I've been doing some current measurement tests on my own, using the customary prime number calculation program (click on the link
to refer to it). Of course something similar was done here
, and if you want a full comparison, then you should refer to the post: http://forums.parallax.com/discussion/170380/new-p2-silicon/p1
. However, nevertheless, I thought it would be useful to do some tests of my own, and share my findings.
Basically, I measure the USB current as consumed by the boards, for both Rev. A and Rev B. The tests are run using "primes.c" loaded via FlexGUI. The program executes at 160MHz by default. For both boards, I measured the current from attachment to detachment of the USB cable. The program execution procedure consists on finding prime numbers between 1 to 100000, and then between 1000000000 to 1000100000, while measuring the current on the go. The results that the program outputs are not within the scope of this analysis.
So, attached are the results that I've got with my RevA and RevB boards. There is also a zip file containing the raw data. In both graphs, you can see that the current dips while the program calculates prime numbers (first between 1 to 100000, and then between 1000000000 to 1000100000). I find this odd, because the P2 is actually consuming more power while waiting for user input than when doing the actual calculations. Perhaps the explanation is that the program is also busy outputting results to serial when performing calculations, hence the drop in power consumption, but I have to confirm this with both boards.
However, it is confirmed that the new revision consumes roughly half the power, and even less when the P2 is not programmed. In fact, from the start, the RevA consumes 20mA, while the RevB only consumes 6mA! One thing though, is that the graph for RevA shows a lot of peaks and dips. This is not noise or anything, as each data point uses 5 samples, and the electronics on the board, that is being used to take the measurements, are very well filtered. The graph for the RevB board is very smooth, except when the program is calculating big prime numbers between 1000000000 and 1000100000.
P. S.: Mind that the time scale is set in units of 0.1s each (so, 10 points per second, approximately). Will post more results soon!
Kind regards, Samuel Lourenço