RE: MotorCape for the Set of Boards


I was wondering some stuff about the MotorCape that was produced by your company for the set of target boards.

Here goes it.

Why use a barrel jack for the input of power for the Cape and BBB to communicate?

I am not against this idea. I already invested in a dc-dc converter. I am going to wire the barrel jack from dc-dc converter to the battery that supplies the voltage.

I mean, this is my concern. People will not invest in dc-dc converters or buck converters right away, right? I really do not know what other people may do but at times, I am lazy. sys_5v from a power bank is easy-peasey.


P.S. So, if you can find time, please try to understand that I do not want to change things. I would just like to know why it is that the BBB must have power, vdd_5v, via barrel jack instead of the lazy fed power supply of power banks via sys_5v (USB). That is all.

many possible reasons, and unfortunately I would guess that neither you or I will ever find out, because the design requirements are likely to be private between GHI and

it’s also not hard for you to circumvent this without a VREG, using one of the 5v rails, if you think that it is capable of running the device… some solder and wire onto the GND and 5v of your choice, into a barrel plug.

(and just keep in mind that 5v from USB is not that capable of running high current draw devices, it’s a pretty crap source of power in general. Getting better as more devices get USB3 capable, but historically 500mA is the max you could draw reliably, and there’s a lot of old hardware sitting on or under desks that have these USBs)


No issue. I just received my dc-dc converter today. I am going to put a concoction together. Hopefully, 12v battery --> terminals --> wiring --> dc-dc converter --> wiring --> barrel jack, this idea will work out.


You actually can simply add a wire in the female header and things will simply work from the USB connector, making the barrel jack optional. This gives you more flexibility and takes the computer (by default) out of the equation. Not sure which 2 pins need to be connected. I can try to find out from the org or even better bring it up on the beagleboard forum since other users will find this question very useful.

Hello Again Mr. Gus,

Seth here. I found a dc-dc converter to attach a battery. It has a common GND w/ Vin and Vout. There is a pot on it to distinguish the output voltage needed.


P.S. I can keep reading up on the leads needed to make the connection. If you come up w/ the solution, outside of what I am attempting, do not hesitate to reply. Oh and sir, I found some “5v” batteries. I never knew these types of batteries even existed. Odd days.

5v batteries?!!


Yes sir…I am obviously mistaken or my search is coming up empty today. I was going to purchase a bunch of them but now, I cannot find any.

I am most likely wrong. Sorry.


P.S. The closest I came to finding them today was on a site but it was 4.5v.

anyway, it’s totally a silly thing to talk about. We all know that the voltage that a battery has when full is different to what it has at different points in it’s discharge. A “5v” nominal battery (if it existed) may read 4v when mostly discharged. You really have to understand the chemistry of the battery and the cell configuration used. For example the humble 9v “transistor” battery can have multiple chemistries, some of which at maximum voltage aren’t 9v…

Your simplest approach here, because you were using a 12v battery for your motors, is just to wire a 12v to 5v DC converter to the battery, and have the output of that connected to your barrel (or somewhere else if you choose)