Avnet Employee (Regular Contributor)
Posts: 31
Registered: ‎09-18-2009

FRS K70 & LCD questions

Hello all,  I do have and SR initiated with Freescale, but any thoughts for my customer? I recieved the following 

On my K70 based Cash Handling unit we are basically almost to the point of production.  We have just received a small pre-production run of boards to build and field test.  The only hardware complaint I have received so far has to do with the LCD display.  Basically, I can’t clock the 800x480 display at a rate fast enough to avoid flicker.  Here are my display settings:


      LCDC_LPCR_TFT_MASK      |       //TFT Screen

      LCDC_LPCR_COLOR_MASK    |       //Color

      LCDC_LPCR_BPIX(0x7)     |       //bpp

      LCDC_LPCR_FLMPOL_MASK   |       //first line marker active low

      LCDC_LPCR_LPPOL_MASK    |       //line pulse active low

      LCDC_LPCR_END_SEL_MASK  |       //Use big-endian mode (0xFFAA5500 means R=AA,G=55,B=00)   

      LCDC_LPCR_SCLKIDLE_MASK |       //Enalbe LSCLK when vsync is idle

      LCDC_LPCR_SCLKSEL_MASK  |       //Always enable clock

      LCDC_LPCR_CLKPOL_MASK  |       //Active on positive edge of LSCLK. In TFT mode, active on negative edge of LSCLK.

      LCDC_LPCR_PCD(10);             //Divide 120 PLL clock by (10+1)=13 to get 10.9MHz clock

The display colors are bright and everything is fine but the display wants to ideally be clocked at 30MHz.  However I can’t do that or anywhere close to that.  From the above it can be seen I am only clocking it at 120MHz/11 = 10.9MHz.  When I divide the 120MHz clock down by 4 to reach 30Mhz I get “Under run Errors”.  The display looks torn and messed up.  So basically I lowered the clock rate (last line in the above settings) until it worked.  The problem is you can see flickering looking anywhere except right at it from the perfect angle.  It just doesn’t look that great because it is obvious I am pushing data at it too slow.

So, question…how can I increase the clock rate on my 800x480 and not cause under run errors?  Is this just a limitation of the K70 when using an 800x480 display?  I even took MQX and got rid of all my tasks except the GUI and it still does this so it seems like either there is some other setting wrong or there just isn’t the throughput to do this.


Avnet Employee (Regular Contributor)
Posts: 35
Registered: ‎12-01-2014

Re: FRS K70 & LCD questions

Hello Svallo,

Are you doing this testing using the Tower System?  If so, I have seen this exact same flicker, and it has to do with the Power Supply on the K70 Tower Card.  If you are using Tower, try to move the power to the Primary Elevator connector, it has higher output power regulator on it vs. the Processor card itself.