Composite Video Generating

I got it working on my r2r ladder without an op-amp now (I mean the signal b/w not color yet). I only needed to change the pin numbers.

Can someone tell me how to add dma?

I've just found some resistors for an R-2R ladder but they are only 1% tolerance. I was going to measure them more accurately and select some for the ladder, otherwise things start going wrong after 5 bits. Even then I think there will be too much noise on the digital outputs for full 8 bit accuracy. I'll see how well I can do.

DMA for the external memory port is quite hard to set up as it is AHB DMA - I use it in the VGA library but the code is impossible to follow :grin: I'll try and do a simpler example once I've got the ladder done.

stimmer:
I've just found some resistors for an R-2R ladder but they are only 1% tolerance. I was going to measure them more accurately and select some for the ladder, otherwise things start going wrong after 5 bits. Even then I think there will be too much noise on the digital outputs for full 8 bit accuracy. I'll see how well I can do.

DMA for the external memory port is quite hard to set up as it is AHB DMA - I use it in the VGA library but the code is impossible to follow :grin: I'll try and do a simpler example once I've got the ladder done.

I have 8 bit now. With 5% tolerance. (R is 10K each. I use 2 of them for the 2R. I know that this resistor is a bit too high)

Hmm, too bad. Isn't dma just setting a source and a destination pointer? On the ds for example there are functions like these:

void MI_DmaCopy32(u32 dmaNo, const void *src, void *dest, u32 size);

Which you use like this:

MI_DmaCopy32(3, &px[0], VramPixels,512 * 192);

Aren't there such functions on the due?

Here is an example of a picture generated with the due. (It is captured in jpeg using the camera I use for viewing it, so not the best quality)

DSC00137.JPG

With 5% resistors the R-2R ladder may lose too much accuracy. 5% of 255 is almost 13 which is a 4-bit number, so you could lose 4 bits of accuracy out of the 8, which is too much. Try connecting the analog output of the ladder to an analog input on the Due, then write a sketch which outputs 0-255 onto the ladder and reads the value on the analog input. You might find that the ladder isn't monotonic (sometimes when the input goes up by 1 the output voltage goes down instead of up).

THe DMA needs to be continuous (a bit like an audio buffer would be, just a lot faster) which is why it's more complicated than just DMAing blocks of memory.

stimmer:
With 5% resistors the R-2R ladder may lose too much accuracy. 5% of 255 is almost 13 which is a 4-bit number, so you could lose 4 bits of accuracy out of the 8, which is too much. Try connecting the analog output of the ladder to an analog input on the Due, then write a sketch which outputs 0-255 onto the ladder and reads the value on the analog input. You might find that the ladder isn't monotonic (sometimes when the input goes up by 1 the output voltage goes down instead of up).

THe DMA needs to be continuous (a bit like an audio buffer would be, just a lot faster) which is why it's more complicated than just DMAing blocks of memory.

Yea, but it works good enough for now. I will use other resistors (1%) later on.

Oh, okay. I realize how it need to work now. I will try to understand your code, since I only need to change the frequency and the source pointer.

Here's the sketch I used to check my ladder:

char pins[]={34,35,36,37,38,39,40,41};

void writeval(int v){
  for(int i=0;i<sizeof(pins);i++){
    digitalWrite(pins[i],v&1);
    v>>=1;
  }
}

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  for(int i=0;i<sizeof(pins);i++)
    pinMode(pins[i],OUTPUT);
}

void loop() {
  int l=0;
  for(int i=0;i<(1<<(sizeof(pins)));i++){
    writeval(i);
    delay(10);
    int m=analogRead(0);
    printf("%d : %d  d=%d\n",i,m,m-l);
    if(m<l)printf("!!!!!!ERROR!!!!!!!!!! non-monotonic\n");
    l=m;
  }
  delay(2000);
}

If you get errors then just swap the resistors around until they go away.

I've tried some things with dma, but now my arduino doesn't work anymore. I have seriously no idea what's the problem.

Edit: It works again. I pressed the erease and the reset button at the same time, and were able to upload a sketch again. After that everything worked well again.

Gericom:
I've tried some things with dma, but now my arduino doesn't work anymore. I have seriously no idea what's the problem.

Edit: It works again. I pressed the erease and the reset button at the same time, and were able to upload a sketch again. After that everything worked well again.

