Hi,
I designed and built the LED system shown in the link.
http://www.autoartisans.com/rings/Barge1a.jpg
I'm finally trying to track down a problem we ran into back in 2009/2010. When we change the GRPPWM register from a larger value to a smaller value to dim the 12 channels we have connected to RGB and White LEDs. The scenario is as follows. We'll set the PWM registers to create a specific colour. Then we may want to slowly dim this colour to dark using the GRPPWM register. We do this by periodically sending out a smaller GRPPWM value to dim the overall intensity. Each time we send out an IIC message with 18 bytes. The Control/Address(0x82), 16 PWM channels and the GRPPWM value.
If, every 40mS, I send out a new GRPPWM value that is smaller by 4, it works most of the time but there are occasional errratic flashes where the RGB channels are suddenly quite bright as it happens at the lower PWM value. We're certain our IIC communications is functioning since we don't have any trouble changing any of the regular PWM registers. If we did the flashes would be coloured differently.
Needless to say the flashing is disconcerting and we've had clients comment negatively about it so I've been asked to see if we can fix it.
Thanks
John