About DMA and user logic ,help!

Hello Yks,

I had to recently design a DMA LCD system. I used the HAL paradigm for the DMA, bascially using the template found in the software guide and a recursive ISR. I borrowed this code from a VGA application and changed a few things for the LCD system. Everything works fine!

Here are the code snippet highlights:

//open the dma channel

//Set Dma mode transfers

//Set DMA for streaming

// queue transfers

// queue the dma transfer to copy frame buffer

temp = alt_dma_txchan_send ( tx_chan,

(const void*)(main_frame_buffer),

(( PIX_MAP_WIDTH * PIX_MAP_HEIGHT ) + PIX_MAP_WIDTH) * 2 * 2,

(alt_txchan_done *)(vga_dma_done),

(void*)(&my_isr_context));

// Where my_isr_context is address of block where your image resides

void vga_dma_done(vga_dma_done_context *context) // VGA DMA ISR

{

// setup another dma to feed the frame buffer out the vga

alt_dma_txchan_send ( tx_chan,

(const void*)(context->frame_buffer_base),

((PIX_MAP_WIDTH * PIX_MAP_HEIGHT) + PIX_MAP_WIDTH) * 2 *2,

(alt_txchan_done *)(vga_dma_done),

(void*)(context));

}

// Above function is called recursively.

Two more notes: I used the streaming mode, this works well with the DMA.

Also, When you design your LCD logic make sure latency is zero.

Hope this helps a bit.

-Baycool