Lucky men, I know this kind of happiness...

Markus_L811:

Gericom:
I've tried some things with dma, but now my arduino doesn't work anymore. I have seriously no idea what's the problem.

Edit: It works again. I pressed the erease and the reset button at the same time, and were able to upload a sketch again. After that everything worked well again.

Lucky men, I know this kind of happiness...

Yea, first I thought it has broken. But then I just tried some random things, and then by purpose the bossac com port connected to my pc.

By the way, I changed the loop (with asm code) and now it is 330 px width.

Success! 8) :grin: XD

stimmer:
Success! 8) :grin: XD

:astonished: Cool! May I have your code?

The code needs tidying and commenting and debugging before I can share it (and before I forget how it works). I have got colour out of 3 monitors so far so it is looking good. This is using NTSC timings, I will try PAL another day. Resolution is 640x200 (or about 700x220 with overscan), but practically the Arduino won't be fast enough or have the ram to make use of all that. I may aim for a 160x200 mode.

Grayscale, colour bars and dot crawl :slight_smile:

stimmer:
The code needs tidying and commenting and debugging before I can share it (and before I forget how it works). I have got colour out of 3 monitors so far so it is looking good. This is using NTSC timings, I will try PAL another day. Resolution is 640x200 (or about 700x220 with overscan), but practically the Arduino won't be fast enough or have the ram to make use of all that. I may aim for a 160x200 mode.

Grayscale, colour bars and dot crawl :slight_smile:

Sorry, but I wanted to make such library. I really appreciate your help, but I want to do things myself. Could you give me the dma stuff at least?

This is just the DMA section of the code:

// Continuous DMA -> SMC port (pins 34-41)
// by stimmer

// set up 2 DMA buffers and a linked list
// 888 and 222 is NTSC timings (~15750 buffers/sec)
uint8_t dmabuf[2][888];
uint32_t dmall[10]={(uint32_t)dmabuf[0],0x60000000,0x22060000+222,0x20000000,(uint32_t)(dmall+5),
                    (uint32_t)dmabuf[1],0x60000000,0x22060000+222,0x20000000,(uint32_t)dmall};
int cbuf=0; // current buffer index

void  DMAC_Handler()
{ 
    uint32_t dummy=REG_DMAC_EBCISR; // clear DMA interrupt flag
    dmall[2+5*cbuf]=0x22060000+222; // may not be needed

  // write to dmabuf[cbuf] here   
  // you only have 6 clock cycles per byte!  
  // write words and longs where you can for speed
  
    cbuf=1-cbuf;
}

void setup() {
  
  // set up memory controller
  REG_PMC_PCER0= 1<<9; 
  REG_SMC_SETUP0=0;  
  REG_PIOC_PDR=0b1111111100;
  REG_PIOC_ABSR&=~0b1111111100;  
  REG_SMC_WPCR=0x534d4300;
  REG_SMC_SETUP0=0x00000000;
  REG_SMC_PULSE0=0X00000101;
  REG_SMC_CYCLE0=0X00000006; // this sets the DMA rate -  84/6=14 MByte/sec
  REG_SMC_TIMINGS0=0;
  REG_SMC_MODE0=0x00000000;
  
  // this code puts DMA priority above CPU.
  MATRIX->MATRIX_WPMR=0x4d415400;
  for(int i=0;i<6;i++)MATRIX->MATRIX_MCFG[i]=1;
  MATRIX->MATRIX_MCFG[4]=4;
  for(int i=0;i<8;i++)MATRIX->MATRIX_SCFG[i]=0x01000008;
  MATRIX->MATRIX_SCFG[6]=0x011200ff;
  MATRIX->MATRIX_PRAS0=MATRIX->MATRIX_PRAS1=MATRIX->MATRIX_PRAS2=0x00000000;
  MATRIX->MATRIX_PRAS3=MATRIX->MATRIX_PRAS4=MATRIX->MATRIX_PRAS5=0x00000000;
  MATRIX->MATRIX_PRAS6=0x00030000;
  MATRIX->MATRIX_PRAS7=MATRIX->MATRIX_PRAS8=0x00000000;

