FreeRunner Navigation Board v3 - Power management

Martix martix.cz at gmail.com
Sun May 22 11:44:24 CEST 2011


Hi,

2011/5/21 Christoph Mair <ml at chonyota.net>:
> 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.

Ok, I understand, current can leak through accerometer to GND. But,
this can also happen with VCC connected to AUX, when AUX LED is on.
This could be explanation for NOR u-boot problem.
http://wiki.openmoko.org/wiki/I2C#Powering_additional_I2C_devices

According to http://wiki.openmoko.org/wiki/Freerunner_Navigation_Board#Installation
the AUX power is disabled in suspend. Is this PMU behavior
configurable from software? For example, if I want to wake up Neo
FreeRunner from suspend by IRQ interrupt from Navigation Board.

>> 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..

These pins could by used for current measurement (for example replace
0R by 0.1R and measure voltage drop on it) or for powering peripheral
devices from external sources.
For practical use see:
http://ertos.nicta.com.au/publications/papers/Carroll_Heiser_10.pdf

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

Fortunately, I've found free PMU power output LDO3OUT alias test pin
H-TP1702, which is proper solution for powering expansion
devices/board like this. On the other hand its not easily accessible
as AUX button or accelerometer, because its located near PMU under EM
shielding, but its not impossible to wire it out. (Please, keep this
in mind during GTA04 design process and wire at least one 3V3 power
line outside shielding.)

>> 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
>

Best Regards,

Martix



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