I am currently trying to get a BeagleBoneBlack to comply with Class B Radiated Emissions levels.
I am seeing noise spikes at various harmonics which I believe are originating from the LCD PCLK running at approx. 38MHz.
These are spikes are at 307, 345, 384, 422, 460, 499, 537MHz, etc. and are at or above the limit for Class B emissions.
Has anyone else managed to solve this problem and limit the harmonics propagating through the system?
Thanks.
Not sure if this is what you need, but I dont remember having issues with the LCD, however the 12MHz clock (and its harmonics) feeding the HDMI was quite troublesome.
If you dont need hdmi, you can disable CLKOUT1 (XDMA_EVENT_INTR0) by default by setting SYSBOOT[5] low. If you do need it, then you may need to think of a better way of feeding the hdmi clock.
HTH,
Gaurav