HSPLL issue in a 16-channel RC servo driver

[be_jouster]

Hi all,

Currently I designing 16-channel rc servo driver. For now i just try for 2-channel only. As my hardware, I'm using 18F2331 and 10Mhz osc. I'm coded my firmware using ASM. I hook-up the output pin to the scope. The result as below:

1) 10Mhz osc with HSPLL enable - There is a signal on the scope but not as I programmed it to be. Sometimes my mcu like hang or something else.

2) 10Mhz osc without HSPLL - There is a signal on the scope as I programmed it to be. In term of time, it is 4 times bigger as my program target for 40Mhz operation.

Why could this happen? I really needs to run my firmware at 40Mhz to support 16 servos. Anyone know how to resolve this problem?

Thanks.

 

[potyo]

HSPLL issue

After enabling the PLL, you must power down the chip to ensure that PLL starts correctly, and after that check the signals.

 

[be_jouster]

Re: HSPLL issue

Thanks for reply.

After i tried your suggestion it still not working 10 Mhz with HSPLL enable. But when i tried 4Mhz with HSPLL enable, it is working (timming is bigger - but not an issue). So why it cannot work with 10 Mhz with HSPLL enable?

 

[be_jouster]

Re: HSPLL issue

By putting 0.1uf cap across power to ground resolve the problems .

Thanks anyway.