about VGA display

[Altera_Forum]

Now,I am puzzled at VGA display,I look trough signaltap,and I am sure the vs,hs are right,and RGB signals show up in active period(maybe the RGB is not the correct image data,but the RGB is not all zero),I think there should be some thing to display,but the VGA is black. 

I post the signaltap cutshot in attarchment.    thanks for your help!

[Altera_Forum]

i don't see an attachment 

 you mention data, vs, hs. how about data enable or similar?

[Altera_Forum]

thanks for your reply~ 

 Now,I am using DE2 board , when I configure A/D chip(ADV7181) using the files (I2C_Controller.v,I2C_AV_Config.v),ADV7181 always back "ACK" high level,that means FPGA cannot comminicate with ADV7181,and I am sure ADV7181 is OK. so, I write a simple I2C confiuration programme ,ADV7181 back "ACK" low level,that says I2C confiruration success,but I donnot understand why using the demo I2C configuration programme is always unsuccessful??