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General suggestions or questions about the SparkFun Electronics website
By antaeus
#95455
Hi, :D
Please I need a little help:
can I power break board to 5 volt? ( it is possible use a 3.3 volt supply like LT1584 ?) :?:
If yes ,have I to get power to pull up GPIO pins from DVDD with a little wire? :?:
Have I to supply optocoupler transistor with 5 or 3.3 volts ( i think 3.3 ) :?:
Thank You for any help
regards

Antaeus
By JMC1965
#95754
Hi antaeus

I've just managed to get this breakout board to work as a little MIDI synth so here's what I've found.

I wanted a small portable midi synth so my power supply consists of 6AA batteries feeding a 5V regulator which itself supplies power to a 3.3V regulator. The breakout board is powered by the 5v supply. The 3.3V supply powers a 6N139 optocoupler for the MIDI input.

I've read about people taking 3.3V off the breakout board itself but wanting to power the optocoupler with 3.3V, to simplify connecting it to the RX pin, I decided on an external 3.3V regulator.

On the breakout board I've made the following connections:-

CS (chip select) to 0V, not really necessary but I've done it anyway.
RST (reset) to 3.3V, this is a must, otherwise IC goes into shutdown mode.
GPIO0 unconnected and GPIO1 to 3.3V, sets IC to Real Time MIDI mode.
GPIO2 and GPIO3 to 3.3V Sets the output volume.

For the audio output I've summed the left and right channel together via a pair of 1K resistors these are then decoupled to the output by a 10uF capacitor (see the FAQ on the Vlsi web site. The output is then taken between the capacitor and 0V.

Hope this helps, if you have any more questions post a message and I'll try to help.

Regards

JMC1965
By antaeus
#95938
Hi JMC1965,
Thank You for the informations.
I think to use an external 3.3 volt regulator too ( I have some LT1584 ).
For audio output I am going to use an OPA like LM358 that works fine
with low voltage.
Maybe a good choice with AA batteries.

Regards

Antaeus
By antaeus
#95940
Hi JMC1965,
When You say:
On the breakout board I've made the following connections:-
You mean that You take 3.3 volt from regulators on breakboard or from external regulator?
I understand that You connected signal to pull up to 3.3V from on board regulators and
use external 3.3v only for optocoupler.
Is it right?
Thank You for your help ( and patience )

Regards

Antaeus
By JMC1965
#95947
Hi Antaeus

I've used the external 3.3V regulator for the opto coupler and the GPIO pins. As long as the 0V on the external regulator and the 0V on the breakout board are connected together this shouldn't be a problem, it also means that you avoid causing any potential harm to the breakout board due to a shaky hand when soldering. I wasn't sure how much current the on board 3.3V regulator could supply which is why I decided to use an external 3.3V regulator.

Regards,

JMC1965
By teprojects1
#200457
antaeus wrote: Thu Mar 11, 2010 2:58 am Hi JMC1965,
Thank You for the informations.
I think to use an external 3.3 volt regulator too ( I have some LT1584 ).
For audio output I am going to use an OPA like LM358 that works fine
with low voltage.
Maybe a good choice with AA batteries.

Regards

Antaeus
Hi,

LM358 is quite a nice option. If you are working on it then you should have a look at LM358 Pinout. It will help you in understanding it better.

Thanks.

Thanks.
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