radio off guarantee?

[Richard A. Smith]

John Watlington wrote:

> While it makes sense to turn off the wireless networking interface on  
> developer

So there's a slight problem with powering off the wireless interface 
from an electrical standpoint.  You can't.
At least not if you want a working system.

WLAN_EN controls WLAN_3.3V. +3.3V is derived from WLAN_3.3V.  So if you
drop WLAN_3.3V you lose +3.3V and you also lose:

VDDIO on the LX700
Pullups on the PCI bus.
Pullups on the jtag lines
Supply voltages for COREPLL, GLPLL, and DOTPLL on the LX700
Power supply to the LX700 Therm alarm circuits
Power supply to the system clock chip.

And lots of other stuff...you get the idea.  System no workie.

That leaves 3 alternatives:

1 Don't load the wlan firmware.
2 Load the firmware and tell wlan xmit to shutdown
3 Hold the WLAN module in reset.

#3 Can be done via the EC but there's currently not a command to _hold_
it in reset.  There is a reset WLAN command which will strobe the reset
line for 1ms.  I can add enable/disable reset commands if 1 and 2 are
not viable.

-- 
Richard Smith  <richard at laptop.org>
One Laptop Per Child