FFT Example - GlCD corrupts at XT - 8 X PLL enabled

[Bob Lawrence]

Example Recommended speed: "For example, if you are using 10MHz crystal, make sure you turn 8xPLL on, in that way the operating frequency will be 80MHz"

Problem: The FFT example runs fine at XT Xtal, 10Mhz - 4X PLL enabled but the Freqs are incorrect. With the 8X PLL enabled I get mostly garbage
on the GLCD.

Board Type: dsPIC Pro

Xtal : 10 Mhz

Glcd Init: Glcd_Init(&PORTD,8, &PORTD,9, &PORTD,10, &PORTD,3, &PORTG,12, &PORTD,11, &PORTB);

Compiler: mikroC, mikroElektronika C compiler
for Microchip dsPIC 30/33 and PIC 24 microcontrollers

Compiler Version: 3.0.0.0

Licensed: Yes

[LGR]

I've also noticed on the dsPIC PRO that the GLCD routines can't handle 80 mHZ. That sounds like a bug that needs to be fixed. In fact, I noticed that a couple of years ago when Pascal 1.0 came out.

[Bob Lawrence]

It's still broken. I 'm stuck until I can get some help.

[triplex]

Good morning,
I am using same board as you: dsPICPRO3
I tried the example and had the same problems in the beginning. There was no operation with the 8X PLL....after I reloaded the hexfile with 4X PLL it worked fine (only the displayed frequency-spectrum was doubled, as you said before).

Now the weird part: I just downloaded the examples again, tried it successful with 4X PLL, switched dsPICFLASH back to "XT w/PLL 8x - XT crystal osc. mode 8x PLL enabled" and it works like it is supposed to!
Maybe there is a new revision on the web...maybe you should try it!

Greetings


P.S.: The GLCD can handle 80MHz without any problems...OK, I havent tried 80mHz, my board doesnt support this ultra-slow-mode ;-) but with 80MHz it works great!

[LGR]

I suspect that the GLCD bug is dependent on the particular GLCD module; i.e. there are some delays in the library that become too short for certain models when you go to 80 mHZ. What SHOULD happen is that the library should compile the correct delay based on the PLL multiplier selected. I don't think that's happening reliably for some reason.

One more example of a bug that could be fixed if parts of the source were open.