PI CHIP

[Mechanic]

.....and look at the waveform at the far left of the trace and see if there is jitter there......

This should have read:

and look at the waveform at the far RIGHT of the trace and see if there is jitter there.....



Paul, are you sending all of your data to the lcd in one go? If you are, try sending 1 byte/ tx cycle.

Cheers Mick

[6666]

10 mhz I have thanks
I see jaycars have 8 mhz

[moodz]

This should have read:

and look at the waveform at the far RIGHT of the trace and see if there is jitter there.....



Paul, are you sending all of your data to the lcd in one go? If you are, try sending 1 byte/ tx cycle.

Cheers Mick

Hi Mick ... I think the jitter issue was related to my use of the internal RC clock ... it runs at 7.37 mhz and probably isnt that clean to start with then the PLL multiplies it by 16 which would amplify any jitter issues. The code is built around the TX pulse .... The TX pulse itself is generated by a dedicated PWM generator inside the chip that is driven directly by the clock and code wont affect it unless you access a config register. My code should not be touching this after initialisation. At the start of each TX pulse an interrupt is generated. DSPICs are supposed to guarantee a hard / fixed 4 cycle latency for interrupts and the first thing the interrupt does is fire the sample pulse timer that will trigger the sample pulses at preconfigured times after TX cycle start. Again the code does not need to touch the sample pulse on / off times as these too are "hardwired".
I have run a Tx pulse and two sample pulses with spacings of 25 ns and not a single glitch over 2 hours ( 10 Mhz crystal fitted ). This sucker can generated a 50 ns wide sample pulse if such a thing could be used ??!!

The down side of using the overclock crystal at 10 Mhz is that the chip sucks alot more power now from the 5 volt supply because everything is spinning over much faster inside.

The LCD loop runs in the background main loop ..... however it does make use of a low priority interrupt for a timer ( strobing the LCD control lines etc ) ....it is just possible that there is clash with the top priority TX interrupt and that is somehow violating the "guaranteed" 4 cycle interrupt latency ... that would cause an issue. I could remedy by replacing the timer interrupt with a looping counter subroutine ...

Paul.

[moodz]

clarification

... My code should not be touching the tx and sampling timing hardware except at initialisation and if you change it on the menu.

moodz.

[moodz]

10 mhz I have thanks
I see jaycars have 8 mhz

8 mhz would work however I would have to change the timing constants in the code. A bit more effort and I could add it to the LCD menu

Use 10 Mhz for now ...

moodz

[mickstv]

Hi Paul, i've just installed the crystal and caps software loaded ok and I'm happy to say it all looks good no more jitter. The only think I did notice which isn't really a problem is when you turn the rotary encoder fast it seems to some times stop or reverse in number change but at a slower pace it's fine. Also notice the inclusion of the Damping menu.

EDIT : Just noticed if you try to change any settings in TXF Per once you select either X1, X10, or X100 the LCD blanks out.



Mick

[moodz]

Hi Paul, i've just installed the crystal and caps software loaded ok and I'm happy to say it all looks good no more jitter. The only think I did notice which isn't really a problem is when you turn the rotary encoder fast it seems to some times stop or reverse in number change but at a slower pace it's fine. Also notice the inclusion of the Damping menu.

EDIT : Just noticed if you try to change any settings in TXF Per once you select either X1, X10, or X100 the LCD blanks out.



Mick

errr dont change that setting for now ... there is a bug I noticed where there is no safety net for the frequency value ... it goes to zero when you change it and the interrupts arrive too fast crashing the chip. I will look into it but having too much fun with my blocking FETs at the moment.

Paul

[moodz]

errr dont change that setting for now ... there is a bug I noticed where there is no safety net for the frequency value ... it goes to zero when you change it and the interrupts arrive too fast crashing the chip. I will look into it but having too much fun with my blocking FETs at the moment.

Paul

I will look into the timing on the rotary encoder also.

[mickstv]

I will look into the timing on the rotary encoder also.

This one isn't really an issue the control does still work.

Hows the blocking fet electronics going ?




Mick

[Carl-NC]

The only think I did notice which isn't really a problem is when you turn the rotary encoder fast it seems to some times stop or reverse in number change but at a slower pace it's fine.

You're turning it faster than the software can keep up.

[moscadondres]

?

[mickstv]

Hi moodz,
How do you connect the 10Mhz crystal to the 30F4012,thank you for reply.

Hi moscadondres, Paul wrote how to a few posts ago, but any way this is what I did...

1 Remove satlock button from pin 10 and remove the 10k resistor from pin 10 of the micro.
2 Fit 10Mhz crystal between pin 9 and 10.
3 Get two 22pf ceramic capacitors and solder one end of each capacitor to pin 9 and pin 10, then the other side of the capacitors solder to ground.



Mick

[moodz]

[quote=mickstv;135594]This one isn't really an issue the control does still work.

Hows the blocking fet electronics going ?

Mick[/quote


see http://www.geotech1.com/forums/showp...7&postcount=31

update in Model T circuit thread.



This was the main "blocker" to getting the rest of the signal chain going.

Paul.

[mickstv]

[quote=moodz;135609]

This one isn't really an issue the control does still work.

Hows the blocking fet electronics going ?

Mick[/quote


see http://www.geotech1.com/forums/showp...7&postcount=31

update in Model T circuit thread.



This was the main "blocker" to getting the rest of the signal chain going.

Paul.

Thanks i'll go and have a look see.


Mick

[moscadondres]

Thank you micktv,thank you moodz for your work.