PIC overclock

[Gallymimu]

Would you show the truths so the trust can be properly granted?

-ichan

No, thanks.  There's a lot of config and optimizations that must be made to max out the I/O execution speed on the PIC32 (peripheral clock, wait states, execute from ram, etc.) if I'd want to give it a fair shake. Not really interested in doing that.  But by all means don't let me stop you from showing the differences since you probably know this stuff far better than I.

[Ichan]

...since you probably know this stuff far better than I.

No, I don't. I have no experience with pic32 yet, had some with dspic. My coming plan will need quite heavy math involving 64bit integer, also will need some output to generate pulse stream in mhz range. Weighing out the mcu now - one interesting fact about pic32 is it is one of a few 32bit mcu in the market with compact package, even in dip.

ARM mcu known to have relatively slow i/o, how about MIPS?

-ichan

[Gallymimu]

No, I don't. I have no experience with pic32 yet, had some with dspic. My coming plan will need quite heavy math involving 64bit integer, also will need some output to generate pulse stream in mhz range. Weighing out the mcu now - one interesting fact about pic32 is it is one of a few 32bit mcu in the market with compact package, even in dip.

ARM mcu known to have relatively slow i/o, how about MIPS?

-ichan

In trying to find some examples for the PIC32 I/O vs dsPIC I did come across a lot of complaints about ARM.  I saw people having problems with the PIC32 but did see a few references to getting it up in the 10s of MHz with proper configuration.

do you really need to toggle I/O fast under software control or can you use the PWM modules?

[Ichan]

The subject is pulse counts over time, so i think pwm module can not be used - imagining it to be driven by a timer tick for now.

There will be 6 pulse stream output, none will be over 10 mhz.

Where do you found the 10s mhz output sample?

-ichan

[Gallymimu]

The subject is pulse counts over time, so i think pwm module can not be used - imagining it to be driven by a timer tick for now.

There will be 6 pulse stream output, none will be over 10 mhz.

Where do you found the 10s mhz output sample?

-ichan

Here is the best one I found:

http://blog.flyingpic24.com/2009/03/18/testing-the-pic32-io-speed/

I don't think it will be fast enough if you need to have 6 pulse streams.

Did you consider using a FPGA or CPLD just for the pulse streams and do the math in the microprocessor?

I had a similar problem where I wanted to use PWM for high frequency short pulse width but I need to have an exact count.  I couldn't find a way to do it without using a timer instead.

Maybe you can use PWM and a counter input to count pulses.  Then the counter can have an interrupt that turns off the PWM. 

[Ichan]

Thanks for the link, i found also on microchip forum that there will no problem with i/o speed.

Any info about footprint compatibility between pic32 and dspic33? I mean, what pic32 and dspic33 which is compatible to each other? I gonna put them on my shopping list.

-ichan

[Skarden]

Hello,
just to open again this post, I made some tests with the PIC32MX150F128 and the PIC32MX250F128.
I confirm that, increasing the internal core voltage, It's possible to acheive a stable configuration at 80MHz (x20 Multiplier).
At 88MHz (x21 multiplier) the PLL seems to be in trouble as the output frequency is not stable but the core still works without crashes.

To do that I simply used a diode 1N4148 connected between the +3.3V (VDD) and the Vcap (Pin 20);
this supply the core at around 2.6V. As solutions said in a previous reply, the internal regulator don't see what we are doing externally so it come back at work as soon as the external voltage is removed.

I know, it's for the fun, but it can run at exactly the double of the original speed (40MHz).

I made several tests, and all the projects I did never crashed.

I adapted the De Jasio project in order to generate a VGA video output with a lot of graphic tests using math functions and it never crashed.

I tried also to heat the PIC with an hot air solder reaching a very high temperature without any crashes

[sergey]

I once successfully overclocked a PIC16F88 (so this should be valid for similar 5V-based PICs) for use in a video character generator (OSD) to 32 MHz using a 5V TTL oscillator (XO) and recently did the same during my Bachelor thesis - an Infineon XC16x MCU was overclocked from 40 Mhz to ~60 MHz by it's PLL.

The most limiting factor in overclocking any small MCU is RAM and Flash speed - heat is never an issue with small MCUs
(if it doesn't get warm in operation, it won't get hot while overclocking - don't worry...).

But generally, overclocking MCUs is of no use, except if the application is so special like video, that you need every MIPS.
If you're overclocking because code runs slow, first try to fix your code. And never use overclocked MCUs in industrial designs