Attaching accessories (was: OpenMoko Challenges

Richard Bennett richard.bennett at
Tue Feb 13 01:23:29 CET 2007

On Monday 12 February 2007 16:15, Nils Faerber wrote:
> Richard Bennett schrieb:
> > On Monday 12 February 2007 13:05, Nils Faerber wrote:
> >> - not even counting in the extreme high power consumption it would
> >> cause. I assume unless some genious invents a much higher efficient step
> >> up converter you will not see any small portable device to support bus
> >> powered USB devices.
> >
> > One way would be for FIC to supply an optional fatter replacement battery
> > that included one extra 1.5v cell, a wifi dongle, and the necessary
> > circuitry for charging the additional cell after the regular ones were
> > full, and supplying the 3.3 / 5v outlets.
> Uh... quite tough, isn't it?
> That would require a major hardware work (second charger logic for 5V
> charging, power switch, more pins in the battery pack, extra power
> regulator for 5V, etc.). That would mean roughly an addition of 20 to 40
> extra parts on the PCB. Sure, could be done, but is a quite complex
> thing. IMHO too complex to achieve the goal.
No no.
(I should add I'm not a OEM hardware expert, but do have a background in 
My suggestion would not require any changes to the phone's PCB, and the 
original phone would be shipped with a normal battery.
People wanting to attach additional accessories to their phones face some 
* There is no 5v power supply.
* Anything you connect will empty your battery pretty fast, especially when 
stepping up to 5v from 3.3 v.
* Having battery powered usb hubs and dongles hanging of the bottom of your 
phone is pretty ugly.
* Charging over USB and running accessories over USB at the same time is not 
* Clip-on sleeves that you slide onto the phone from the bottom might work for 
some of the issues, but are fragile and make the phone unwieldy, and don't 
solve the power problem, unless they are very large with their own 5v 
* Some solutions require changes to the original PCB.

Using the replacement battery suggestion solves all of these issues:
It should be possible to keep it about 8mm fatter than a regular battery at 
most, so although the phone gets quite fat, it is better than having all 
kinds of stuff hanging off the bottom.   
The battery itself is basically a smart framework, without any inherent 
function, and can then be augmented with one or more 'payloads' depending on 
what the user requires.
Payloads could be: Wifi dongle, USB hub, Infrared eye, RFID Scanner, barcode 
reader, environmental sensors, car interface, audio breakout box, hard 
The payload could communicate with the phone through the mini SD socket inside 
(might require a flat-cable connector), or through an external loop to the 
USB socket.
The Battery could contain 1 extra 1.5v volt cell, together with the regular 
capacity cells that can provide 5 volts to the payload through a regulator in 
the battery, and added battery-life. And if the battery is finished the user 
can click-on their original battery again.
It can contain it's own charging circuit that charges the original batterypack 
first, and then switches to charging the 1.5v cell when the normal cell is 
full, so the phone's own charging circuit needs no changes.
I think this would solve all those 'why doesn't the phone have a built-in 
toaster' questions, and it could also be sold without payload, so hardware 
hackers could add their own sensors etc in.

> I am personall already quite happy with Bluetooth. 
So am I, I wasn't focussing on wifi, but was looking for a broader solution to 
the lack of 5v, and many additional sensors and features people are asking 


> Cheers
>   nils faerber

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