FreeRunner Navigation Board v3 - Power management

[Christoph Mair]

Hi,

Am Samstag 21 Mai 2011, 16:41:06 schrieb Martix:
> How much of power Navigation Board v3 consume, both in operational
> state (all sensors are active) and in idle state (all sensors are
> powered down)? Can I power down whole board from software?
All sensors support a sleep state which reduces power consumption fo a few µA. 
I will add exact numbers to the wiki page. The sleep state is activated 
automatically after power-on. Therefore you have to talk to the sensor to 
activate it. The only exception is the gyroscope ITG-3200. This sensor needs 
the kernel module which will switch it of immediately after the module was 
loaded. If you forget to do this, it will consume about 6mA, IIRC.

> could be board VCC connected somehow to the PMU (PCF50633)? Perhaps,
> Navigation Board could use free power line from PMU, if it's available
> or share power line with one accelerometer or GPS.
I don't know much about the PMU, but I tried to connect the board to one 
accelerometers VCC pin. It works, but I would not recommend it, because the 
I2C lines are pulled up when idle. If the chips do not get powered, some 
current may flows from the bus lines to ground. This could be more that the 
"normal" standby current. But I have to admit that I did not thest this yet.

> I know about test
> pins with 0R resitors on PMU power outputs used for external current
> measurement, VCC could be provided from one of these pads.
I'd like to hear more about these 0Rs..

> Did anybody considered PMU power management approach with Navigation Board?
It should not be needed and could even be a bad idea. See above.

> PS: It would be nice to have some informations regarding power
> management documented on the wiki:
> http://wiki.openmoko.org/wiki/Freerunner_Navigation_Board_v3
I will add some more info. The wiki page lacks a few other updates too.. 
pinout and new pictures, for example.. I will try to fix this tomorrow.

Best Regards,
  Christoph