we are using the LCDC to transfer data to another device. our device produces video frames at varying rates from almost 0 to 100 Hz depending on customer input. I want the video frames to come out at whatever rate they are produced by the customer. to do this I am enabling and disabling the RASTER_EN in the RASTER_CTRL register. I enable the DONE_EN interrupt to detect when the transfer is complete. it takes about 10 ms to transfer our video frame.
but...for some reason I am getting 3 DONE interrupts for every time I send a frame. here is the basic sequence:
clear DONE in LCD_STAT
enable DONE_EN in RASTER_CTRL
enable RASTER_EN in RASTER_CTRL
<a couple of housekeeping statements>
disable RASTER_EN in RASTER_CTRL (the controller will finish the frame after starting)
...
HW interrupt #1
TSCL says it has been 5 us since the transfer started
LCD_STAT==0x00000001
RASTER_CTRL==0x00000088
acknowledge interrupt and return
...
HW interrupt #2
TSCL says it has been 1-2 us since the last HW interrupt
LCD_STAT==0x00000001
RASTER_CTRL==0x00000089
acknowledge interrupt and return
...
HW interrupt #3
TSCL says it has been 10 ms since the last HW interrupt
LCD_STAT==0x00000141
RASTER_CTRL==0x00000088
acknowledge interrupt and return
...
repeat until tired
after extensive text searching I believe there is only one place where I set the DONE_EN bit in RASTER_CTRL, yet it is always on when I get an interrupt. I tried setting a watchpoint but it never breaks despite the fact I am writing RASTER_CTRL all the time
also, the RASTER_EN bit is NOT on when I receive the first HW interrupt, but it IS on when I receive the second HW interrupt - how can that be?
in my current setup video is going out at 50 Hz. is there a problem using the LCDC is this way? or am I missing something here?
