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 Posted: Apr 15, 2012 - 11:39 AM |
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Joined: Feb 12, 2008
Posts: 771
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So I have found a small board that seems erfect for bluetothing audio from an avr:
http://www.coolcomponents.co.uk/catalog ... p-743.html
however from reading the datasheet it requires 3.3volts AND 1.8volts to power it. I dont quite understand why but on the other hand i dont really have a choice.
So my question is does anyone know where I can get a 1.8volt regulator in england. (not surface mount) Ive checked the normal stores and cant seem to find one.
BTW this board looks fantastic. anyone used it? Ive never seen connections like on it though, they look like sort of semi circles. Can i just use header pins and solder them to the semi circles?
On page 9 of the datasheet is the pin descriptions. I am using pwm to generate audio from a pin of my mega1284, the audio is mono. Do i connect to the left or right of the microphone conenctions or do you think i connect to the pins called PCM_IN - the reason i think PCM is because that is the name of the way the audio is being generated - pulse code modulation?
Thanks guys |
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Posted: Apr 15, 2012 - 11:53 AM |
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Joined: Oct 07, 2002
Posts: 2020
Location: Denmark
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| I had a quick look at Farnell and they have 1.8 V regulators in TO-220 house |
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Posted: Apr 15, 2012 - 01:17 PM |
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Joined: Jul 02, 2005
Posts: 5942
Location: Melbourne, Australia
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| You could "roll your own" with an LM317. |
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Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Apr 15, 2012 - 01:25 PM |
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Joined: Oct 07, 2002
Posts: 2020
Location: Denmark
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or 2 diode drops from 3.3 V (3V)
3.1-0,65*2 =1.8 |
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Posted: Apr 15, 2012 - 01:32 PM |
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Joined: Dec 11, 2007
Posts: 6849
Location: Cleveland, OH
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Well, I'd probably start by bread-boarding the BT to get the circuit up and running properly.
I did not read the data sheet, but you might end up using an op-amp or two to set your input gain, (signal level), and input DC bias, (if any).
That means you have easy access to a simple 1.8V regulator. Just use another op-amp, at least for your testing purposes.
Just make sure that it can source 30 mA, or whatever the current on the 1.8 V supply pin is.
If you used a 10K pot and a 15K fixed resistor, then the Maximum from the pot would be about 2 V. You would set the pot for the 1.8 V you want. (Is Vin 5, or 5.2, etc...).
The upper resistor sets the Max for the pot's output, and essentially decreases the sensitivity of the pot to small adjustments.
Good luck with your project!
JC |
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Posted: Apr 15, 2012 - 10:10 PM |
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Joined: Nov 22, 2002
Posts: 12049
Location: Tangent, OR, USA
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An LM317 does a nice job of it. 2 resistors and two caps.
Jim |
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Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
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Posted: Apr 15, 2012 - 11:25 PM |
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Joined: Feb 19, 2001
Posts: 25912
Location: Wisconsin USA
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Quote:
I dont quite understand why but on the other hand i dont really have a choice.
Interface it to a micro that runs on 3V and internally generates 1.8V and has an "out" pin. |
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Posted: Apr 16, 2012 - 01:23 PM |
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Joined: Oct 20, 2005
Posts: 258
Location: Colorado
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As far as feeding audio in to the part, I would put it in both the right and left so audio will come out both right and left. Though you could choose just the right or just the left. This really depends on your overall design goals.
PCM does NOT equal PWM, FYI. |
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Posted: Apr 16, 2012 - 10:38 PM |
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Joined: Feb 12, 2008
Posts: 771
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Quote:
Interface it to a micro that runs on 3V and internally generates 1.8V and has an "out" pin.
How do you get it to do that? surely I can generate "high" or "low"? How do I get a pin to only be 1.8v? If i can i'll just set a pin to 1.8v off my m1284 and that'll generate my power supply... |
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Posted: Apr 17, 2012 - 03:03 AM |
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Joined: Jul 02, 2005
Posts: 5942
Location: Melbourne, Australia
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I think that you have misunderstood Lee's suggestion. Some micro's have an internal bandgap reference voltage and associated amplifier's that can be configured to deliver one of several reference voltages at their AVref pin.
Cheers,
Ross |
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Ross McKenzie
ValuSoft
Melbourne Australia
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Posted: Apr 22, 2012 - 09:04 PM |
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Joined: Feb 12, 2008
Posts: 771
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So could I use a diode to drop 3volts to 2.3 then a resistor to drop it another .5v? I just want to keep this as small as possible.
I havent completely worked out how my resistor circuit would be but I think you could do that couldnt you? |
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Posted: Apr 22, 2012 - 11:37 PM |
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Joined: Feb 19, 2001
Posts: 25912
Location: Wisconsin USA
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Quote:
off my m1284
So, NOW we have further requirements? Nowhere in the thread can I see a mention of an AVR model.
Quote:
Some micro's have an internal bandgap reference voltage and associated amplifier's that can be configured to deliver one of several reference voltages at their AVref pin.
Some micros that run at 3.xV raw supply run internally at 1.8V core, and have 1.8V on one or more pins. |
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