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18F14K50 at 5 volts

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futz

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I'm tinkering with an 18F14K50, which is rated for 1.8V to 5.5V. Once I updated MPLAB to the latest, the PICkit2 happily connects to it and supplies 3.3V to it.

For reasons related to my circuit I want to supply it with 5V. When I do this and try to have MPLAB connect I get this error:

Code:
Found PICkit 2 - Operating System Version 2.32.0
PK2Error0023:  Target Vdd measured at   4.99V which is outside the programmable range of this device (  1.88V -   3.60V)
PICkit 2 Ready

Is this just because MPLAB support for these chips is still in beta?

The PICkit 2 program, v2.61, seems to be ok with external 5V supply, but refuses to allow the PICkit 2 to supply more than 3.3V.
 
Its a tricky part because the PGD and PGC pins are multiplexed with the D+ and D-, which I think only support 3.3V. I only used the Pickit 2 as a standalone. If you got this for the USB, then you could power the device from USB, or a separate battery supply, at least that's what I did.
 

futz

Active Member
Its a tricky part because the PGD and PGC pins are multiplexed with the D+ and D-, which I think only support 3.3V. I only used the Pickit 2 as a standalone. If you got this for the USB, then you could power the device from USB, or a separate battery supply, at least that's what I did.
Ah, I see. You can run it at 5V, but you can't program it at 5V. That makes more sense then. So essentially, tho it can run at 5V, in practice I may as well consider it to be a 3.3V chip. I can live with that. I'm pretty used to level-shifting things now, what with the LPC2148 stuff I've done lately.

I didn't get it for the USB, tho I may yet play with that. I was just starting a new project and had a couple 18F14K50's so I thought I'd use one.

Anyway, the 3.3V thing isn't a big deal. For now I just let the PICkit 2 supply the MCU power and power the breadboard with 5V.
 
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Anyway, the 3.3V thing isn't a big deal. For now I just let the PICkit 2 supply the MCU power and power the breadboard with 5V.
I would still run the chip off the breadboard power, but maybe that isn't convienant? The 18f14k50 has its own internal 3.3V regulator for the USB stuff.

If you happen to be using the Pickit2 low pin count demo board, just make a little pigtail to run over from the breadboard power, the pads are already there. Level conversion makes a real birds nest of wires.
 

futz

Active Member
I would still run the chip off the breadboard power, but maybe that isn't convenient? The 18f14k50 has its own internal 3.3V regulator for the USB stuff.
The chip is on the breadboard, so it would be convenient. But when I supply it with 5V, MPLAB refuses to connect. I could put a 3.3V regulator on the breadboard, but like I say, for now it's just as easy to have the PICkit 2 supply it.

EDIT: After thinking about it for a bit, I realized what you probably meant. Run it at 5V breadboard power to avoid level shifting. Switch the power off to program and back on to run.

Trouble with that is that I hate flipping switches to program (though I've done it a lot - Motorola 68HC programmer), and I'd have no debugging available that way. May end up doing it anyway...

If you happen to be using the Pickit2 low pin count demo board, just make a little pigtail to run over from the breadboard power, the pads are already there.
Nope. I don't own one. Probably never will.

Level conversion makes a real birds nest of wires.
Yes, sometimes it gets kinda messy.
 
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AtomSoft

Well-Known Member
Futz I have happily powered a LCD with5v and mcu with 3.3v.as long as mcu is 5v tolerant meaning why not just power mcu with lower voltage and other devices with higher voltage?
 
EDIT: After thinking about it for a bit, I realized what you probably meant. Run it at 5V breadboard power to avoid level shifting. Switch the power off to program and back on to run.

Trouble with that is that I hate flipping switches to program (though I've done it a lot - Motorola 68HC programmer), and I'd have no debugging available that way. May end up doing it anyway...
Yes that's what I meant. But that doesn't keep you from the switch, as I found out on re-trying this part.

For some reason I thought I could leave the 5V to the device and program the the device at 3.3V, Wrong!:eek: Rechecked, and had to disconnect the USB power for programming, brain burp again......arghhh.
 

futz

Active Member
Futz I have happily powered a LCD with5v and mcu with 3.3v.as long as mcu is 5v tolerant meaning why not just power mcu with lower voltage and other devices with higher voltage?
Hey Jason. I was already doing that, as I already mentioned. :p

Work is so nuts that I only get an hour with it per night. Tonight I wired up a LM386 and a speaker to it and started making some crazy noises. I may add a DAC or two to it to make life simpler.

I'm toying with the idea of making a simple synth. Maybe even a not-so-simple synth. :) I'll have to add MIDI input to it (very simple) so I can play it from one of my keyboards. But for now I'm just tinkering with the basics.
 
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