When using a bluetooth USB in the IOIO, does it still need the current trimpot adjusted to find the BT USB like it does when connected to the Android phone?

[jparkernr]

The trimpot on my IOIO just spins around with no stops and none of the IOIO sample programs work to turn on the LED.  I've powered the IOIO with a 9v battery and with a dedicated power supply.  I can get the charge indicator on the Galaxy Tab 7 I'm using to show if I play with the trimpot, but it very sensitive and doesn't remain on.  If I use a BT USB, will I still need ot adjust the trimpot?

[Ytai Ben-Tsvi]

Yes. The stoppers on those trimpots tend to break. The trimpot should still work OK, only it will be a little trickier to find the point of least resistance. I recommend the following procedure: turn CW until you have charging and keep turning until you lose charging (passed the point where the stopper should be). Then back off a little until you get charging back.

9V battery is a bad choice for connecting to an Android over USB. It should be fine for BT.

And yes, the BT dongles usually need the trimmer at full-current too.

On Thu, May 17, 2012 at 6:31 AM, jparkernr <park...@gmail.com> wrote:

The trimpot on my IOIO just spins around with no stops and none of the IOIO sample programs work to turn on the LED.  I've powered the IOIO with a 9v battery and with a dedicated power supply.  I can get the charge indicator on the Galaxy Tab 7 I'm using to show if I play with the trimpot, but it very sensitive and doesn't remain on.  If I use a BT USB, will I still need ot adjust the trimpot?

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[jparkernr]

Thanks for the info.  Would it be very difficult to replace the trimpot on the IOIO board.?  Maybe solder on connectors to allow connecting another pot to the board?  The schematics don't show the ohms of the trimpot on the board now.  Do you know what it is?  Thanks.

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[Ytai Ben-Tsvi]

It is 100 ohm I believe.
I don't know whether or not it will be easy for you. Look carefully and judge for yourself... I've soldered this component several times in the past but never with the rest of the components there so I don't know.

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[jparkernr]

I can't use my IOIO for more than a few moments because I lose connection with the phone or BT dongle due to the bad trimpot.  I checked the schematics and touched a lead from the 5v pin on the IOIO to the VBUS pin on the USB connection of the IOIO (left side as you face the opening).  It immediately turned the charge indicator on my tablet.  Can I just wire in a new trimpot from the 5V pin to the VBUS and GND to GND?  Should I cut the old one out?  Thanks.

[Ytai Ben-Tsvi]

There's no gnd. One leg is unconnected, one on vbus, one on 5v. If you don't need current limiting you might as well just short vbus to 5v. Otherwise you better desolder the existing pot and replace it.

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[Vic Wintriss]

When using the ioio board with an Android phone, why do we need a pot?  Why not just connect the vbus to 5v?

[Ytai Ben-Tsvi]

The pot circuit has been introduced to allow limiting the charging current to the Android, mostly in battery-powered applications, where you don't want the Android to drain the main battery. Some Androids take is less well than others, in terms of compromising the connection reliability.

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[Vic Wintriss]

Thanks...I finally understand.  The OTG charging circuit is better.  I don't know why the pot doesn't burn up in the V1 version.  It seems that even minimum charging current will exceed the power rating of the pot.

[Ytai Ben-Tsvi]

The intention was to set it to almost 0 voltage (fully charging) or almost 0 current (fully choked), so that in either case you get very little power dissipation on the actual pot. Indeed, on the OTG I have beefed it up using a FET, but then again, if you're burning real power on the choke circuit you're defeating the purpose for which it was created, which is reducing power draw from the battery.

[Vic Wintriss]

I'm trying to reflash a ioio board with the Pickit 3.  How do I determine which hardware version ioio board that I have?  It seems that PGC and PGD goes to pins 35, 36, 37, 38 or 39?  Which goes with which version

[Ytai Ben-Tsvi]

Can you move this out of this thread, preferably to ioio-dev?