FreeRunner Navigation Board v3 - Power management

Christoph Mair ml at
Sun May 22 14:08:55 CEST 2011

Am Sonntag 22 Mai 2011, 11:44:24 schrieben Sie:
> Hi,
> 2011/5/21 Christoph Mair <ml at>:
> > 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.
I mostly use power from the AUX switch. With the FRNBv3 I did not encounter 
the NOR u-boot problem yet. Everything seems to work fine. If someone 
encounters a problem, there are solderpads for additional capacitors on the 
bottom side to fix evantual issues.

> According to
> 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.
You got that wrong. The AUX power is always available, just the power to the 
accelorometers is shut down in suspend. If you grab your VCC from the 
decoupling cap of the accel, all sensors will be switched off.

If you want to weak the FR using a IRQ triggered from the FRNB, you need an 
additional wire to connect one sensor to a IRQ line on the FR. Since v3, all 
interrupt outputs of the sensors are available on (tiny) testpoints.

> 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. 
I did not try this yet.

> (Please, keep this
> in mind during GTA04 design process and wire at least one 3V3 power
> line outside shielding.)
Depending on measurement results, we may do not need a shield and there are 
testpoints which you can use to power additional electronics.

> >> PS: It would be nice to have some informations regarding power
> >> management documented on the wiki:
> >>
I will add more information when I can test the first machine assembled board.

Best regards,

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