  // set up DMA
  REG_PMC_PCER1= 1<<7;  
  REG_DMAC_WPMR=DMAC_WPMR_WPKEY(0x444d4143);
  REG_DMAC_EN=1;
  REG_DMAC_GCFG=0x00;
  REG_DMAC_CFG5=0x10702200;
  REG_DMAC_DSCR5=(uint32_t)dmall;
  REG_DMAC_EBCIER=1<<5;
  NVIC_EnableIRQ(DMAC_IRQn);
  
  // start DMA
  REG_DMAC_CHER=1<<5;

}

void loop() {
  
}

stimmer:
This is just the DMA section of the code:

// Continuous DMA -> SMC port (pins 34-41)

// by stimmer

// set up 2 DMA buffers and a linked list
// 888 and 222 is NTSC timings (~15750 buffers/sec)
uint8_t dmabuf[2][888];
uint32_t dmall[10]={(uint32_t)dmabuf[0],0x60000000,0x22060000+222,0x20000000,(uint32_t)(dmall+5),
                   (uint32_t)dmabuf[1],0x60000000,0x22060000+222,0x20000000,(uint32_t)dmall};
int cbuf=0; // current buffer index

void  DMAC_Handler()
{
   uint32_t dummy=REG_DMAC_EBCISR; // clear DMA interrupt flag
   dmall[2+5*cbuf]=0x22060000+222; // may not be needed

// write to dmabuf[cbuf] here  
 // you only have 6 clock cycles per byte!  
 // write words and longs where you can for speed
 
   cbuf=1-cbuf;
}

void setup() {
 
 // set up memory controller
 REG_PMC_PCER0= 1<<9;
 REG_SMC_SETUP0=0;  
 REG_PIOC_PDR=0b1111111100;
 REG_PIOC_ABSR&=~0b1111111100;  
 REG_SMC_WPCR=0x534d4300;
 REG_SMC_SETUP0=0x00000000;
 REG_SMC_PULSE0=0X00000101;
 REG_SMC_CYCLE0=0X00000006; // this sets the DMA rate -  84/6=14 MByte/sec
 REG_SMC_TIMINGS0=0;
 REG_SMC_MODE0=0x00000000;
 
 // this code puts DMA priority above CPU.
 MATRIX->MATRIX_WPMR=0x4d415400;
 for(int i=0;i<6;i++)MATRIX->MATRIX_MCFG[i]=1;
 MATRIX->MATRIX_MCFG[4]=4;
 for(int i=0;i<8;i++)MATRIX->MATRIX_SCFG[i]=0x01000008;
 MATRIX->MATRIX_SCFG[6]=0x011200ff;
 MATRIX->MATRIX_PRAS0=MATRIX->MATRIX_PRAS1=MATRIX->MATRIX_PRAS2=0x00000000;
 MATRIX->MATRIX_PRAS3=MATRIX->MATRIX_PRAS4=MATRIX->MATRIX_PRAS5=0x00000000;
 MATRIX->MATRIX_PRAS6=0x00030000;
 MATRIX->MATRIX_PRAS7=MATRIX->MATRIX_PRAS8=0x00000000;

// set up DMA
 REG_PMC_PCER1= 1<<7;  
 REG_DMAC_WPMR=DMAC_WPMR_WPKEY(0x444d4143);
 REG_DMAC_EN=1;
 REG_DMAC_GCFG=0x00;
 REG_DMAC_CFG5=0x10702200;
 REG_DMAC_DSCR5=(uint32_t)dmall;
 REG_DMAC_EBCIER=1<<5;
 NVIC_EnableIRQ(DMAC_IRQn);
 
 // start DMA
 REG_DMAC_CHER=1<<5;

}

void loop() {
 
}

Thanks, but what if I want to transfer only one buffer at a time? (After calling REG_DMAC_CHER=1<<5;)

The last few days, I worked on writing a wss. It was not easy, but now widescreen is possible. I have also made some progress on the color stuff. But not on the arduino yet. I first made an application on the pc to generate composite video signals from pictures. It works great. (I got another tool to get it colored again) I will work soon on color for the arduino.

DSC00342.JPG

Some progress on coloring is made, but I can't get those colors to be smooth.
On the picture you can see from top to bottom Red, Green and Blue. (The green is the most bad one. But you can see some green spots)

DSC00393.JPG

This is much better already. (Same picture as above):

DSC00396.JPG

Light blue (#00c0c0):

DSC00444.JPG