Rockbox mail archive
Subject: Re: Use SLEEP instruction for longer (?) runtime
From: Andrew Jamieson (ajamiesn_at_optusnet.com.au)
> Now, that doesn't seem right... the CPU is supposed to draw avg 0.01, max
> 300 *uA* in standby mode! That should make a saving of about 60 mA, not
> 30... Anyone have any ideas what this might be caused by?
It could always be my multimeter, I've certainly been brought low by dodgy
measuring equipment in the past. I dont think it is, but it would be nice
to have someone else replecate the readings (Uwe's readins of 13mA saving
tally pretty closely with mine tho .. ). Other than this; the values given
in the datasheet are typical, and maximum values. No minimum is given. I
would not be supprised to find the current consumption of the SH1 is
somewhat lower than 60mA whilst operating (disregarding any current consumed
by port status), and this causes the difference between the measured 15mA
full sleep, and the documented 20mA.
The standby is strange tho. I couldnt really imagine the standard operating
current of the SH1 being low enough to explain the 30mA discrepency between
measured and documented values. I can only really suggest that the fact
that most of the port pins go to high impedance in standby mode results in
excess current draw elsewhere in the circuit.
> 6k_schematic.pdf still looks wrong when I'm awake. The 12 MHz crystal is
> connected to NMI and WDTOVF, not to EXTAL and XTAL which are three pins
> above NMI and WDTOVF.
The schematics contain many bugs. The guy who drew them up should be shot
I'll trace out the NMI connection on the player, and see if I can see any
source for the excess current draw in standby.
Page was last modified "Jan 10 2012" The Rockbox Crew