Propeller Prototyping Board doesn't want to power from USB
bgp
Posts: 34
I just brought two Propeller Prototyping Board units from Fry's (this: http://www.frys.com/product/6727005?site=sr:SEARCH:MAIN_RSLT_PG ) and tried to load a simple test SPIN program on it (using BST on my Mac). Only plugged in the USB power. (I have a DefCon 20 badge that has a similar setup on it's board so I figured this would work.) I get the "No Propeller Found" message.
On hunch, I check with a voltmeter between the 3.3v/VDD pinhole and ground and it gives me 0.93. I figure that's my problem. So plugged in via external power and flipped the switch for that and now it gives me 4.2v, and it's detected and I can load stuff on it.
Based on that, my specific questions are:
a) Is this thing supposed to be able to run from USB power only? Seems like it should (as I said I've seen it done before) - anything else I need to know or do to make that work?
b) Is it safe to run this thing at 4.2v? All the docs I've seen say 3.3v, so I'm not sure if what it's doing is safe or what.
On hunch, I check with a voltmeter between the 3.3v/VDD pinhole and ground and it gives me 0.93. I figure that's my problem. So plugged in via external power and flipped the switch for that and now it gives me 4.2v, and it's detected and I can load stuff on it.
Based on that, my specific questions are:
a) Is this thing supposed to be able to run from USB power only? Seems like it should (as I said I've seen it done before) - anything else I need to know or do to make that work?
b) Is it safe to run this thing at 4.2v? All the docs I've seen say 3.3v, so I'm not sure if what it's doing is safe or what.
Comments
No. Are you sure you measured between Vdd and Vss? What kind of external power did you use?
BTW, welcome to the forum!
-Phil
Got it on the external power.
Definitely measured from Vdd to Vss, just checked again - 4.19v. The plug specs say output: 6.3v, 0.4a. When I measure directly what comes from the end of the plug (putting the needles from the voltmeter on + and - on the plug) I get 8.4v. From where it says 5v on the board to Vss I get 6.6v. And when I measure from 3.3v/Vdd I get 4.2v.
I'm almost wondering if my voltmeter is messed up or something, since absolutely nothing seems to match the specs. But all of the measurements are repeatable with only slight variations (4.19v vs 4.20v etc.)
-Brad
http://forums.parallax.com/showthread.php/133182-Propeller-Protoboard-USB-Power-Hack
Here is my info on how to set Vbus to 500mA and how to override poweren# for use with USB charger
though I don't think proto board uses that, as no power switching is done.
http://forums.parallax.com/showthread.php/149550-USB-Power-your-Quickstart-board?p=1200054
The USB Proto Board has been discontinued (I think the serial variant still in production). Its replacement is the Project Board, which CAN be powered directly from USB and gives you more prototyping space. Check it here:
http://www.parallax.com/product/32810
If you have a need in the future, consider this one
Cheers!
@Daniel - gotcha, makes sense. I just picked up whatever they had on the shelf at Fry's since I was in a hurry but will definitely checkout the newer board next time.
If anyone has any other info on why it's running at a higher voltage, that'd be great. Otherwise, thanks.
(Ran it for about 10 hours last night power on, all seems well so far; assuming it's not an issue.)
-Phil