM=c; // write pixel into SDRAM interface (address is ignored as I use only data bus pins)
}
*SDRAM=0; // blank (black)
wait_us(t0,VGA_t2);
}
}
}
//------------------------------------------------------------------------------------------------
Main.cpp:
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
#include "System\include.h"
#include "pic_zilog_inside.h"
//#include "VGA_EBI_SMC.h"
#include "VGA_EBI_SDRAMC.h"
//#include "VGA_SSC.h"
//------------------------------------------------------------------------------------------------
void pic_copy(U8 *dst,U32 dst_xs,U32 dst_ys,U32 dst_bs,U8 *src,U32 src_xs,U32 src_ys,U32 src_bs)
{
U32 x0,y0,a0,l0;
U32 x1,y1,a1,l1;
U32 a; U8 c,m;
l0=1; l1=1;
if (dst_bs==1) l0=dst_xs>>3;
if (dst_bs==2) l0=dst_xs>>2;
if (dst_bs==4) l0=dst_xs>>1;
if (dst_bs==8) l0=dst_xs;
if (src_bs==1) l1=src_xs>>3;
if (src_bs==2) l1=src_xs>>2;
if (src_bs==4) l1=src_xs>>1;
if (src_bs==8) l1=src_xs;
for (a0=0;a0<dst_ys*l0;a0++) dst[a0]=0;
for (y0=0;y0<dst_ys;y0++)
{
y1=(y0*(src_ys-1))/(dst_ys-1);
a0=l0*y0;
a1=l1*y1;
for (x0=0;x0<dst_xs;x0++)
{
x1=(x0*(src_xs-1))/(dst_xs-1);
c=0;
if (src_bs==1)
{
c=src[a1+(x1>>3)];
c>>=7-(x1&7);
c&=1;
}
if (src_bs==4)
{
c=src[a1+(x1>>1)];
if (U32(x0&1)==0) c>>=4;
c&=15;
}
if (dst_bs==1)
{
c<<=7-(x0&7);
a=a0+(x0>>3);
dst[a]|=c; if (!c) dst[a]^=c;
}
if (dst_bs==4)
{
if (c) c=15;
if (U32(x0&1)==0) { c<<=4; m=0x0F; } else m=0xF0;
a=a0+(x0>>1);
dst[a]&=m;
dst[a]|=c;
}
}
}
}
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
int main(void)
{
VGA_init();
pic_copy
(
(U8*)VRAM,
VRAM_xs,
VRAM_ys,
VRAM_bs,
(U8*)pic_zilog_inside,
pic_zilog_inside_xs,
pic_zilog_inside_ys,
pic_zilog_inside_bs
);
VGA_screen();
}
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------------------
pic_zilog_inside.h:
const U32 pic_zilog_inside_xs=640;
const U32 pic_zilog_inside_ys=480;
const U32 pic_zilog_inside_bs=1;
const U32 pic_zilog_inside[]= // hard coded image
{
0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,
0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0x80000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,
0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000001,0x80000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,
...
0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000001,0x80000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,
0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000000,0x00000001,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,
0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,0xFFFFFFFF,
};
函数pic_copy只是将硬编码的图像复制到VRAM中.
The function pic_copy just copies hard-coded image into VRAM.
函数VGA_screen()在无穷循环中创建VGA信号，因此必须将其他任务编码为ISR或将其硬编码为暂停代码或在各个帧之间(但是，由于我的MCU时钟较小，这确实对我的设置提出了要求，没有足够的空间来做其他事情). VRAM被编码为16种颜色(每个像素4位)
The function VGA_screen() creates the VGA signal in endless loop so other tasks must be encoded into ISRs or hard coded into pause code or between individual frames (however this is really demanding on mine setup as I got small MCU clock so there is not much room for other stuff to do). The VRAM is encoded in 16 colors (4 bits per pixel)
8 4 2 1
Brightness B G R
亮度应该只用很少的电阻和二极管向R，G，B施加一些电压，但是较新的在HW侧实现，而我有这个电路(仅8种颜色):
The brightness should just adds some voltage to R,G,B with few resistors and diodes but newer implemented it on HW side instead I have this circuit (8 colors only):
二极管必须以相同的势垒电压快速充电，并且电容器必须为1nF.它可以避免由于使用的接口数据总线时序而引起的图像毛刺.另外，如果将来需要更多信息，请使用二极管来获得亮度，有关更多信息，请参见此处的R2R电流问题:
The diodes must be fast with the same barrier voltage and capacitors are 1nF. Its to avoid glitching of the image due to used interface data bus timing. Also the diodes are needed for the brightness if added in future for more info see the R2R current problem in here:
这篇关于STM32上的VGA像素分组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！