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Problem with PIC16F877A on JuneBug

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Shipton

New Member
VPP-VPP
5V->VDD (both)
GND->VSS (both)
PGD->data
PGC->clock

I opened up PIcKit2, selected a PIC16F877A as my device, and it reads it. I clicked Verify, and it did verify, but told me there was a VDD voltage level error. "Check target and retry operation." But then when I click verify again, it does it, successfully, but stills gives me that error message. What does that mean?

I seem to keep having trouble with PicKit acting screwy. Not toally sure why. For instance right now I have it going to the PIC16 which is empty, and I'm not doing anything, but the clock light is going. And if I read the PIC16, it comes up empty, which is right. But if I do a blank check, it claims it fails at 0x0.

And in MPLab, I get this gem:
Initializing PICkit 2 version 0.0.3.63
Found PICkit 2 - Operating System Version 2.32.0
PICkit 2 Unit ID = OlHoss
Target power not detected - Powering from PICkit 2 ( 5.00V)
PK2Error0024: PICkit 2 was unable to establish a valid Vdd on the target (Attempted 5.00V - Read 2.16V)
PICkit 2 Ready

(PicKit indicates Vdd is stable at 5V). I did a multimeter check at this point across Vdd and Vss on the uC, and got around 0.17V or something. So I unplugged it and plugged it back in, and got around 3.34V. After trying the above (and getting the same problems), it again complains that Vdd is 2.12V. Is it just that the USB is unable to provide enough power?
 

blueroomelectronics

Well-Known Member
It usually means the target is loading the Junebugs 100mA supply. One solution is jumper U5V & +5V on the top 16 pin header. This will bypass the BS250 MOSFET switch.
 

Shipton

New Member
Went the easy route first and jumped U5V and +5V. Worked like a charm

While you're here, quick question regarding the attachment of 3.3V uCs to the ICD - all the white arrows in the diagram that go to "3.3V," what does that mean?
 
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