[DE1] Making the VGA works with the IP VGA Controller

Hi all!

I'm new in DE1 KIT.

I'm building a SoC that displaying data from SDRAM into he screen through VGA.

My SoC contents:

- Nios II

- On-Chip Memory

-JTAG-UART

- System ID

- SDRAM

- VGA

I want to display data from SDRAM to VGA by using DMA for reading data from SDRAM to VGA. My C program write data to SDRAM by NIOS. Then I use DMA to read data from SDRAM to VGA. When the interrupt occur, DMA will read 640 value (1 line) from SDRAM to VGA.

My VGA core has a FIFO to buffer data. When fifo is empty, the VGA core will make a interrupt signal to control the transferring of DMA.

My system has some problems such as:

- First: When I use NIOS II to verify the read, write of SDRAM, it operates unstablely. I use "for" loop to write and read data to SDRAM but it just correct in the first 154 values

- Second: When the interrupt occur, DMA only operates within two loop, in third loop, DMA reports the error : "Can post request..."

Anybody can help me. please!

Thanks so much!