KF OTG Discussion

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altitude909

Senior Member
Apr 13, 2011
270
45
Walled Lake, Michigan
So I have been playing around with various USB game controllers as well as various storage devices and everything has worked so far (except BT, its detected but thats it). Hashcode has put a low priority on OTG in the kernal dev queue so I would like to get a discussion going about possible hardware solutions to over come the current 3.3v limitation of the USB port when running as a host (which is why devices dont work directly, only through a hub). Someone already suggested a current pump DC-DC in the kernal thread so my current focus something like this: http://www.circuitsathome.com/dc-dc/33v-to-5v-dc-dc-converter

for some motivation to this end, here is my USB NES controller hooked via OTG:

 

meturne2

Senior Member
Feb 22, 2012
69
8
Can the voltage regulator be wired into the OTG cable? If so I am willing to try this but I need help with the wiring. I am searching now for some type of soapbox enclosure to house the voltage regulator. Any suggestions?
 

altitude909

Senior Member
Apr 13, 2011
270
45
Walled Lake, Michigan
It would serve as the otg cable. The vreg will sit on the power rail between the kf and the normal usb connector. Ultimately, i want to lay out a smd board with the micro usb and regulator that goes in some little enclosure.
 

meturne2

Senior Member
Feb 22, 2012
69
8
Basically what I am thinking of doing is putting the regulator inbetween the micro usb and female usb. It will look like other otg cables but the enclosure with the female usb will be larger.

I am assuming that the red(power) from micro usb is connected to the vout and the red(power) from female usb is connected to vin on the regulator. Do both sides of the ground need to be connected to the regulator or just to each other?
 

altitude909

Senior Member
Apr 13, 2011
270
45
Walled Lake, Michigan
Basically what I am thinking of doing is putting the regulator inbetween the micro usb and female usb. It will look like other otg cables but the enclosure with the female usb will be larger.

I am assuming that the red(power) from micro usb is connected to the vout and the red(power) from female usb is connected to vin on the regulator. Do both sides of the ground need to be connected to the regulator or just to each other?

You could but IMHO, it would be simpler and cheaper to integrate everything as one device. The OTG cable is nothing special, just a micro USB B to regular USB A. The power needs to run from the micro in the KF to the vReg Vin, vReg Vout to the USB A connector, the ground is connected to all three.

Can this work with GPS receiver?

sent from the greezals fire.

No clue. I'm sure a google search would yield some answers
 

altitude909

Senior Member
Apr 13, 2011
270
45
Walled Lake, Michigan
Ok, the ones I ordered are in. Size is NICE, it should be really easy to integrate this into existing USB connector enclosures. This is the 120 mA version, the 600 mA version is about twice the size

vreg.jpg
 
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barrmulio

Senior Member
Oct 5, 2010
357
359
Ok, the ones I ordered are in. Size is NICE, it should be really easy to integrate this into existing USB connector enclosures. This is the 120 mA version, the 600 mA version is about twice the size

vreg.jpg

very nice - i ordered the pololu one and still waiting for it to arrive

my thoughts were similar; integrate the regulator into the usb female header area of the otg, or somewhere mid-cable...but I'm having a hard time finding an elegant solution to either re-enclosing the plastic end of the female header or enclosing it mid cable

i just back another otg cable today, i'll be cutting it apart to see if there's enough space by the usb a
 

altitude909

Senior Member
Apr 13, 2011
270
45
Walled Lake, Michigan
success! kinda.. For super low current devices (i.e. NES game controller) it is working fine, anything larger (flash memory) its drawing too much current causing the voltage to sag below 2.5V which is not enough to power the regulator. Will try the LTC3426 one tomorrow since that should be able to operate at a lower input voltage

otgkf.jpg
 

barrmulio

Senior Member
Oct 5, 2010
357
359
success! kinda.. For super low current devices (i.e. NES game controller) it is working fine, anything larger (flash memory) its drawing too much current causing the voltage to sag below 2.5V which is not enough to power the regulator. Will try the LTC3426 one tomorrow since that should be able to operate at a lower input voltage

just to make sure I got your wiring right
from micro usb b
- red to vReg Vin
- pin 4 to ground
- pin 5 to ground

from usb a
- red to vReg Vout
- black/pin 4 to ground

?
my stupid otg cable doesn't have standard colors (it's green, blue, yellow, red, yellow&red), so other than vcc i'm not sure what's what (edit: now i think blue is gnd and yellow/red is sense, yellow is d-, green is d+).

I was also expecting the otg short to be on the micro side and not on the usb a side, but it wasn't

my idea is to have the regulator sit inside the hollowed out area of the female header seen on the bottom left

5y7li.jpg
 
Last edited:

altitude909

Senior Member
Apr 13, 2011
270
45
Walled Lake, Michigan
Just take a meter and see what is connected to what. It does not matter where pin 4 and 5 are shorted.

Unfortunately, it looks like without some sort of magic, the port on the kf cannot supply enough current to drive these regulators. Im observing the same thing as southbird did, the devices show up but do not work. Measuring the voltages at the power pins with a flash drive connected i get 2.4v at the vreg input and 4.5 at the output which means that there is too much load. Time to start looking for battery powered usb hubs
 
Last edited:

barrmulio

Senior Member
Oct 5, 2010
357
359
ok, the regulator arrived today and i played around with it

the otg cable was too frail for my poor soldering skills to do properly, so i ended up cutting up a usb extension cable to about 1' in length and soldering it halfway...i'll enclosure in heat shrink later

my results were pretty much the same as southbird and altitude909

My 8Gb centon usb however mounts perfectly *every* time, however my 4Gb, 2Gb or 512Mb sticks will not mount. When I try the elago w/ a 32Gb micro it conks out mounting as a whole, requiring a reboot of the KF to remount the 8Gb stick (probably some kernel protection)

QloMD.jpg


Z1hCN.jpg
 

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    Ok, the ones I ordered are in. Size is NICE, it should be really easy to integrate this into existing USB connector enclosures. This is the 120 mA version, the 600 mA version is about twice the size

    vreg.jpg
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